^fco s*.
>y
-------
EPA-550/9-74-017
BACKGROUND DOCUMENT
FOR
INTERSTATE MOTOR CARRIER NOISE
EMISSION REGULATIONS
OCTOBER 1974
PREPARED BY
U.S. Environmental Protection Agency
Washington, D.C. 20460
This document has been approved for general
availability It does not constitute a standard,
specification or regulation.
-------
TABLE OF CONTENTS
Page
SECTION I. EPA STRATEGY FOR CONTROL OF MEDIUM AND
HEAVY DUTY MOTOR VEHICLE NOISE . 1
Noise Levels Protective of Public Health and Welfare 1
Actual Noise Levels in Residential Areas 3
EPA Regulatory Strategy for Motor Vehicles 3
Rationale for the Coverage of Vehicles Over 10,000 Pounds
GVWR/GCWR 6
SECTION 2. TECHNOLOGY AND COST OF QUIETING IN-SERVICE
MOTOR VEHICLES 8
General Characteristics of Large Trucks 9
Component Noise Sources and Quieting Techniques ........ 10
Exhaust System 14
Cooling Fan 15
Engine (Mechanical) 16
Air Induction System 17
Tire/Roadway Interaction IB
Cost of Retrofitting Individual Trucks 19
Technology and Cost Required to Comply with a Low-Speed
Standard 21
Technology and Cost Required to Comply with a High-Speed
Standard 25
-------
TABLE OF CONTENTS (CONT)
Page
SECTION 3. INTERSTATE MOTOR CARRIER REGULATIONS ... 27
Summary of the Regulations 27
Revision of the Proposed Regulations Prior to Promulgation ... 2b
Preemption 32
Enforcement Procedures, Violations, and Penalties 35
Relationship between Low-Speed Measurement Procedures .... 36
Stationary Run-Up Test Correlation with SAE «J366a 42
SECTION 4. NOISE MEASUREMENT OF IN-SERVICE VEHICLES.. 44
Measurement Methodology ^4
Surveys of Truck Noise 46
Analyses of High Speed (Over 35 MPH) Survey Data 47
Analysis of Low Speed (Under 35 MPH) Survey Data 56
Analysis of Stationary Runup Test Data 56
Classification of Trucks into Categories 59
Potential Degradation of Vehicles 52
SECTION 5. IMPACT OF THE FEDERAL NOISE REGULATIONS. . 6-1
Economic Impact of the Regulations 64
Environmental Impact of the Noise Emission Standards 66
Relative Stringency of Federal Regulations and Those of Other
Jurisdictions 68
ii
-------
TABLE OF CONTENTS (CONT)
Page
REFERENCES 72
APPENDIX: MEASUREMENT METHODOLOGY 76
Applicable Documents 76
Instrumentation 76
Calibration 77
Standard Measurement Site 77
Weather 73
78
Microphone Location
Noise Measurement Procedures 78
iii
-------
Section 1
EPA STRATEGY FOR CONTROL OF MEDIUM AND HEAVY DUTY
MOTOR VEHICLE NOISE
In March, 1974, in accordance with Section 5(a)(2) of the Noise Control
Act of 1972, EPA published a document in which levels of environmental noise
requisite to protect public health and welfare were identified* '. Since EPA
studies have shown that actual environmental noise levels in many parts of
the country exceed tl.^ .3vels identified as desirable, a Federal strategy is
being developed to control environmental noise.
NOISE LEVELS PROTECTIVE OF PUBLIC HEALTH AND WELFARE
As part of the Identification of noise levels protective of public health and
welfare, EPA has selected the noise measures it believes are most useful for
describing environmental noise and its effects on people.
Environmental noise is defined in the Noise Control Act as "the Intensity,
duration and the character of sounds from all sources. " The measures for
characterizing environment noise must, therefore, evaluate these factors.
However, the measures must also predict human response and be simple to
monitor if they are to be useful. EPA has chosen two cumulative equivalent
sound level measures as its basic indicators of noise that constitutes a long-
term hazard to public health and welfare. The first measure is the equivalent
sound level {L ), which is the constant sound level (dBA) that in a given situa-
tion and time period would convey the same sound energy as does the actual
time-varying sound; L is used as an indicator of long-term hazard to hearing.
A variation of L , the day-night sound level (L, ) is the equivalent sound level
during a 24 hour period with a 10 dB(A) penalty added to events occurring
between the hours of 10 p.m. and 7 a.m. to account for the increased annoyance
caused by noise at night; L, is used as an indicator of long-term annoyance.
-------
The relationships between environmental noise and human response have
been quantified using the simple measures described above. The human
response examined was a combination of such factors as hearing interference,
sleep interference, speech interference, desire for a tranquil environment
and the ability to use telephones, radios, and TV satisfactorily.
The levels identified by EPA as desirable from a public health and welfare
viewpoint are predicated on minimizing the average number of pe ^le who may
experience an adverse reaction to noise as a result of extended exposure.
However, different individuals do not have the same susceptibility to noise.
Even groups of people may vary in response depending on previous exposure,
age, socio-economic status, political cohesiveness and other social variables.
In the aggregate, however, the average response of groups of people is predic-
table and related to cumulative noise exposure as expressed by L . or L .
Detailed discussions of the relationships between environmental noise and
human response is provided in the EPA document Information on Levels of
Environmental Noise Requisite to Protect Public Health and Welfare with an
Adequate Margin of Safety. Desirable outdoor noise levels are summarized in
Table 1 in terms of yearly equivalent levels which, if not exceeded, would be
safe from a health and welfare viewpoint. Public health and welfare for the
purpose of this analysis was defined so as to include personal comfort, well-
being, and the absence of clinical symptoms.
TABLE 1
SUMMARY OF NOISE LEVELS IDENTIFIED AS REQUISITE TO PROTECT
PUBLIC HEALTH AND WELFARE WITH AN ADEQUATE MARGIN OF SAFETY. (2)
Effect Level in dB Area
Hearing Lea(24l ~ 70 ^ Areas
Loss
Activity Interference L . £ 55 Residential
Outdoors Areas
-------
ACTUAL NOISE LEVELS IX RESIDENTIAL AKEAS
Studies have been performed to measure the noise levels in residential
areas and to estimate the number of people subjected to noise in those areas.
Table 2 contains estimates of the number of people residing in urban areas
which are exposed to noise principally caused by urban traffic, freeway
traffic, and aircraft operations.
TABLE 2
ESTIMATED CUMULATIVE NUMBER OF PEOPLE IN MILLIONS
IN THE UNITED STATES RESIDING IN URBAN AREAS WHICH ARE EXPOSED
TO VARIOUS LEVELS OF OUTDOOR DAY/NIGHT AVERAGE SOUND LEVEL<
Outdoor
L, Exceeds
on
60
65
70
75
80
Urban
Traffic
59.0
24.3
6.9
1.3
0.1
Freeway
Traffic
3.1
2.5
1.9
0.9
0.3
Aircraft
Operations
16.0
7.5
3.4
1.5
0.2
Total
78.1
34.3
12.2
3.7
0.6
The data in the table clearly indicate that motor vehicles are the principal
source of environmental noise in urban areas.
EPA REGULATORY STRATEGY FOR MOTOR VEHICLES
Accordingly, EPA has developed a regulatory strategy that places high
priority on the control of motor vehicle noise. As part of the development
of the strategy, studies were performed for EPA that provide information
on the relative noise contribution of different kinds of motor vehicles to
traffic noise levels in urban areas. Table 3 gives information on the typical
sound level at 50 feet of seven types of motor vehicles and also indicates the
-------
estimated total daily sound energy emitted into the environment by all in-
service vehicles of each type. For the purpose of the analysis, trucks and
automobiles were divided into groups having different noise emission and
technology characteristics. Light trucks were separated from medium and
heavy duty trucks because they have a higher power-to-weight ratio and are
quieter in normal operation. Large passenger cars were separated from
compact and sports cars for the same reason.
Motor Vehicles
TABLE 3
Typical Sound Level
dB (A) at 50 feet
Estimated Total
Sound Energy
KW-Hrs/Day
1.
2.
3.
4.
5.
6.
7.
Trucks (medium & heavy)
Automobiles (sports, compacts)
Automobiles (passenger)
Trucks (light, pickup)
Motorcycles (highway)
Buses (city and school)
Buses (highway)
84
75
69
72
82
73
82
5800
1150
800
570
325
20
12
The sound level (dB(A)) at 50 feet is a measure that suggests which motor
vehicles will be perceived as noisy by the community when they are operated
alone. The daily total sound energy emission is useful because it is an
aggregate measure that takes into account the sound energy emission rate of
the vehicle, the number of vehicles operating, and the amount of time they
are operated each day. Neither measure directly relates human exposure or
response to the vehicle's noise emission; but when several kinds of vehicles
are operated in similar situations, these two measures serve to indicate which
are the major sources of noise.
-------
The data in Table 3 clearly indicates that medium and heavy duty trucks
contribute more sound energy to the environment than any other type of high-
way vehicle and that an individual truck will typically be perceived to be
louder than some other type of motor vehicle. These values are a composite
of noise emitted in both urban traffic conditions and on freeways, and there
can bo little doubt that medium and he.ivy duty trucks are the major contributor
to trail'ic noise in many situations.
The Noise Control Act contains two sections of primary importance for
the control of motor vehicle noise. Section 6 contains authority by which EPA
may promulgate product noise emission standards for new motor vehicles
that are applicable rsl Ihc time of sale of such vehicles.
Section 18 of the Act requires EPA to promulgate noise emission regula-
tions that include ''noise emission standards setting such limits on noise
emissions resulting From operation of motor carriers engaged in interstate
commerce which reflect the degree of noise reduction achievable through the
application of the best available technology, taking into account the cost of
compliance."
Accordingly, EPA has developed and is now implementing a motor vehicle
noise control strategy based on sections 6 and 18 of the Act that should prove
to be effective in reducing environmental noise in many areas to the levels
identified as protective of public health and welfare. The strategy calls first,
for the reduction, within one year of the promulgation of these regulations under
section 18, of the noise from vehicles over 10,000 pounds GVWR/GCWR oper-
ated by motor carriers engaged in interstate commerce, to the lowest noise level
consistent with the noise abatement technology available for retrofit application
during the one year period, taking into account the cost of compliance.
Subsequently, under section 6, new product noise emission standards will
be proposed for medium and heavy duty trucks, and it is contemplated that
the new product standards will be maintained for new trucks beyond the initial
point of sale through subsequent modification of these initial Interstate Motor
Carrier Regulations pursuant to. section 18 to require that vehicles manufactured
-------
to comply with new product performance standards and used in interstate com-
merce shall maintain the lower noise emission levels during operation.
Additionally, it is anticipated that the performance standards in the inter-
state motor carrier regulations relating to older vehicles will be made more
stringent as more advanced retrofit technology becomes available ana Ih cost
of compliance permits.
The effect of the initial Interstate Motor Carrier Regulations via be
noticeable principally around highways. The principle noise reduction will be
of the intrusive "noise peaks," which have been widely acknowledged as more
objectionable to people than much lower levels of continuous noise' . However,
the reduction of traffic noise to levels protective of public health and welfare is
not feasible through retrofit programs alone and must await the replacement of
the current vehicle population by new quiet vehicles in conformance with noise
standards promulgated under Section 6.
RATIONALE FOR THE COVERAGE OF VEHICLES OVER 10. OOP POUNDS GVWR/GCWR
Prior to proposing regulations applicable only to vehicles over 10,000 pounds
GVWR/GCWR, the Agency analyzed both the relative noise contribution to traffic
noise levels and the typical use patterns of different kinds of motor vehicles.
Light trucks and automobiles were separated from medium and heavy duty trucks
for the analysis because they have a higher power-to-weight ratio, they are
quieter in normal operation, and they have different uses than larger vehicles.
In addition to their higher noise emissions, medium and heavy duty motor
vehicles are distinguished from lighter vehicles by their typical use for long
distance intercity and interstate hauling. They are, therefore, operated many
more miles per year on the average than light duty vehicles, which are normally
used for general service and delivery work within a relatively small area.
Medium as well as heavy duty motor vehicles operated by interstate motor
carriers are in significant numbers constantly in transit between different
jurisdictions, and it would be impractical for them to comply with a different
noise emission standard in different jurisdictions. Thus, "medium duty" as
-------
well as "heavy duty" motor vehicles operated by interstate motor carriers
are construed by the Agency to be "major noise sources in commerce control
of which require uniform national treatment" under section 18 of the Noise
Control Act.
Conversely, since light duty vehicles are typically used for general
service and delivery work within relatively small areas and are not usually
subject to the noise emission regulations of many different jurisdictions,
national uniformity of treatment of the noise emission resulting from their
operation does not appear essential at this time.
The specification of a precise delineation between "light duty" or "small"
vehicles and "medium and heavy duty" vehicles for purposes of regulation is
largely an exercise of technical judgment. EPA has chosen to make that deline-
ation at 10,000 pounds GVWR/or GCWR in these regulations.
A break at 10,000 pounds GVWR/GCWR is also convenient because most states
use that weight rating as a distinction in their vehicle registration categories.
The Department of Commerce and the Motor Vehicle Manufacturers
Association divide light duty and medium duty vehicles at that weight rating.
In addition, it is a standard weight category distinction used by the Department
of Transportation in their safety regulations, and compatibility of the Inter-
state Motor Carrier Regulations with the present DOT weight categories is
advantageous because DOT is the Federal enforcement agent.
-------
Section 2
TECHNOLOGY AND COST OF QUIETING IN-SERVICE MOTOR VEHICLFS
Section 18(a)(l) of the Noise Control Act requires that noise emission
standards pursuant to that part set limits on noise emissions resulting from
the operation of motor carriers which "... reflect the degree of noise
reduction achievable through the application of best available technology,
taking into account the cost of compliance."
In order to implement this section of the Act, "best available technology"
and "cost of compliance" have been defined as follows:
"Best available technology" is that noise abatement technology
available for retrofit application to motor vehicles that produces mean-
ingful reduction in the noise produced by vehicles used by motor carriers
engaged in interstate commerce. "Available" is further defined to
include:
1. Technology applications that have been demonstrated and can be
retrofitted on existing motor vehicles.
2. Technology for which there will be a production capacity avail-
able to produce the estimated number of parts required soon
enough to allow for distribution and installation prior to the
effective date of the regulation.
3. Technology that is compatible with all safety regulations and
takes into account operational considerations, including mainte-
nance, and other pollution control equipment.
"Cost of compliance" means the cost of identifying and carrying out
the action that must be taken to meet the specified noise emission level,
including the additional cost of operation and maintenance.
Discussion of the technology and cost required to achieve specified noise
emission levels must be based on an understanding of the sources of motor
vehicle noise. This section describes the noise characteristics of large
-------
motor vehicles, the technology available, and the cost of achieving noise
reduction. It specifically discusses multiaxle diesel trucks because (1) they
make the most noise, (2) most of the available data relate to these trucks,
and (3) any regulation which is feasible for such trucks will also be feasible
for other large vehicles.
The noise produced by a truck depends on the type and the quality of its
component parts. Large trucks are not standardized as are automobiles.
Specialized user needs result in a greatly varied assembly of components,
especially with respect to power train and related equipment. As a result,
truck noise can vary considerably from vehicle to vehicle. To illustrate the
extent of this variation, the discussion of noise sources below is preceded
by a brief description of truck components.
GENERAL CHARACTERISTICS OF LARGE TRUCKS
Diesel engines may be naturally aspirated (air introduced at atmospheric
pressure), turbocharged, or supercharged by the engine itself. The engine
can be located either at the front of the cab (in "conventional" trucks) or under
the cab (in "cab-over-engine" trucks).
Exhaust pipes may be routed horizontally underneath the body of the
vehicle or vertically to the rear of the cab - commonly referred to as a
"straight stack". A straight stack is usually preferred, because it directs
exhaust fumes away from motorists and pedestrians. Either single or dual
exhaust systems may be installed. The engine intake may be situated on or
under the hood in a conventional style truck or to the rear of the cab in either
the conventional or the cab-over-engine (COE) style. If it is behind the cab,
it may be on the same or opposite side of the cab as the exhaust system.
The power-to-weight ratio for a fully laden truck is significantly less
than that for an automobile, with the result that the necessary torque must
be transmitted through a wide range of gears - up to as many as 15. The
torque is usually applied to either one or two drive axles. The number of
axles on the entire vehicle, including the trailer, can range from 2 to 11, the
limit varying according to state regulations. In general, the greater the
-------
number of axles, the greater the load-carrying capacity of the truck. Corre-
sponding in part to the number of axles, the number of tires on a heavy truck
trailer combination can range from 10 to 42.
Figure 1 shows the effect of vehicle speed and engine rpm on engine
noise at 25 ft. However, noise from the propulsion system is not the only
contributor to the overall noise level. At speeds greater than about 45 mph,
additional noise of significant magnitude is produced by the ir -raction
between the tires and the road surface* '. The relationship between pro-
pulsion system noise and tire noise as a function of vehicle speed is shown
in Figure 2* ' '. The speed at which tire noise begins to dominate depends
primarily on the type and number of tires on the truck, the degree of tire
wear, tire load, type of pavement, and tire inflation pressure* '.
COMPONENT NOISE SOURCES AND QUIETING TECHNIQUES
The total noise level produced by a truck is the logarithmic sum of the
individual noise levels produced by several different components. These
component noise sources, shown in Figure 3, are as follows (not necessarily
(9)
in order of importance)
Exhaust system
Engine cooling fan
Engine (mechanical)
Air intake system
Transmission (gearbox, drive shaft, rear axles(s))
Auxiliary engine equipment
Tire/roadway interaction
Aerodynamic flow
Brakes
The first four sources are of major importance for the trucks of concern
here when they are traveling at low speeds (less than 45 mph)* . As
Figure 2 shows, at higher speeds (greater than 45 mph), tire noise assumes
a much greater significance. A brief discussion of these major sources is
contained in the following sections.
10
-------
100
90
1 I
Maximum Engine Speed
I I
o
CD
0)
2>
O
70
60
I
I
I
100
7 8 9 10 15 20
Vehicle Speed, mph
30
40 50
a.
o
CM
n
TT
00
I- 80
3!
5
* 7°
i
60
1000
48 mph
8 mph
I
I
I
2000 3000 4000
Engine Rev./Mm.
Microphone 7.5 Meters (25 Feet) From Center!me of Vehicle's Path
Figure 1. Propulsion System Noise Versus Vehicle Speed and Engine Speed
-------
100
Tire Combinations
Steering Axle
o New Ribs
o New Ribs
A New Ribs
Drive Axles
V, Worn X-Bars
New X-Bars
New Ribs
Trailer Axles
New Pockei Retread
New Rib Retread
New Rib Retread
90
Engine Related Noise Alone
Thru 12 Gear Steps
m
a
«
8
o
c
80
70
60
10
20 30
Vehicle Speed, mph
40
50
Figure 2. Propulsion System and Tire Noise for a
Typical 5 Axle Tractor Trailer (from
reference 6 and 7)
12
-------
B
Major Noise Sources
A. Engine (Mechanical)
B. Engine Cooling Fan
C. Engine Exhaust
D. Air Intake System
Other Sources
E. Transmission
F. Ancillary Equipment
G. Tire/Roadway Interaction
H. Aerodynamic Flow
I. Brakes
Conventional (C) Cab
Cab-Over-Engine (COE)
Figure 3. Truck Noise Sources and Cab Types
-------
KXMAUh'l SYSTEM
Exhaust noise is created when engine exhaust gases cause oscillations
within the exhaust pipe. These oscillations are radiated to the atmosphere
at the tail pipe. The noise is a function of engine type, induction system,
exhaust system, and other associated parameters* '. In addition lo i
radiated from the end of the tail pipe, exhaust noise is transmitted througu
the exhaust pipe and muffler walls. Noise is also produce'1 by the applica -
tion of engine brakes (on trucks so equipped), which assist the wheel brakes?
by producing a retarding force on the engine. Typical exhaust noise levels
range from 77 to 85 dB(A) at 50 ft, independent of vehicle speed' ', and
can be much higher in trucks which have been poorly maintained.
Although the exhaust system is a major noise source, significant noise
level reductions can be achieved fairly easily. A good muffler is mandatory,
and for maximum quieting, a double-wall or wrapped muffler can be used to
reduce radiation through the walls. Consideration can also be given to
wrapping the tail and exhaust pipes with insulation. The system must be
free from leaks and should be attached by isolation mounts to the truck frame.
The location of the muffler in the overall system, the exhaust pipe length,
and diameter, and the tail pipe length and diameter should be considered,
although these factors assume a gradually lessening importance as the
attenuation capability of the muffler increases. Muffler specifications and
suggested exhaust system configurations are currently offered by major
muffler manufacturers for almost every engine, although no universal
muffler exists which is the best for all types of engines.
Exhaust noise alone from trucks equipped with the best available mufflers
typically ranges from 72.5 to 80 dB(A) at 50 ft. These mufflers provide
attenuation of from 9. 5 to 27 dB and are installed on some new trucks as
(12}
standard equipment* '. A good quality muffler typically costs from $35
to $45, and since the installation is simple, many trucking companies do it
themselves. Installation costs for either single or dual systems are about
$15* ' . For maximum effect, it is necessary to replace existing flexi-
ble exhaust pipes with rigid pipe and slip joints at a cost of about $45 per
side including labor.
14
-------
COOLING FAN
Trucks generally use axial fans to draw air through a front-mounted
radiator. The air cools water which in turn cools the engine. Fan noise
is the result of air flow irregularities and is partially governed by the
(15)
proximity of shrouds, radiators, grills, and radiator shutters * ;. The
noise produced by the fan is related to fan tip speed. Most diesel engines
on heavy trucks reach maximum rated horsepower at about 2100 rpm. At
this speed, the fan can be a major contributor to the overall truck noise
level. Typical truck fans alone exhibit noise levels in the range of 78 to 83
dB(A) at 50 ft at rated engine speed* '.
Since noise from a cooling fan increases with the rotational speed, it
is possible to reduce the noise while maintaining the same air flow (to
satisfy the same cooling requirement) by using a larger fan turning at a
slower speed. In many cases this may require the installation of a larger
radiator, which could result in an expensive modification to the front of the
engine compartment.
It is often possible to install a fan blade that produces less noise while
at the same time providing adequate cooling. Most existing fans are stamped
out of metal with equal spacing between the blades, and they are driven at a
predetermined fixed ratio of fan-to-engine speed by a belt-driven pulley.
This type of fan was not originally designed to be quiet, nor is it particularly
efficient in performing its task. In many cases, it can be replaced with a
more sophisticated design that affords a fan noise (not total truck noise)
reduction of from 7 to 12 dB^ \ The cost is in the range of $40 to $35
including installation* ^. Overall truck noise can also be reduced by about
1 dB in some cases by incorporating a venturi-type shroud with a small tip
clearance, at a cost of about $45 including installation.
15
-------
Trucks are designed to be able to cope with heat rejection at maximum
engine power with little or no ram air. Since ram air increases with vehicle
speed, fans become less important at higher vehicle speeds and could be
slowed or stopped in many instances, The critical cooling requirement occurs
when the truck is moving slowly in a low gear but the engine is developing full
horsepower (e.g. when pulling a heavy load up a long grade). Trucks, un-
like automobiles, usually do not have an overheating problem when the
vehicle is stopped and the engine idles at low rpm. Given these character-
istics, it is possible for a truck to have a fan which does not operate
continuously.
Fans are now available which operate only when additional engine cooling
is required and which idle when the cooling due to ram air flow is sufficient.
A typical fan of this type has either a thermostatically controlled mechanical
clutch or a viscous fluid clutch. The viscous fluid clutch permits the fan to
rotate at reduced speeds and the thermostatically controlled mechanical
clutch permits the fan to stop completely when not needed. Fans utilizing
these clutches are about 3 to 10 dB quieter than conventional fans' .
A viscous clutch costs about $240 including about $15 for the suggested
fan blade. A thermostatically controlled mechanical clutch including the
necessary fittings costs from about $285 to $360, plus $40 to $50 for
installation*20» 21).
ENGINE (MECHANICAL)
Mechanical noise in internal combustion engines is caused by the
combustion process, which produces the high gas pressures necessary to
force the piston down the cylinder and turn the crankshaft. The rapid rise
in cylinder pressure immediately following combustion creates mechanical
vibrations in the engine structure which are transmitted through the cylinder
walls, oil pan, rocker arm, and covers. Some of this vibration is subse-
quently radiated into the atmosphere as acoustic energy.
16
-------
Gasoline engines initiate combustion with a flame which spreads
smoothly throughout the cylinder until the fuel-air mixture is burned.
Diesel engines, however, rely on much higher compression ratios (about
17:1 rather than 9:1) to produce spontaneous combustion. This causes a
more rapid change in pressure in the cylinder, which in turn results in
increased engine vibration and hence higher noise levels than those
associated with gasoline engines. As a result, the mechanical noise
levels of diesel engines often are as much as 10 dB higher than those of
gasoline engines (22). The engine mechanical noise contribution in typical
/23\
diesel-powered trucks is on the order of 78 to 85 dB(Ar .
Turbochargers are often used to increase the pressure of the intake
air. This reduces the pressure fluctuations in the engine and, in turn,
lowers the engine noise lever '. However, turbochargers may in some
cases whine, contributing to the overall noise level.
Retrofit methods of reducing engine noise are generally one of two
kinds:
1. Modification of certain exterior surface covers.
2. Installation of acoustic absorption material and acoustic bar-
riers in the engine enclosure.
Engine noise reduction kits suitable for a limited number of engine models
are available from a few major engine manufacturers. These kits consist
of various acoustically treated panels and covers and provide a reduction
of about 3 dB in engine mechanical noise (as opposed to total vehicle noise
level) at a cost of $50 to $100 for materials* ^ and, typically, $30 for
installation' . Such kits are in limited production at this time and have
/O7\
not undergone complete durability testingv '.
AIR INDUCTION SYSTEM
Induction system noise is created by the opening and closing of the
intake valves; this action causes the volume of air in the system to
pulsate. The associated noise levels depend upon the type of engine, the
engine operating conditions, and whether it is turbocharged or naturally
aspirated. Typical intake noise levels alone vary from 70 to 80 dB(A)* '.
17
-------
The state of intake noise reduction technology is very similar to that
of exhaust noise reduction. Major manufacturers are able to provide
assistance in proper selection of air intake systems for all popular engine
models ^29*. Retrofitting the intake systems of trucks in service consists
of replacing older air cleaners with modern quality, dry element air cleam r
at an average cost of from $100 to $130* '. Intake cleaners and silencers
are manufactured largely by the major muffler manuf act'Tors.
TIRE/ROADWAY INTERACTION
Truck tires for highway usage can be classified into two categories
- rib tires and crossbar tires (also known as lug or cross rib tires). Rib
tires look like automobile tires, with the tread elements oriented circum-
ferentially around the tire. This is the most common type of truck tire and
can be used in all wheel positions. Rib tires are used almost exclusively on
steering axles because of their superior lateral traction and uniform wear
characteristics. Crossbar designs have the tread elements oriented trans-
versely to the plane of the tire. Many trucking companies prefer to use
crossbar tires on drive axles, since they provide up to 60% greater initial
(31)
tread depth1 ', and hence greater mileage before recapping.
The noise-generating mechanisms of tire/roadway interaction are not
completely understood. It is known that the entrapment and release of air
from the tire tread cavities produces noise. Also, it appears that the
132)
vibration of the tire contributes to the total noise lever '. However, the
effect on noise levels of the large lugs on crossbar tires and of the road
surface are not well quantified. The result is that basically all the noise
information available has been obtained experimentally, and tire manu-
facturers do not appear to be close to any major breakthrough that would
result in crossbar tire designs exhibiting significantly lower noise levels.
There seem to be no conclusive data which indicate any significant
difference in traction properties between rib and crossbar tires under dry,
wet, or icy conditions Any advantage in traction is probably in favor of
18
-------
rib tires, because they normally provide about 5% more rubber in contact
with the road. However, in snow, sand, gravel, mud, or loose dirt,
where the tire does not come into contact with a firm surface, some cross-
OS)
bars will give better traction than rib tiresv '.
Extensive measurements of the noise level produced by tires mounted
on the drive axle of a truck-tractor have been conducted by the National
f34)
Bureau of Standards and the Department of Transportation* ' (see Figure
4). Typical values of the noise level measured at 50 ft are 68 and 73 dB(A)
at 35 mph for new rib and crossbar tires, respectively, on a concrete
roadway. At 55 mph these levels typically increase to 75 and 83 dB(A/ ',
respectively, although higher values are by no means uncommon. In general,
rib tires produce lower noise levels than crossbar tires. The noise produced
increases with tire wear, reaching a maximum value when the tread is
approximately half worn. An increase in noise level of 5 dB(A) over the
/qcv
levels of new tires is not uncommon^ .
Data indicate that some retread tires having a tread composed largely
of pockets which are not vented either around the tire or to the side produce
excessive noise levels by allowing air to be trapped, compressed, and
subsequently released as the pockets pass through the footprint area of the
tire. These pocket retreads are responsible for noise levels around 95 dB(A)
at highway speeds * *.
COST OF RETROFITTING INDIVIDUAL TRUCKS
The noise control information given in the preceding section reflects
the state of available retrofit technology for each noise source. To reduce
the noise level produced by an existing vehicle, it is necessary to apply one
or more of the modifications outlined, depending upon the vehicle in question
and the overall noise reduction required. For example, more components
of an old, poorly maintained truck will normally need to be modified than
those of one in new condition. Also, more treatment will be required for
trucks originally built with very noisy diesel engines.
19
-------
50
60
Speed, KM/Hr
70 80
New Tires
Concrete
Loaded Vehicle
At 50 Feet
60
40 50
Speed, mph
Figure 4. Peak A-Weighted Sound Level, as Measured at 50
Feet, Versus Speed for a Loaded Single-Chassis
Vehicle Running on a Concrete Surface. Various
Types of New Tires are Represented on the Graph.
These Were Mounted on the Drive Axle(35)
20
-------
TECHNOLOGY AND COST REQUIRED TO COMPLY WITH A LOW-
SPEED STANDARD
Treatments indicative of what might be required to lower truck noise
(other than from tire/road interaction) to various levels and the associated
costs per treatment are listed in Table 4. The noise levels are for low-
speed full-throttle acceleration measured according to SAE J366a on an
open site over a hard surface. Since the noise levels of individual trucks
vary, not all trucks requiring treatment would require the treatments indi-
cated to meet each noise level. The percentage of trucks in Table 4 that
need each type of component change were estimated by an EPA contractor
from data gathered by a company located in a regulated region of the
country which has been extensively engaged in retrofitting trucks to reduce
their noise.
The estimated costs to achieve 90, 88 and 86 dB(A) are comparable to
the actual costs incurred by that company in retrofitting 7600 large multi-
axle trucks, which are shown in Table 5* '. The 7600 trucks include
both gasoline and diesel-powered units, representing the proportion of
each type that required retrofit or repair to meet the noise limits.
Very few trucks have actually been retrofitted to achieve a noise
level of 84 dB(A), since few State and local jurisdictions have low speed
noise standards at levels below 86 dB(A). The EPA contractor estimated
a range of costs of $292-462 to quiet the average multiaxle truck to 84
dB(A), while the retrofit service company estimated that it might cost
$950 to quiet a diesel multiaxle truck to that level. Costs should be some-
what lower for smaller medium and heavy duty trucks, some of which
could be quieted to 84 dB(A).
There is a practical limit as to what noise levels can be achieved on
all trucks through the use of retrofit technology. EPA studies have indi-
cated that it is not cost-effective and often not feasible to quiet in-service
motor vehicles much below the noise levels that characterized them when new.
There are trucks in the existing fleet that contain diesel engines that are
21
-------
TABLE 4
ESTIMATED COSTS TO RETROFIT TRUCKS TO VARIOUS NOISE
LEVELS (According to SAE J366a) IN 1973 DOLLARS
Noise Level Typical Estimated Cost % Trucks Exceeding .-wg. Co -t
dB(A) @ 50' Treatment Per Item $ Specified Noise Level Truck Hdrutu
Requiring Component
Change
90 Exhaust1 50-100
100%
$50-$100
Total $50-$100
88 Exhaust1 50-100
Fan2 35
100%
5%
50-100
2- 2
Total $52-$102
Exhaust3 100
86 Fan4 80
Intake5 115
100%
10%
5%
100
8
6
Total $114
1.
2.
3.
4.
5.
6.
7.
8.
Exhaust6 100-200
Fan7 285-400
84 Intake5 115
Engine8 80-130
Muffler and labor single or dual system
Replaced fan blade
100%
50%
25%
25%
Mean cost for muffler and labor, plus additional cost
requiring replacement of flexible tubing, etc.
Replaced fan blade and added shroud in some
Average cost of dry element air cleaner with
cases
built-in
Muffler and replacement of feasible pipessingle or
$100-$200
$143-$200t<
$ 29-$ 29
$ 20-$ 33
Total $292-$462
for some trucks
silencer
dual system
Viscous fan clutch and new fan blade in conjunction with shroud.
Thermostatically controlled clutch
Partial engine kit plus installation.
22
-------
TABLE 5
)FITTING \
SPECIFIED NOISE LEVELS ACCORDING TO SAE J366av
ACTUAL COSTS OF RETROFITTING 7600 TRUCKS TO ACHIEVE
,(38)
Level 90 dB(A) 88 dB(A) 86 dB(A) 84 dB(A)
Actual Cost (1973 $) $45-100 $50-110 $50-205 _
Per Truck
23
-------
too noisy to be sold in jurisdictions that enforce an 86 dB(A) noise emission
standard at 50 feet. These engines are being phased out of new trucks,
but they represent an obstacle to limits lower than 86 dB(A) for Interstate
Motor Carrier Regulations that must take best available technology and
cost of compliance into account.
Many heavy trucks are custom-built, and it is techno!ogica.ly pusaio
to replace engines or rebuild in-service trucks to achie\ _ large reduction
in noise emissions. However, this is not considered to be within the
definition of "best available technology," and would involve very high
costs. Even achieving 84 dB(A) for all trucks would require the extensive
use of engine enclosures that are not currently available and that have not
been adequately tested for safety and compatibility with engine maintenance
needs.
EPA believes that a noise level of 86 dB(A), measured according to
SAE J366a, is achievable through the use of best available technology by
almost all medium and heavy duty trucks in the existing fleet. It is also
achievable by buses, since they use the same engines and tires as trucks.
Trucks are already being retrofitted to reach 86 dB(A) in a number of
states and actual experience indicates that the associated costs were
$50-205 per truck in 1973 for those in-service trucks that had to be
retrofitted.
Additionally, at least one major truck manufacturer has indicated its
intention to work with suppliers to develop a retrofit noise control package
to bring older trucks into compliance with noise levels already proposed.
This should help provide the retrofit service capability that will be needed
to enable vehicles to comply with the Interstate Motor Carrier Regulations.
Table 4 indicates that most trucks currently exceeding 86 dB(A)
require only a muffler to be in compliance, and muffler manufacturers
have testified in public hearings that adequate mufflers can be available
in sufficient numbers to permit compliance of all trucks within one year
of promulgation of the Interstate Motor Carrier Regulations.
24
-------
TECHNOLOGY AND COST REQUIRED TO COMPLY WITH A HIGH-SPEED
STANDARD
Since engine-related noise does not increase at high speed above the levels
associated with low speed maximum acceleration, the high speed standard
should exceed the low speed standard only by the noise differential associated
with the increase in tire noise at higher speeds. Figure 4 indicated that tire
noise continues to increase as truck speed increases.
Considerable high speed noise reductions can be obtained through the
replacement of "pocket retread" tires by crossbar tires at no increase in cost
or loss of performance. However, crossbar tires begin to dominate overall
truck noise levels at speeds in excess of 45 mph and a high speed standard of
86 dB(A) might require the elimination of virtually all crossbar tires.
It appears that per-mile cost differentials between tires having different
types of tread may depend on tire composition and terrain as well as on motor
carrier recapping policies. A comprehensive study of cost-differentials
associated with the use of truck tires of different types is being carried out by
EPA as preparation for possible future tire regulations and/or revisions of the
Interstate Motor Carrier Regulations.
However, due to performance and safety requirements it does not appear
feasible or desirable to require the elimination of all crossbar tires at this
time. It may be desirable to further restrict the use of noisy crossbar tires
in the future, but such an action requires more data on cost, performance,
and safety differentials between tires of different treads than currently is
available.
Accordingly, a four decibel margin has been added to the 86 dB(A) low
speed standard to take tire noise into account. Actual experience indicates
that this will require the elimination of some crossbar tires on heavy trucks
that have a very large number of axles. However, it should still be possible
for these trucks to operate with crossbar tires on the drive axles.
A comparison of the results of surveys of actual truck noise levels (data
from the surveys is presented in section 4), indicates that essentially the
same percentages of trucks exceeded 86 dB(A) under low speed acceleration
25
-------
as exceeded 90 dB(A) under high speed conditions, and also that the per-
centages are very nearly the same for each MVMA class of trucks considered
separately by number of axles. This strongly suggests that the two standardr
are comparable.
For those trucks that must change from crossbar tires t-j rib t.!- i
order to comply with the standards, a small cost penalty may result. Ui'iei
a strategy of recapping each tire only once, the cost difierence between
crossbar and rib tires is approximately $. 23 per thousand miles. For a
single drive axle truck, this represents a cost difference of less than $. 001
per mile.
A high-speed noise level of 88 dB(A) would be achievable by two-axle
trucks because they have fewer tires than multiaxle trucks. A separate
standard was considered for this category, but an analysis of highway noise
levels performed using a DOT Highway Noise Prediction Model indicated that
reducing the noise emissions of a portion of the truck fleet over 10,000 pounds
by two decibels would have no measurable effect on highway noise levels.
Accordingly, one high-speed noise limit seemed reasonable for all motor
vehicles over 10,000 pounds GVWR operated by motor carriers engaged in
interstate commerce.
26
-------
Section 3
INTERSTATE MOTOR CARRIER REGULATIONS
This section contains a summary of the regulations, a short explanation
of the changes made in the regulations since the notice of proposed rule-
making, and an analysis of the relationship between the various test measure-
ment procedures used to ascertain compliance of motor vehicles with noise
emission standards.
SUMMARY OF THE REGULATIONS
The Interstate Motor Carrier Noise Emission Standards are applicable to
all motor vehicles above 10,000 Ib GVWR/GCWR operated by motor carriers
engaged in interstate commerce. There are two interrelated standards directed
to the way in which the motor vehicles are operated while in use. The first is
a requirement that motor vehicles generate no more than 86 dB(A) at 50 feet in
speed zones at or under 35 mph under all conditions. The second is that the
vehicles generate no more than 90 dB(A) at 50 feet in speed zones over 35 mph
under all conditions. The intent of these two standards is to limit maximum
propulsion system noise to the same,level in both speed zones, but to provide
an additional margin for tire noise in the high speed zones.
If the actual vehicle speed (rather than the posted speed limit) were used
in the regulation, then enforcement would recjuire the simultaneous measure-
ment of each vehicle's speed and noise level. This would be quite difficult in
the case of a truck operating in a stream of faster-moving passenger car
traffic. To remove this obstacle to enforcement, the standards are keyed to
the speed zone in which the vehicle is operating rather than its actual speed.
This is the rationale for setting the low-speed, high-speed break at 35 mph
rather than 45 mph, where tire noise could begin to be important.
A stationary engine run-up test standard of 88 dB(A) has been included in
order to permit enforcement at roadside weighing stations. This test will
27
-------
typically be performed over a hard site and is applicable only to vehicles with
engine speed governors. The test is inappropriate for vehicles without
governors because of the following:
a. Wide variability is introduced by operator technique and tachometer
errors in accelerating to maximum rated rpm in tests o
engines.
b. Wide variability exists in the maximum rated rpm Tui ungoverned
engines, and maximum rpm in a stationary run-up test may be fr i
above maximum rpm of the engine when in operation.
c. The possibility of catastrophic failure exists when an ungoverned
engine is accelerated rapidly to maximum speed when not under load.
Most vehicles will violate the regulations only when their exhaust systems
are faulty, and a visual exhaust system inspection standard has been included
to cover this possibility.
A visual tire inspection standard has also been included to provide an
effective means of eliminating the noisiest type of tire treat pattern, except
in cases where it can be shown that the vehicle can meet the 90 dB(A) standard
even when using tires whose tread appears to be noisy.
The effective date of the regulations is one year from the date of promul-
gation. EPA has determined that the required retrofit components will be
available within this period and that a one year effective date will not impose
an undue hardship on the trucking industry.
REVISION OF THE PROPOSED REGULATIONS PRIOR TO PROMULGATION
The Interstate Motor Carrier Noise Emission Regulations which are now
being promulgated incorporate several changes from the proposed regulations
which were published on July 27, 1973. These changes are based upon the
public comments received and upon the continuing study of motor carrier noise
by the Agency. In all but one instance such changes are not substantial; they
are only intended to further clarify the intent of the proposed regulations.
28
-------
The sole substantive change is the deletion of proposed Section 202.12,
"Standards for Level Street Operations 35 MPH or Under." This section was
originally proposed as it was felt that vehicles which could comply with a stan-
dard of 86 dB(A) under any conditions on highways with speed limits of 35 mph
or less could be driven so as to comply with a standard of 80 dB(A) when operated
at constant speed on level streets with speed limits of 35 mph or less. It was
the intent of the Agency through this section to thereby regulate the manner of
operation of the vehicle, by the driver, without imposing any additional noise
reduction requirement to the vehicle proper beyond that needed to meet the
86 dB(A) standard. Substantial questions were raised regarding the validity of
the data upon which the standard was based. The Agency, upon review of the
relevant data, lagrees with the comments and accordingly, the Standards for
Level Street Operations section has been deleted.
Those changes made to clarify the intent of the regulations, and the reasons
therefore, are as follows:
Section 202.10 - Definitions
"Common carrier by motor vehicle," "contract carrier by motor vehicle,"
and "private carrier of property by motor vehicle" were deleted. In their place,
the definition of "motor carrier" was expanded to incorporate, by reference,
the definition of those terms in paragraphs 14, 15, and 17, of Section 203 (a) of
the Interstate Commerce Act (49 USC 303 A). This treatment more closely
follows Section 18(d) of the Noise Control Act and thereby insures that any
question as to the definition of those terms will be resolved by reference to the
body of law which Congress intended to apply to Section 18.
The definitions of "dB(A),""sound pressure level, "and "sound level," were
changed slighty to be consistent with the definitions of those terms used in the
document "Information on Levels of Environmental Noise Requisite to Protect
Public Health and Welfare with an Adequate Margin of Safety," issued by the
Environmental Protection Agency in March 1974. "Fast meter response" has
been expanded for clarity.
29
-------
"Gross combination weight rating" (GCWR) has been added to avoid any
possible confusion over whether the regulation is applicable to combination
trucks (i.e., tractor-trailer rigs) over 10,000 pounds weight rating. The
provisions of Subpart B of the regulation are applicable to all single and com-
bination vehicles over 10,000 pounds GVWR or GCWR operated by interstate
motor carriers.
"Interstate commerce" has been modified to insure that any questions
as to its scope would be resolved by reference to Section 2G^a) of the Inter-
state Commerce Act, consistent with the reference to that Act in Section 18(d)
of the Noise Control Act.
"Person" has been deleted, since (as discussed below) that word is no
longer used in Subpart B of the regulations.
"Street," and "official traffic device," have been deleted, since pro-
posed Section 202.12 in which they were used has been deleted.
"Muffler" has been added to simplify the language of proposed Section
202.14, "Visual Exhaust System Inspection. "
"Open site" has been added to further clarify the standards.
Section 202.11 - Effective Date
An effective date of October 1, 1974 was originally proposed for the
regulations. The intent of the Agency in the Notice of Proposed Rulemaking
was that the proposed regulations would become effective one year from the
date of promulgation. This intent is retained in this new section.
Section 202.12 - Applicability
"Applicability" was moved to Subpart A of the final regulations as it is
appropriately considered a "general provision" of the regulations. It has
been modified to clarify the intent of the Agency that the standards do not
apply to noise emission from warning devices or auxiliary equipment mounted
on motor vehicles; and that compliance with any provision of Subpart B does
not excuse any motor vehicle from compliance with the other provisions of
Subpart B.
30
-------
Subpart B - Interstate Motor Carrier Operations
The language used in Subpart B has been changed from, "no person shall
operate," to "no motor carrier subject to these regulations shall operate...;"
and the language in section 202.20 was modified slightly to conform to this
change. This change is intended to reflect more accurately the intent of Congress
and these regulations, that they are to establish uniform national noise emission
regulations for those operations of interstate motor carriers which require such
treatment. The revised language clearly imposes sole responsibility for meeting
the requirements upon the motor carriers which own and operate the subject
motor vehicles. The proposed language, using the broad term "person," would
have imposed that responsibility upon the drivers of subject motor vehicles as
well as the companies which operate them. "Motor carrier," as defined in
these regulations, includes independent truckers who both own and drive their
own vehicles. The phrase "on an open site over any surface," was added to the
standards of Subpart B to further clarify the standards.
Section 202.21 - Standard for Operation Under Stationary Test
The language of this section has been modified to further clarify that it
applies only to vehicles which have an engine speed governor. Application of
a stationary run-up test to vehicles which are not equipped with engine speed
limiting devices could result in engine damage.
Section 202.22 - Visual Exhaust System Inspection
The intent of the Agency in requiring motor vehicles subject to this
regulation to be equipped with exhaust system noise dissipative devices has
been further clarified through modification of the language of proposed Section
202.14. In addition, the exception to the proposed requirement relating to
vehicles with gas driven turbochargers and equipped with engine brakes, which
were demonstrated to meet the other standards of Subpart B, has been deleted.
Such equipment is included in the term "other noise dissipative device," and
therefore need not be treated separately.
31
-------
Section 202.23 - Visual Tire Inspection
The intent of the Agency was to specifically preclude the use of "pocket
retread" tires which when new are demonstrably noisier without having any
accompanying benefit in safety or cost over other types of tires. The pro-
posed Section 202.15 has been modified in response to comments by tirr
manufacturers that the regulation as proposed could have covered some types
of tires which are not in fact exceptionally noisy.
Proposed Section 202.16 - Enforcement Procedures
This proposed section has been deleted. As the Noise Control Act
places enforcement responsibilities for these regulations with the Department
of Transportation, the section as proposed added nothing not specified in the
Act.
Proposed Subpart C - Special Local Conditions Determinations
The procedures for applying for determinations as called for in Section
18(c)(2) of the Act, will be published by EPA as "procedures" and not as part
of this regulation. Accordingly, Subpart C has been deleted.
Preemption
Under Subsection 18(c)(l) of the Noise Control Act, after the effective date
of these regulations no State or political subdivision thereof may adopt or enforce
any standard applicable to noise emissions resulting from the operation of motor
vehicles over 10,000 pounds GVWR or GCWR by motor carriers engaged in inter-
state commerce unless such standard is identical to the standard prescribed by
these regulations. Subsection 18(c)(2), however, provides that this section does
not diminish or enhance the rights of any State or political subdivision thereof
to establish and enforce standards or controls on levels of environmental noise,
or to control, license, regulate, or restrict the use, operation or movement of
any product if the Administrator, after consultation with the Secretary of Trans-
portation, determines that such standard, control, license, regulation, or restric-
tion is necessitated by special local conditions and is not in conflict with regula-
tions promulgated under Section 18.
32
-------
Conversely, Subsection 18(c)(l) does not in any way preempt State or
local standards applicable to noise emissions resulting from any operation
of interstate motor carriers which is not covered by Federal regulations.
Thus, under the proposed regulations States and localities will remain free
to enact and enforce noise regulations on motor carrier operations other than
their operation of motor vehicles over 10,000 pounds GVWR or GCWR, with-
out any special determination by the Administrator. Only after a Federal
regulation on noise emissions resulting from a particular interstate motor
carrier operation has become effective must the States and localities obtain
a special determination by the Administrator under Subsection 18(c)(2), in
order to adopt or enforce their own use restrictions or environmental noise
limits on that operation.
Some interstate motor carrier operations on which no Federal noise
standards or regulations have become effective, and which may, therefore,
be subjected to State and local noise standards without any special determina-
tion by the Administrator, may indirectly include motor vehicles which are
covered by preemptive Federal regulations. Motor carrier maintenance shops,
for example, may from time to time emit the noise of trucks undergoing tests
along with noises common to many industrial operations such as forging and
grinding; and motor carrier terminals and parking areas include trucks among
their many types of noise sources.
In most instances, compliance with State or local standards on non-
Federally regulated operations of motor carriers is achievable without affecting
the Federally regulated motor vehicles within them. Standards on noise
emissions from repair shops, for example, can be met by such measures as
improved sound insulation in the walls of the shop, buffer zones of land between
the shop and noise-impacted areas, and scheduling the operation of the shop to
reduce noise at those times of the day when its impact is most severe. Standards
on motor carrier terminals and parking areas can be met by a variety of steps,
including reducing the volume of loudspeaker systems by using a distributed sound
system or replacing speakers with two-way radios, reducing noise emissions
from equipment which is not covered by Federal regulations, installing noise
33
-------
barriers around noisy equipment, acquiring additional land to act as a noise
buffer, and locating noisy equipment such as parked trucks with operating
refrigeration equipment as far as possible from adjacent noise-sensitive property.
State or local regulations on noise emissions from motor carrier operations whijh
the motor carrier can reasonably meet by initiating measures such a u -
not standards applicable to noise emissions resulting from the o . V o . i
vehicles over 10,000 pounds GVWR or GCWR, and thus would nu I j preeni.
the proposed regulations. No special determination by the Administrator under
Subsection 18(c)(2) would be necessary. State or local noise standards on ope*-
tions involved in interstate commerce such as motor carrier terminals are,
course, subject to Constitutional prohibition if they are so stringent as to plat i ar
undue burden on interstate commerce.
In some cases, however, a State or local noise regulation which is not stated
as a regulation applicable to a Federally regulated operation may be such a regu-
lation in effect, if the only way the regulation could be met would be to modify the
equipment which meets the Federal regulation applicable to it. This would be the
case, for example, if after the proposed regulations become effective, a State or
locality attempted to adopt or enforce a limit on noise emissions from motor
carrier terminals in urban areas which could not reasonably be met by measures
such as noise barriers or relocating the motor vehicles to which this regulation
is applicable. Such regulation would, in effect, require modifications to motor
vehicles even though they met the Federal regulations and would thus be a regu-
lation applicable to them which would be preempted under Subsection 18(c)(l). It
could not stand if it differed from the Federal regulations, unless the Administrator
made the determinations specified in Subsection 18(c)(2). The same would be true
of any State or local standard on motor carrier operations which could not reasonably
be met except by modifying motor vehicles which comply with the proposed Federal
standards.
State and local regulations on motor carrier operations which are not directed
at the control of noise, or which include noise control as only one of many purposes
such as safety, traffic control, and the like, are not preempted by Subsection 18(c)(l)
of the Noise Control Act and require no special determination under Subsection 18(c)(2)
34
-------
to be adopted or enforced. Thus, the designation of some streets as truck routes,
and prohibition of trucks from other streets, by State or local governments, are
valid without any special determination under Subsection 18(c)(2).
Auxiliary Equipment Considerations
Some types of auxiliary equipment used in vehicles operated by interstate motor
carriers are necessary for the comfort or safety of passengers, or for the preser-
vation of cargo. Principal examples of such auxiliary equipment are refrigeration
or air conditioning units and concrete mixer bodies and drives. The auxiliary equip-
ment noise emissions for these two types of vehicles, in particular, are at a level
far enough below other significant components of vehicle noise, as EPA's data
indicate, to be masked by other noise sources during normal vehicle highway
operations.
Other auxiliary equipment, however, normally operates only when the trans-
porting vehicle is stationary or moving at a very slow speed, normally less than 5
mph. Examples of such equipment include cranes, asphalt spreaders, ditch diggers,
liquid or slurry pumps, air compressors, welders, and trash compactors. The
operation of such equipment is not intended to be covered by these regulations.
Emergency Equipment and Vehicles
Because of the emergency or safety aspects of their operation the regulations
are not applicable to vehicles such as fire engines, ambulances, police vans, and
rescue vans when responding to emergency calls. Similarly, these regulations
are not intended to apply to snow plow operations.
Enforcement Procedures, Violations, and Penalties
Enforcement procedures are to be developed and promulgated under separate
rule making by the Department of Transportation. Such enforcement procedures
will specify minimum requirements for instrumentation, test sites, and other
conditions necessary to insure uniformity in testing and a minimum level of
precision.
Enforcement of the standards is contemplated to be more efficient under
some conditions if measurements are permitted to be made at distances other
than 50 feet under procedures that provide for equivalency to the standards
measured at 50 feet.
35
-------
Section 10 of the Act specifies that any violation of these and any future
regulations established under the,authority of section 18 of the Act constitutes
a prohibited act. Any person who willfully or knowingly violates the regulation
shall be punished by a fine of not more than $25,000.00 per day of violate *M*
imprisonment for not more than one year, or by both, or a. fin" r.s\. * - cc
$50,000.00 per day of violation, or imprisonment for not more tlidn two yean
or by both, following a conviction for a previous violation ot the Noise Control
Act.
RELATIONSHIP BETWEEN LOW-SPEED MEASUREMENT PROCEDURES
During the Public Hearings on Noise Abatement and Control held in San
Francisco in September 1971, testimony was offered to show the variations in
noise level of a truck as measured under maximum acceleration low-speed
conditions at nine different sites. Compared to a hard surface open site, grass-
covered sites produced noise levels that were 1.5 to 2.0 dB(A) lower, while the
presence of near-by buildings produced noise levels 1.5 to 2.0 dB(A) higher.
This implies that a truck in compliance with a standard as measured over a
soft surface could be out of compliance as measured over a hard surface unless
suitable correction factors are applied.
In actual practice, highway measurement and enforcement of the noise emis-
sion standards contained in these regulations will occur on sites having surfaces
that range from hard to soft. Motor vehicles covered by the regulations should
have no trouble being retrofitted to comply with an 86 dBA standard as measured
at a typical roadsite site.
This same rationale has been used to set the level of 88 dB(A) for the Sta-
tionary Run-up Test Standard. The stationary run-up test (SRUT) is a means
of determining maximum propulsion system noise. A vehicle propulsion system
which emits a given sound power by this test will typically emit that same value
in use when power requirements are maximum due to conditions of load, accelera-
tion, and grade when measurement site parameters are comparable.
The stationary standard at 88 dB(A) is approximately equivalent to the low
speed standard at 86 dB(A) because of the different measurement uites used.
Both levels would be the same if both were to be implemented on pavement, or
36
-------
both on grassy sites. This level would also be the same if the J366 maximum
noise test were included in the standards. In a tabular form the relationship
between the three test methods is as follows:
Stationary Max-Noise Low
Runup Speed Passby J366
Hard Site 88 88 88
Soft Site 86 86 86
SRUT was developed because the Society of Automotive Engineers J366a
test, which is almost universally performed by vehicle manufacturers, their
customers, and their suppliers, is wholly unsuitable for use in roadside
enforcement of a motor carrier regulation because of its technical require-
ments.
In order to obtain information on the feasibility of using SRUT as an
enforcement test procedure, tests were performed at the International Harvester
Company Truck Engineering Center at the request of EPA. Although the data
collected do not represent a sample large enough to have statistical significance,
the experiment is indicative of what relationship can be expected between SAE
J366a, SRUT, and Maximum Acceleration Passby results as measured over a
hard surface. The data are presented in Figures 5, 6, and 7 and Table 5.
37
-------
90
dBA
CO
oo
80
70
90
.3 dBA
dBA
80
70
86.8 dBA
r~
I I
SECONDS
SECONDS
J366a: TRACTOR ONLY
STATIONARY RUNUP TEST
Figure 5. Noise Level of a Large Diesel Truck as it
Approaches and Passes a Microphone in
the J366a Test.
Figure 6. Noise Level cr "he Same Truck as
it Idles, Folio . d L>y Engine Accel-
eration to M^xin. in Governed rpm
inib^ 'tati'M ji-up Test.
-------
CO
CO
dBA
90
80
70
60
86.3 dBA
I I
SECONDS
MAXIMUM ACCELERATION TEST: TRACTOR PLUS TRAILER (GCW = 72,600 Ib)
Figure 7. Noise Level from the Same Tractor while Pulling a Load as it Accelerates Past a Microphone
in a Pass-by Test.
-------
Table 5
MEASURED VALUES OF NOISE LEVEL IN dB(A) OF SEVERAL TESTS
ON TWO DIFFERENT TYPES OF TRUCKS.
PASSBY MICROPHONE LOCATIONS ARE ALL 50 FT FROM THE LINE OF
TRAVEL, EACH 50 FT SUCCESSIVELY FARTHER
FROM THE START POSITION.
72,600 LB DIESEL 56,000 LB DIESEL
TEST CAB-OVER-ENGINE CONVENTIONAL CAB
LEFTSIDE RIGHTSIDE LEFTSIDE RIGHTSIDE
J366a (Tractor only) 86.4 dB(A) 86.3 dB(A) 87.3 dB(A) 87.0 dB{A)
SRUT 86.4 86.8 87.0 89.2
Acceleration Passby
Location #1 87.0 86.3 87.5 88.0
Location #2 86.3 87.0 85.9 87.5
Location #3 85.4 85.8 86.3 88.0
Location #4 86.0 86.8 85.5 87.2
Two large diesel trucks were used for the tests, and in performing these
tests all measurement conditions were identical: paved surface, microphone
located 4 ft high, 50 ft from the source. The same series of tests, if performed
at a different site, would be expected to produce results differing in proportion
to the acoustic reflectivity of the surface between microphone and test vehicle
and due to normal variations in the tests themselves which render them less
than exactly repeatable.
This example shows essentially the same maximum noise level for all tests.
However, identical results are not always achievable under such comparisons;
the statistical correlation between J366a and SRUT is discussed below. Maximum
noise measured during acceleration will vary to some extent as a result of the
chance location of the microphone in relation to the maximum noise point in the
vehicle gearshift cycle.
40
-------
77 78 79 80 81 82 83 84 85. 86 87-
J-366a
dB(A)
89 90 91 92 93 94 95 96
87
86
85
84
83
82
Correlation Between
81 J 366a & Stationary Test
80
79 =<
79
78
77
CO
Figure 8. Plot of Test Results According to SRUT and SAE J366a for 877
Trucks.
-------
STATIONARY RUN-UP TEST CORRELATION WITH SAE J366a
A very substantial data base has recently become available that relates the
measurements of truck noise taken using the SAE J366a maximum acceleration
pass-by test and the stationary Runup Test (SRUT). The data has been collected ard
compiled by the Society of Automotive Engineers from several industrial sorrofi-
The stationary run-up test consists of measuring the maximum A -v :: iic
sound level at a distance of 50 feet from the vehicle engine exhaust during
maximum acceleration of the engine from low idle to high idle. The test is
conducted with the transmission in neutral and the clutch engaged. The inertia]
load of the engine during rapid engine speed acceleration makes an external
load on the engine unnecessary. SRUT site and sound measurement instrumen-
tation requirements are similar to the SAE - J366a requirements. Most truck
weigh stations can meet these site requirements.
The stationary run-up test will be quite useful for enforcement at State
inspection stations and weigh stations. A fleet owner may also use the test
to check his vehicle for compliance. The correlation of the stationary run-up
test with SAE-J366a is very good. Over 800 different trucks with governed
engines have been tested per SAE-J366a and per the stationary run-up test
procedure. The results of these tests are plotted in Figure 8. To better
understand the meaning of the data points in Figure 8, a statistical analysis
of this information is presented in Figure 9.
The analysis shows that given comparable site conditions the SAE J366a
test yields noise level measurements that are about 0.5 decibels higher on the
average for a given truck than the stationary run-up test measurements. The
standard deviation of the difference between the two measurements was 1.4 dB(A)
for the trucks in the sample. This means that for 95% of the 877 trucks tested,
the stationary run-up test measurement did not exceed the SAE J366a measure-
ment by more than 2 dB(A).
The correlation coefficient for the two sets of test results was computed
for a sub-sample of 210 of these trucks, and was found to be 0.71 (where 1.0
represents perfect correlation). The fact that the correlation was so high indi-
cates that a stationary run-up test can be used as a good approximati n to a low
speed acceleration test.
42
-------
70
60
50
8 40
o
0)
0)
JQ
30
In
20
10
-5 -4 -3 -2 -1
+1 +2 +3 +4 +5
(Stationary Runup Test)-(SAE J336a) dB
Figure 9. (Stationary Run-up Test) - (SAE J366a), dB
43
-------
Section 4
NOISE MEASUREMENT OF IN-SERVICE VEHICLES
This section presents the results and implications of a r i-"'>er of surveys
of the noise produced by motor vehicles of different kinds, measured at differenl
speeds and conditions according to several standard test procedures.
Light trucks - those with a gross vehicle weight rating (GVWR) of 10,00,0 Ib.
or less - typically produce peak passby noise levels of 64 to 72 dB(A) at 35 mph
when measured at 50 ft. These noise levels are about the same as those pro-
duced by passenger cars at the same speed (40). This result is not surprising,
since the major noise-producing components of light trucks are very similar to
those of automobiles: both are powered by similar gasoline engines, both have
two-axle chassis, and both usually use similar rib-type tires.
Heavy and Medium Duty Vehicles (those with a GVWR or gross combination
weight rating (GCWR) of more than 10,000 Ib.) can produce peak passby noise
levels of 95 dB(A) or more at 50 ft. (41).
Although all vehicles contribute to the noise emitted along streets and high-
ways (which determines the ambient noise level in most urban communities (42)),
Heavy and Medium Duty trucks cause a noise problem that can be separated from
the problem of motor vehicle noise in general. Heavy trucks emit noise levels
that are so much higher than those of other motor vehicles that they stand out
very noticeably. Noise peaks of 12 dB above the ambient noise level from other
traffic are commonly observed when a heavy truck passes by (43).
MEASUREMENT METHODOLOGY
Noise is measured by determining (by means of a sound level meter) the
magnitude of pressure variations of various frequencies in the air. Since a
person's subjective estimate of the magnitude of a sound is dependent upon the
relative magnitude of its component frequencies, a weighting network is usually
employed to match the response of the sound level meter to that of the human
44
-------
ear (44). The most commonly used network is the A-weighting network, which
is contained in all sound level meters. Noise levels measured on the A-weighted
noise scale are recorded using the notation dB(A). Noise scales other than A, B,
and C are available, but they require a more complex analysis procedure, which
is normally not justified by improved correlation with human assessment (45).
Because noise levels can peak rapidly as a truck passes by, the sound level meter
is usually set to "fast" response.
It has been argued that the A-weighted sound level discriminates against
low frequencies and, consequently, should be replaced by the C-weighted sound
level in motor carrier noise standards. However, the ear also discriminates
against low frequencies so that at low frequencies the sound pressure level must
be comparatively high before it can even be heard. This may explain why the
correlations between A-weighted sound level and human response are consistently
better than that obtained with the C-weighted sound level.
A-weighting has been shown to be a fairly good and consistent indicator of
loudness for a variety of common noises (46, 47). On the other hand, the C-
weighted level is consistently and significantly poorer than the A-weighted level
(48). Insofar as a predictor for speech interference for a variety of noises, the
C-weighted level is very poor as compared to A-weighted level (49). It may be
concluded from the literature that of all standardized weightings, the A-weighted
sound level has been the most successful of these measures as an indicator of
human response. Some improvements could probably be gained by the new
weighting characteristics that have been suggested recently (N, D, Dl, and D2);
however, these have not been nationally or internationally agreed upon; thus, no
standardized procedures or equipment exist for them at the present time.
Noise levels decrease with distance from the noise source, so it is important
to specify the distance at which measurements are to be made. For measuring
truck noise, the most usual measurement distance selected is 50 ft. At closer
distances, slight variations in measurement distance can produce significant
errors in the measured noise level (50); at greater distances, background noise
levels and the presence of noise-reflecting surfaces can pose problems in site
selection (51).
45
-------
In the surveys presented in this section, an effort was made to maintain
standard conditions at almost all sites. Suitable instrumentation was used;
sound level meters met the requirements of ANSI SI. 4-1971, American
National Standard Specification for Sound Level Meters. Microphone calibra-
tion was performed by an appropriate procedure and at prescribed intervale
An anemometer was used to determine wind velocity, and microphone ; wej.
equipped with suitable wind screens.
Restrictions were made to prevent measurements during unfavorable
weather conditions (e. g., wind and precipitation). The standard site for pass-
by measurements was an open space free of sound reflecting objects such as
barriers, walls, hills, parked vehicles, and signs. The nearest reflector to
the microphone or vehicle was more than 80 feet away. The road surface was
paved, and the ground between the roadside and the microphone was covered by
short grass in most cases.
The standard site for the stationary runup test included space requirements
that were the same as for pass-by measurements, and the surface between the
microphone and vehicle was paved. Microphones for stationary and pass-by
measurements were located 50 feet from the centerline of the vehicle or lane
of travel, 4 feet off the ground, and oriented as per manufacturer's instructions.
Variations from the standard measurement sites and microphone locations were
allowed if the measurements were suitably adjusted to be equivalent to measure-
ments made via the standard methods. Exact procedures for the tests are included
in the appendix.
SURVEYS OF TRUCK NOISE
Truck noise surveys have been conducted in California in 1965 (52), and 1971
(53), in the State of Washington in 1972 (54), and in New Jersey in 1972 (55). In
1973, EPA contractors conducted additional truck noise surveys of 6,875 trucks
operating at speeds over 35 MPH in the states of California, Colorado, Illinois,
Kentucky, Maryland, New Jersey, New York, Pennsylvania, and Texas, and of
2,583 trucks operating under acceleration conditions at speeds under 35 MPH
in the states of California, Colorado, Florida, Maryland, Missouri, Texas,
and Virginia.
46
-------
In almost all cases, measurements were made at a distance of 50 ft from
the center of the first (outer) lane of travel, using A-weighting and fast response
on the sound level meter. In the 1973 surveys, the type of truck and number of
axles were recorded in order to permit detailed analyses of the noise level dis-
tributions for various types of trucks.
In addition, a study of noise levels of 60 trucks produced during a stationary
run-up test was carried out by EPA in Virginia in February, 1974.
ANALYSES OF HIGH SPEED (OVER 35 MPH) SURVEY DATA
Figure 10 shows cumulative probability distributions for the peak passby
noise levels measured at 50 ft under high-speed freeway conditions in the surveys
conducted prior to 1973. The data shown are for heavy trucks: 5,838 diesel trucks
in California in 1965 (56), 172 combination trucks in California in 1971 (57), 531
trucks with 3 or more axles in Washington in 1972 (58), and 1,000 trucks with 3
or more axles in New Jersey in 1972 (59). The data are in close agreement: typi-
cally, 50% of the trucks were observed to exceed 87 to 88 dB(A) and 20% were
observed to exceed 90 dB(A).
Figure 11 shows that under high-speed freeway conditions, buses are about
2 dB quieter than heavy trucks. Approximately 50% exceed 85 dB(A), and 6%
exceed 90 dB(A). These data were obtained in New Jersey in 1973.
Table 6 shows the mean noise levels and percentages of all trucks with six
or more wheels that were observed to exceed 90.0 dB(A) under high-speed free-
way conditions in ten states. These data were all obtained in 1973, except for
the Washington state data, which were obtained in 1972. The arithmetic mean
of the percentage of trucks exceeding 90.0 dB(A) is 23.1%. When the data is
weighted by the sample size obtained in each state, this percentage drops to 22.6%.
When the data are weighted by the number of registered trucks above 10,000 Ib
GVWR/GCWR, the percentage drops to 21.0%.
47
-------
99.0
OQ D
yy.o
QQ C,
no
yy
98
95
90
80
70
o 60
ra
o 50
.£ 40
v»
"^ 30
0)
B 20
3?
10
5
2
1.0
0.5
0.2
0.1
0.05
0.01
(^
\ >
V
V V
0
S
s^;-
^
Data
OCa
Ca
Av/u-
Wo
S
S
vS
\\
\
Source
ifornia (1971) 172 Combination Vehicle;
ifornia (1965) 5.838 Diesel Trucks
shington (1972) 531 Trucks,
3 or More Axles
w Jersey (1972) 1000 Trucks
3 or More Axles
^y
^\v
N V^\
S
|
^\
X
V
o
^A
VN£\
No \
m^^m
^A
\ "
\
S
^
80 82 84 86 88 90 92
Enforcement Limit, dB(A) at 50 Ft
Figure 10. Enforcement Limit, dB(A) At 50 Ft
94
96
98
100
48
-------
"oi
s
-1
ffi
V)
99.9
99.8
99.5
, 99
I 98
95
90
a
5 80
01
o 70
o
<
Z
0)
60
50
40
30
20
ra
£ 10
-------
Table 6
ALL TRUCKS ABOVE 10,000 LBS GVWR OR GCWR
State
CA
CO
IL
KY
MD
NJ
NY
PA
TX
WA
Source
W.L.
BBN
BBN
BBN
Md.DOT
BBN
BBN
W.L.
BBN
WA-72
Mean Noise
Level
85.4dB(A) (a)
84.6
89.1
88.8
88.1
87.2
88.8
86. 2 (a)
83.7
86. 6 (a)
Mean Speed
51. 7mph
57.2
61.3
-
56.5
60.0
-
56.1
-
% Above
90. 0 dB(A)
5.0%
10.0
42.0
40.0
30.0
20.0
43.0
13.0
12.5
16.0
mean percentage exceeding given noise level:
23.1%
(a) median
50
-------
Table 7 shows the same results by type of truck for the nine states in
which data were obtained in 1973. The mean percentages of trucks exceeding
90.0 dB(A) ranges from 1.9% of 2-axle trucks to 36.1% of 5-axle trucks.
A crucial distinction must now be made. The fact that approximately 23%
of all trucks observed in these surveys exceeded 90.0 dB(A) does not mean
that 23% of all registered trucks above 10,000 Ib GVWR/GCWR will exceed this
level. This is because larger trucks operate many more miles per vehicle per
year than smaller trucks do and accordingly show up more frequently in surveys
than their actual numbers would indicate. For example, 2-axle trucks average
10,600 vehicle miles per year, while 5-axle trucks average 63,000 vehicle miles
per year (60).
Using data from the 1972 Census of Transportation - Truck Inventory and
Use Survey (61), the following breakdown was obtained for the population of
registered trucks above 10,000 Ib GVWR/GCWR.
TRUCK POPULATION OVER 10,000 POUNDS GVWR/GCWR
2-axle straight truck 71.7%
3-axle straight truck 10.6%
3-axle combination truck 2.4%
4-axle combination truck 5.3%
5-axle combination truck 8.1%
Not reported or other 1.9%
100.0%
Table 8 shows that when these percentages are multiplied by the mean per-
centages of each type exceeding 90.0 dB(A) from Table 7, a total of about 7% of
all registered trucks above 10,000 Ib GVWR/GCWR exceed 90.0 dB(A) at freeway
speeds.
51
-------
Table 7
2 AXLE STRAIGHT TRUCK ABOVE 10,000 LBS GVWR
State
CA
CO
IL
KY
MD
NJ
NY
PA
TX
Source
W.L.
BBN
BBN
BBN
Md.DOT
BBN
BBN
W.L.
BBN
Mean Noise
Level
81.0dB(A) (a)
80.4
83.1
82.9
83.9
82.3
85.1
81. 2 (a)
78.6
Mean Speed
-
50. 9mph
55.7
57.7
-
55.7
59.4
-
54.6
% Above
90. 0 dB(A)
1.2%
1.3
1.0
1.0
3.5
0.6
6.0
0.9
0.6
mean percentage exceeding given
noise level: 1.9%
3 AXLE STRAIGHT TRUCK
CA
CO
IL
KY
MD
NJ
NY
PA
TX
W.L.
BBN
BBN
BBN
Md. DOT
BBN
W.L.
W.L.
BBN
85. 2 (a) (b)
84.1
85.8
87.7
87.5
84.7
88. 0 (a) (b)
84. 5 (a) (b)
84.8
-
47.7
54.5
59.9
-
57.4
-
-
50.6
8.0
1.2
9.0
*
*
*
26.0
2.0
*
mean percentage exceeding given
noise level: 9.3%
(a) median
(b) all 3 axle trucks
* insufficient data
52
-------
Table 7 (Continued)
3 AXLE COMBINATION TRUCK
State
CA
CO
IL
KY
MD
NJ
NY
PA
TX
Source
W.L.
BBN
BBN
BBN
Md. DOT
BBN
W.L.
W.L.
BBN
Mean Noise
Level
85. 2 (a) (b)
83.8
86.0
87.8
86.6
85.7
88. 0 (a) (b)
84. 5 (a) (b)
83.0
Mean Speed
-
51.9
55.7
59.0
-
57.2
-
-
56.5
% Above
90. 0 dB(A)
8.0%
*
*
*
17.0
1.0
26.0
2.0
*
mean percentage exceeding given
noise level: 10.8%
4 AXLE COMBINATION TRUCK
CA
CO
IL
KY
MD
NJ
NY
PA
TX
W.L.
BBN
BBN
BBN
Md.DOT
BBN
BBN
W.L.
BBN
84. 2 (a)
84.8
87.1
88.0
87.9
86.7
88.8
85. 7 (a)
83.9
-
49.0
55.4
61.0
-
57.7
58.8
-
56.4
3.0
9.0
22.0
24.0
26.0
11.0
26.0
9.0
4.5
mean percentage exceeding given
noise level: 15.0%
(a) median
(b) all 3 axle trucks
* insufficient data
53
-------
Table 7 (Continued)
5 AXLE COMBINATION TRUCK
State
CA
CO
IL
KY
MD
NJ
NY
PA
TX
Source
W.L.
BBN
BBN
BBN
Md. DOT
BBN
BBN
W.L.
BBN
Mean Noise
Level
85. 9 (a)
87.0
90.2
90.6
89.7
88.3
91.2
87. 6 (a)
87.5
Mean Speed
53.7
57.7
62.6
-
58.7
61.6
-
57.9
% Above
90.0 dB(A)
7.0%
j> J
51.0
56.0
42.0
32.0
74.0
22.0
23.0
mean percentage exceeding given
noise level: 36.1%
(a) median
54
-------
Table 8
TRUCKS EXCEEDING 90. 0 dBA AT SPEEDS OVER 35 MPH
2 axle straight truck
3 axle straight truck
3 axle combination
4 axle combination
5 axle combination
All other (b)
% of all
trucks above
lO.OOOlbs (a)
71.7%
10.6
2.4
5.3
8.1
1.9
100. 7%
% of type
exceeding
90. 0 dB(A)
1.9%
9.3
10.8
15.0
36.1
36. 1 (c)
% of all trucks
above 10, 000 Ibs
affected (a)
1.4%
1.0
0.3
0.8
2.9
0.7
7.1%
(a) Estimates are for all trucks over 10,000 pounds GVWR or GCWR,
including trucks not involved in interstate commerce.
(b) "All other" includes straight truck with trailer, combinations with
6 or more axles, and combinations not specified in the 1972 Census
of Transportation survey.
(c) No data available. Percentage exceeding noise level is assumed to
be the same as for 5 axle combinations.
55
-------
ANALYSIS OF LOW SPEED (UNDER 35 MPH) SURVEY DATA
Table 9 shows the percentages of trucks above 10,000 Ibs GVWR/GCWR
that exceeded 86 dB(A) under low speed acceleration conditions in various states.
These data were collected at roadside sites in seven states with acoustic charac-
teristics similar to those of the sites used for the collection of 1 c;t sj.ee'' a. a,
except in Maryland and Virginia. At these two sites, the paved ' urfr < - co sereA
the entire distance between the roadway and the microphone, a . -here was no
grassy shoulder area. A site correction factor of -1.5 dB has been assumed for
the data obtained at these sites in order to permit direct comparison with the
other data, most of which was taken at open sites over a "soft" surface.
A comparison of the results shown in Table 9 with those of Tables 6 and 7
demonstrates not only that similar total percentages of trucks were observed
to exceed 86 dB(A) under low speed acceleration as exceeded 90 dB(A) under high
speed conditions, but also that these percentages are very nearly the same for
each class of trucks considered separately. For example, 2% of all 2-axle trucks
exceeded 86 dB(A) under low speed acceleration, while 1.9% exceeded 90 dB(A)
under high speed freeway conditions. For 4-axle trucks, the results are 21%
and 15%, respectively. In this sense, an 86 dB(A) limit under low speed condi-
tions can be considered to be about as stringent as a 90 dB(A) high speed limit.
The calculations in Table 10 yield an estimate that at the present time about
8% of the nationwide truck fleet over 10,000 pounds exceeds 86 dBA during low-
speed acceleration measured at an open site over a soft surface.
ANALYSIS OF STATIONARY RUNUP TEST DATA
EPA conducted a small-scale investigation to determine that the Stationary
Runup Test (SHUT) is suitable with respect to practical enforcement, particu-
larly in terms of repeatability, and to check that predicted violation rates as
enforced would be consistent with those of the low-speed passby test. A state-
weighing station in Virginia cooperated by allowing a survey team to request the
participation of drivers as they appeared for weighing their trucks. Sixty
trucks were measured by the method outlined in the appendix.
56
-------
Table 9
PERCENTAGE OF TRUCKS AT OR ABOVE 86 dB(A)
DURING ACCELERATION BELOW 35 MPH
State
California
Colorado
Florida
Maryland (a)
Missouri
Texas
Virginia (a)
Mean
Excluding
California
* insufficient data
(a). -1.5 dB site correction factor assumed (see text)
2-Axle
2%
3
1
*
0
2
*
2%
3-Axle
12%
6
7
11
28
13
11
13%
4-Axle
*
27
13
20
27
*
20
21%
5-Axle
20%
24
36
40
49
26
42
36%
All Trucks
10%
17
10
35
39
17
40
24%
57
-------
Table 10
PERCENT OF TRUCKS OVER 10,000 POUNDS
EXCEEDING 86 dB(A) UNDER 35 MPH
% of Trucks Above % of Type Ex- % of Trucks Above
No. of Axles 10. OOP pounds (a) ceedlng 86 dB(A) 10. OOP pounds Affected
2 axle
3 axle
4 axle
5 axle
All other (b)
72%
13
5
8
2
100%
2%
13
21
36
36 (c)
1.4*
1.7
1.3
2.9
0.7
7.8%
a) Estimates are for all trucks over 10,000 pounds GVWR or GCWR,
including trucks not involved in interstate commerce.
b) "All other" includes straight truck with trailer, combinations with 6
or more axles, and combinations not specified in the 1972 Census of
Transportation survey.
c) No data available. Percentage exceeding noise level is assumed to be
the same as for 5 axle trucks. .
58
-------
A representative from the Bureau of Motor Carrier Safety explained to
each driver the technique required to achieve a maximum engine runup. Four
runups were performed for each truck and the noise level measurements were
recorded. In many cases, the first attempt by the driver did not produce the
rapid engine acceleration necessary for the test. However, in most cases the
test was performed properly in subsequent attempts.
The average of the three highest noise levels obtained from the four tests
was used to characterize the SHUT level for comparison with the EPA standard
level of 88 dB(A). The consistency of the three highest levels was such that
for 93% of the trucks tested, the range of noise levels was 1.5 dB(A) or less.
Of the small population tested 35% exceeded the noise level standard of 88 dB(A).
CLASSIFICATION OF TRUCKS INTO CATEGORIES
The studies performed indicate that truck mean noise levels increase with
vehicle size (or number of axles) and speed. Accordingly, regulations have been
promulgated for high and low speed truck operations in order to quiet both engine-
related noise and tire noise. An effort was also made to develop a suitable classi-
fication for trucks based on weight or number of axles in order to require the use
of best available technology in trucks of all sizes.
Figure 12 presents cumulative distributions of peak pass-by noise levels
over 35 MPH at 50 feet for trucks by number of axles. These data were obtained
in New Jersey in 1973, but the differences observed between different vehicle
classes are typical of other states as well. Mean noise levels for 2-axle, 3-
axle, 4-axle, and 5-axle trucks are 82, 86, 87, and 89 dB(A), respectively.
The greatest difference in means occurs between 2 and 3-axle trucks. Since
this is also the break point between medium and heavy duty trucks, the
Agency examined the feasibility of classifying trucks over 10,000 pounds into
two categories in order to promulgate stricter regulations for smaller vehicles.
Although there is a significant difference between the mean noise levels
of medium and heavy duty trucks, there is considerable overlap in the
distributions of noise levels of trucks of different sizes currently on the
road. The basic problem is that noisy propulsion systems are not confined
to heavy duty trucks. Many truck manufacturers offer and have traditionally
sold the same engines in trucks having 2 or 3 axles. For example,
59
-------
99.9
99.8
99.5
99
98
95
90
c
OJ
> 80
70
o
<
60
50
40
y 30
c
OJ
> 20
10
aj
CL
1.0
0.5
0.2
0.1
IZ^~
- ^
- 1
\
\
\
1
\
v
\
\
\
\
\
\
\
1
*
*
\
,
\ \
\
\
\ \
\
\
\
\
\
\
1
*
\°'-
-.
\\
s \
\ V '
\ \
v\
w \
Passenger Cars
(Data Collected
in Baltimrirp)
2-Axle
(Six Wh
__._ 4-Axle
Trucks
eels)
Trucks
Trucks
>
\
>
^
.
*
L *,
. \ \
\ \ '
\ \
v \ \
\\
V
'\
V ^-i
\
\
1
' -
~~
1 ^~
|
60
70
72 74 76 78 80 82 84 86 88 90
Peak Passby Noise Level, dB(A) at 50 ft
92
94
96
98 100
Figure 12.
Cumulative Distribution of Peak Passby Noise Levels for Various Classes of Trucks .it Speeds
Over 35 MPH.
-------
according to MVMA data, 3.5% of all new medium duty trucks sold in 1972 were
powered by diesel engines similar or identical to those engines used on heavy
duty trucks. The same situation has characterized the use of noisy gasoline
engines. For this reason, further classification of motor vehicles into
categories over 10,000 pounds GVWR is not feasible for the low speed standard.
An analysis of the feasibility of classifying trucks at speeds over 35 MPH
indicated that 88 dBA could probably be achieved by 2-axle vehicles, since they
use fewer tires than multi-axle combination vehicles. However, the analysis of
the environmental impact of the high speed standard indicated that highway noise
levels are determined almost entirely by the noise levels of the heaviest trucks
(those with 4 and 5 axles}. The additional assumption of an 88 dB(A) limit on
2-axle trucks above 10,000 Ibs GVWR and an 82 dB(A) limit on all passenger
cars and light trucks in addition to the proposed standards in the analysis pro-
duced essentially no further decrease in highway noise levels.
The Agency considered limiting the coverage of the Interstate Motor Carrier
Regulations to trucks over 26,000 pounds GVWR/GCWR or to trucks having 3
or more axles because several states had requested that coverage be limited so
that more stringent state regulations could be applied to the medium duty trucks.
However, limiting coverage to trucks over 26,000 pounds would exclude 56% of
all trucks over 10,000 pounds GVWR/GCWR from Federal regulation. Limiting
coverage to trucks over 3 axles would exclude 72% of all trucks over 10,000
pounds GVWR/GCWR from Federal regulation.
Even though only a small percentage (2%) of all medium duty trucks exceed
86 dB(A) at speeds under 35 MPH and 90 dB(A) at speeds over 35 MPH, the
actual number of trucks exceeding the standard is not small. Since the intent
of Section 18 is clearly to provide uniform nationwide noise regulation for all
vehicles involved in interstate commerce, and since limitation of coverage would
allow medium duty trucks to go unregulated in many states, the Agency has
determined that at this time medium and heavy duty trucks over 10,000 pounds
operated in interstate commerce shall be subject to identical Federal regulations.
61
-------
POTENTIAL DEGRADATION OF VEHICLES
Since a large proportion of medium duty vehicles nt the present time have
noise levels that arc considerably below W dK(.M :it speeds :U>o\e of> MIM1. \(
has been suggested tlwt degradation of these vehicles could occur until their
noise levels reach 90 dB(A) due to the promulgation of Federal regulations.
At the present time a few states enforce noise regulations equal to the proper" 1
Federal regulations, while in other states vehicle noise is currently unregulated.
Therefore, there is no a priori reason to believe that the change irom this situa-
tion to one of Federal regulation should cause any vehicle to become noisier than
it would be otherwise.
Nevertheless, some data are available that can be used to investigate the
likelihood of degradation at speeds in excess of 35 MPH. In Figure 10 surveys
of noise level distributions were presented for certain vehicle populations in
Washington State (1972), New Jersey (1972), and California before and after
state noise regulations were promulgated (1965 and 1971). Unfortunately, the
vehicle populations and other conditions (e. g. speed, grades, and measurement
sites) were not uniform in all states. The New Jersey and Washington studies
examined vehicles of 3 or more axles, while the 1971 California study examined
only combination vehicles. Since combination vehicles arc the heavier portion
of the heavy trucks having 3 or more axles, the California noise levels
measured in the 1971 study would be expected to be above the noise levels
measured in the other states.
An analysis of Figure 10 indicates that the 1971 California noise distribution
is about one decibel above the other distributions at noise levels below 84 dB(A).
The distributions are virtually identical between 84 and 92 dB(A) for all states in
all years and for all vehicle populations. Above 92 dB(A), the effect of the
California noise regulation is noticeable, since a smaller proportion of
of vehicles are currently above 92 dB(A) in California than in other states.
As expected, no evidence exists to indicate that vehicles degrade more
when regulated than when unregulated. In fact, since the California noise
level distribution for very heavy combination vehicles (tractor trailers) is
62
-------
only one decibel above the distribution of medium and heavy tiiicks in other
states, the state regulation may well have resulted in a reduction of the noise
emissions of trucks that were already below 90 dB(A) prior to regulation.
Testimony from muffler manufacturers during EPA public hearings indi-
cated that an increased demand for thnir better mufflers has been noted in
noise-regulated areas. These manufacturers and the American Trucking Asso-
ciation (ATA) indicated they had no reason to believe that degradation had
occurred in any states with noise regulations.
However, it is possible that when motor carriers replace the mufflers on
their vehicles in order to comply with the Federal regulation requiring an exhaust
system "free from defects which affect sound reduction,'' they will occasionally
choose a muffler that is not as good as the original equipment. This is unlikely to
occur \vilh nca\y duty trucks because it would lead to violation of the performance
standards. However, it could happen with some medium di.ly trucks that originally
'had noise levels below the standard. The agency investigated thii possibility of
.requiring a muffler "comparable to original equipment, " b'it this requirement was
determined to be undesirable because in many cases the original muffler supplied
on old trucks did not sufficiently attentuate noise, to meet the Federal emission
standards.
In the event that future studies of the noise levels of in-serve medium duty
trucks indicate that motor carriers are using replacement mufflers that are
inferior to effective original equipment, regulations can be developed to label
mufflers, and the Interstate Motor Carrier Regulations can be revised to require
the use of mufflers comparable or superior to original equipment. Muffler
manufacturers already provide information about the effectiveness of their mufflers
on specific engine models, although measurement methods vary to some degree.
Consequently, if degradation is found to occur, a remedy can be developed relatively
easily.
63
-------
Section 5
IMPACT OF THE FEDERAL NOISE REGULATIONS
Three kinds of potential impacts are associated with the promulg' '..ion of
the Interstate Motor Carrier Regulations. An economic impact will occur
because motor carriers will be required to retrofit those motor vehicles that
are not in compliance with the regulations. An impact on highway and urban
noise levels will occur because many vehicles will be made quieter. Finally,
some S'tates and local jurisdictions may be required to alter their existing
regulations because the Federal regulations are preemptive.
ECONOMIC IMPACT OF THE REGULATIONS
According to the analysis presented in Section 5, approximately 7-8% of
all registered trucks above 10, 000 Ib GVWR/GCWR will initially fail to comply
with the standards as measured at typical roadside sites. Until such time as
state and local jurisdictions adopt these standards as their own, the standards
will apply only to motor carriers engaged in interstate commerce.
There is no direct method for determining precisely how many trucks above
10,000 Ib GVWR/GCWR are engaged in interstate commerce. Based on truck
population statistics, industry information, and inputs to the Advanced Notice of
Proposed Rulemaking Docket, it appears that at least 1,000,000 of the 5,147,000
trucks above 10,000 Ib GVWR/GCWR will be affected (62.G3«64»65).
As discussed in Section 3, the heaviest impact of the standards will fall on
multiaxle trucks, and available statistics indicate that an average of $114 was
required in 1973 to bring these trucks into compliance with local standards that
were identical to the Federal Standards.
Since prices of most commodities and services have risen significantly over
the past year and appear likely to continue to rise in the next year, the average
retrofit cost can be expected to rise also. A reasonable average retrofit cort
estimate for 1975 is therefore $135 per vehicle in violation of the standards.
64
-------
If, as a worst case, it is assumed that all 5.2 million motor vehicles above
10,000 pounds GVWR/GCWR would be required to meet the standards, and that
8% of them would require retrofit at a cost of $135 per vehicle, then the total
direct retrofit cost could be as high as $56 million.
Although the number and composition of trucks operating in interstate
commerce is not known, most of the 5-axle trucks are thought to be used for
hauling intercity freight, and most of them are involved in interstate commerce.
Table 10 indicated that this group of trucks included half of all the trucks over
10,000 pounds GVWR expected to exceed the standards. Accordingly, the total
retrofit cost is likely to be at least $28 million.
In 1970, the average revenue per intercity vehicle mile for Class I intercity
carriers of all types was 91 cents. For Class I intercity carriers of general
freight, average revenue was $1.24 per intercity vehicle mile. Total expenses
for the latter group of carriers averaged $1.20 per intercity vehicle mile. Of
these expenses, wages represented 46 cents; repairs and servicing, 8 cents;
fuel and oil, 3 cents; tires and tubes, 2 cents; and depreciation and amortiza-
tion, 5 cents. Direct wages represent 38% of expenses per intercity vehicle
mile and 52 cents of every truck revenue dollar. Social security taxes, work-
men's compensation payments, and welfare benefits bring total wages to 60 cents
per truck revenue dollar* '.
A retrofit cost of $135 per vehicle is not a major burden for the interstate
motor carrier industry. For a truck running 50,000 revenue miles per year,
a $135 retrofit cost represents an increased expense of $. 003 per revenue
mile when amortized over a single year. When this increase is compared
with 1970 average expenses of $1.20 per revenue mile, it can be seen that
retrofit cost is not an obstacle to lower noise emission standards.
Additional costs include loss of revenue resulting from trucks being out of
service during retrofit. Also, the installation of a suitable muffler may in
some cases increase the back pressure on the engine and in turn increase the
fuel consumption. Considering the wide variety of mufflers available' ,
however, a significant increase in back pressure is avoidable.
65
-------
Some factors reduce the total cost to the trucking industry. First, the
muffler on a line-haul truck is normally replaced at 1-1/2 to 2 year intervals.
Thus, of those trucks that require a replacement muffler, about one-half will
be installing a new muffler even in the absence of the regulations. In these
cases, the cost incurred will be the difference between that for the required
muffler and that for the one that would have been installed anyway, aH the
difference is within the range of a few dollars. Secondly, Lr viiose trucks
requiring installation of a more efficient fan, the amount of engine power wasted
in driving a fan unnecessarily will be reduced. Standard fans on diesel engines
/got
typically consume 15 to 25 horsepower* . The addition of a thermostatically
controlled fan clutch can decrease fuel consumption by 1 to 1.5%' and can
reduce operating cost for the life of the truck. With these considerations, the
long-term cost of compliance with the noise regulations may be less than that
given above.
Component suppliers appear to be capable of providing the needed retrofit
components within the one year time period. The muffler manufacturing industry
is capable of significantly expanding its muffler production, probably by a factor
of two, because it already has the necessary facilities and material^ '.
In the case of tires a large majority of such trucks will require new tires
within a year regardless of the existence of the regulation. There should not,
therefore, be a significant increase in the total truck tire production required,
though there may be a slight shift in production from some tread patterns to
others.
Other retrofit items discussed in Section 3 are in current production, and
no significant problems are foreseen in meeting the production levels necessary
to retrofit the small percentage of trucks that will need these items in order to
comply with the standards.
ENVIRONMENTAL IMPACT OF THE NOISE EMISSION STANDARDS
The noise emission standards impact directly those trucks which presently
make the most noise and require that they be quieted to levels that are feasible
from a cost and technology standpoint within one year of final promulgation.
66
-------
The principal noise reduction will be of the intrusive noise peaks whh-h have
been widely acknowledged as more objectionable to people than much lower
(7V\
levels of continuous noise v ;. These peaks can be 12 dB or more above
ambient highway noise levels. Therefore, significant noise reduction
will be realized within a year, producing substantial benefits in terms of public
health and welfare as indicated by a decrease in community noise levels near
highways.
In a study performed under contract to the Environmental Protection
Administration ' ', L, levels were computed for an interstate highway, using
hourly traffic volume statistics submitted by the Maryland Department of Trans-
portation. This study was carried out using a modified version of the Highway
Noise Prediction Model of the Transportation Systems Center, U.S. Department
of Transportation. Baseline L. (day-night sound level) levels were computed
using actual distributions of noise levels for various classes of trucks as
measured in Maryland. Comparison levels were then computed using noise
level distributions corresponding to several alternative regulation strategies.
The results of the study indicated that a 90 dB(A) limit for all trucks above
10,000 Ibs GVWR/GCWR will produce a 3.6 dB decrease in L. for a typical
East Coast Interstate highway. This represents a decrease of about 50% in
the average sound energy near the highway.
An additional study of the impact of the Federal regulations has been per-
formed using the Highway Research Board Design Guide model. This model
is designed to perform an analysis of L (A-weighted equivalent sound level)
ecj
at 50 feet from the right of way of highways during the design hour. The
model was used to estimate the impact of the regulations in both highway and
normal urban conditions.
It was found that at 50 feet from a typical highway, the L during the design
eq
hours (peak hour) is 80.9 dB for cruise conditions. This analysis is predicated
on the following assumptions:
67
-------
(1) during the worst traffic hour there are 7200 vehicles per hour traveling
at an average speed of 55 m.p.h.
(2) the mixture of vehicles is 10 percent heavy duty trucks and 90 percent
medium duty trucks, light trucks, and automobiles.
(3) the typical highway has 6 lanes of traffic.
The effect of the Federal regulations will be a significant reduction in highway
noise levels. The results of the analysis indicate that 2 year* oxter the operating
rule goes into effect, the L for highways during the design hour will have beei
eq
reduced by 2.3 dB(A). The level will drop from 80.9 to 78.6 dB(A).
An analysis of normal urban conditions indicated that on city streets, the A-
weighted equivalent level is 68.1 dB for a mixture of 1 per cent heavy trucks, 6
per cent medium trucks and 93 per cent automobiles, traveling at an average speed
of 27 m. p. h.
The Federal regulations will affect only a few trucks on city streets because
most of the traffic on urban streets is due to automobiles and light or medium
trucks. Thus, the rule will bring about only a 0.3 dB(A) reduction in noise levels.
A significant reduction in urban noise levels will not occur until medium duty
trucks and automobiles are regulated to lower levels, since they are the dominant
noise source in urban areas.
RELATIVE STRINGENCY OF FEDERAL REGULATIONS AND THOSE OF OTHER
JURISDICTIONS
Jurisdictions with noise regulations planned or in effect have expressed an
interest in the relative stringency of the EPA regulations because their regula-
tions may be preempted by the Federal regulations. Test methodology and all
techniques of enforcement must be compared in order to assess different regula-
tions in terms of relative stringency. Maximum noise emission levels alone
can be very misleading.
A pronounced effect on noise as measured exists as a result of the surface
texture between vehicle and microphone. The EPA standards address this prob-
lem in that the stated levels apply to typical roadside sites with acoustically
soft reflecting surfaces between the vehicle and the microphone.
68
-------
Other factors affecting regulatory stringency in terms of measurement metho-
dology can be as important as site variation. Microphone placement has a critical
effect on measured noise levels. One city noise regulation calls for a microphone
location 25 feet from the lane edge. This is 31 feet from the lane centerline and
the regulated level would theoretically need to be 4 dB higher than the EPA standard
specifies in order to be of similar stringency (all other factors being equal). In
actual practice, at such close distances, ground surface reflections would result
in a difference less than 4 dB.
Another area of variability deals with enforcement techniques and policies.
The difficulty in assessing relative stringency is compounded by the fact that these
techniques and policies, as actually enforced, are sometimes not made clear by the
written regulations. A western State has a 90 dB(A) highway noise limit but has chosen
not to issue citations if the enforcement officers determine that tire noise predomi-
nates. As enforced, this standard would be less stringent than an identically worded
one in a jurisdiction enforcing against total noise emission. A New England State
has a noise regulation which appears to be as stringent as the EPA standards,
and which calls for increased stringency in the next year. Even though the wording
of its regulation calls for compliance under all conditions of grade and accelera-
tion, as does the EPA regulation, that State has chosen to enforce the regulation
under level-road, no-acceleration conditions. The actual violation rate is for
this reason much lower than the predicted violation rate for the EPA regulations
and therefore the actual stringency is less.
The categories of vehicles subject to different State and local noise regula-
tions vary. Those regulations which exclude certain classes of vehicles are less
stringent as applied than regulations which include these vehicles. Some local
regulations are based on measurement tests that are entirely different from the
Federal tests. Determination of the relative stringency in such cases would re-
quire extensive technical research.
Where measurement methodology is absent from a written regulation,
relative stringency cannot be determined. Tolerances in measurement condi-
tions or vaguely defined conditions (e. g., measurement distance defined as "50
feet or nearest property line") and the use of different frequency weighting
scales in different regulations also make comparison almost impossible.
69
-------
Table 11 presents information on the noise limits currently in effect in a
large number of State and local jurisdictions. Many of these jurisdictions
currently appear to have regulations identical to the Federal regulations, but
as mentioned, this can only be verified through a comprehensive analysis of
f
the test measurement and enforcement procedures used in each jurisdiction
70
-------
TABLE 11
TABLE E QUANTITATIVE NOISE
(Maximum
REGULATIONS FOR VEHICLE OPERATION
Levels at 50 ft)
-Limits Under
Vehicle
Type
Trucks
State, County, or City
California (over 6000 lb>*
Chicago (over 8000 Ib)
Colorado (over 6000 Ib)
Connecticut
Cook County (over 8000 Ib)
Idaho1"
Indiana (over 7000 Ib)
Minneapolis (over 6000 Ib)
Minnesota (over 6000 Ib)
Nebraska (over 10,000 Ib)
Nevada (over 6000 Ib)
New York
New York City (over 6000 Ib)
Oahu (over 6000 Ib)
Pennsylvania (over 7000 Ib)
Salt Lake County
(over 6000 Ib)
Level
Road
Only
82
82
82
All
Roads
Now
86
86
86
86
86
92
88
88
88
88
86
88
86
73-86
90
86
35 mph
Change
Year
1975
1975
1975
1975
1974
dB(A)
All
Roads
Then
84
86
86
86
73-84
Limits Over 35 mph dB(A)
All
Roads
Now
90
90
90
90
90
92
90
90
90
90
90
86
92
All
Change Roads
Year Then
1975 88
1974 84
*No citation if tire noise predominates
tAt 20 ft or more
-------
REFERENCES
1. Information on Levels of Environmental Noise Requisite tn j>rotect Public
Health and Welfare with an Adequate Margin of Safety, U.S. Environmental
Protection Agency, March 1974.
2. Ibid., p. 40.
3. Ibid., pp. B4-5.
4. Effects of Noise on People, NTID 300.7.
5. Truck Noise I - Peak A - Weighted Sound Levels Due to Truck Tires,
National Bureau of Standards Report prepared for Department of Transporta-
tion, Report No. OST-ONA 71-9, Sept, 1970.
6. Ibid.
7. Personal communication with W. H. Close, Department of Transportation.
8. Op. Cit., DOT Report No. OST-ONA 71-9, p. 3-4.
9. "Transportation Noise and Noise from Equipment Powered by Internal
Combustion Engines, " U.S. Environmental Protection Agency, Report NTED
300.13, Dec. 31, 1971, p. 94.
10. Ibid., p. 100.
11. Ibid., p. 102.
12. "Diesel Exhaust and Air Intake Noise, " Stemco Manufacturing Company for
Department of Transportation, Report No. DOT-TSC-OST-73, March 1973.
13. Ibid.
14. Data from Service Engine Company, Cicero, Illinois.
15. Op. Cit., NTID 300.13, p. 103.
16. Ibid., p. 102.
72
-------
17. Wyle Laboratories, personal communication with Flesc-A-Lite Corporation,
Tacoma, Washington.
18. Wyle Laboratories, personal communication with Advanced Products Group,
White Motor Company, Torrance, California.
19. Shipe, M.D., "Operating Principles of the Schwitzer Viscous Fan Drive,"
Schwitzer Division of the Wallace-Murray Corp., Indianapolis, Indiana,
March 1971.
20. Op. Cit., NTID 300.13, p. 103.
21. Published literature from Schwitzer Division of the Wallace-Murray Corpo-
ration, Indianapolis, Indiana.
22. Op. Cit., NTID 300.13, p. 104.
23. Ibid., p. 102.
24. Ibid., p. 104.
25. Law, R.M., "Diesel Engine and Highway Truck Noise Reduction," Society
of Automotive Engineers (SAE) Report 730240, Jan. 1973.
26. Op. Cit., Data from Service Engine Co.
27. Op. Cit., NTID 300.13, p. 7.
28. Ibid., p. 103.
29. Literature from Donaldson Company, Minneapolis, Minnesota.
30. Op. Cit., ODT-TSC-OST-73, March 1973.
31. Davisson, J.A., "Design and Application of Commercial Type Tires,"
SAE Paper SP 344, Jan. 1969.
32. Wik, T. R., and Miller, R. F., "Mechanisms of Tire Sound Generation,"
SAE Paper SP 373, Oct. 1972.
33. Wyle Laboratories personal communication with major tire companies.
34. Op. Cit., DOT Report OST-ONA 71-9.
35. Ibid., p. 42.
36. Ibid., p. 44.
73
-------
37. Ibid., p. 42.
38. Op. Cit., Data from Service Engine Co.
39. Op. Cit., NTH) 300.13, p. 92-95.
40. Close, W. H., and Atkinson, T., "Technical Basis for Motor Carrier and
Railroad Noise Regulations, " Sound and Vibration. Vol. 7, No. 10,
Oct. 1973.
41. Op. Cit., NTID 300.13, p. 92-93.
42. "Community Noise,I1 U.S. Environmental Protection Agency, Report NTID
300.3, Dec. 31, 1971, ppA-5, A-7.
43. Ibid., p. 4.
44. Op. Cit., NTID 300.3, pp. A-5, A-7.
45. Ibid., p. 5.
46. Young, E.W., "Single Number Criteria for Room Noise," JASA, 36, 2,
Feb. 1964, p. 289.
47. Klumpp, R. G., and Webster, J.C., "Physical Measurement of Equal Speech
Interfering Navy Noises," JASA, 35, Sept. 1963, p. 1328.
48. Wells, R. J., "A New Method for Computing the Annoyance of Steady State
Noise versus Perceived Noise Level and Other Subjective Measures," JASA,
46, July 1969, p. 85.
49. Webster, J. C., "Affects of Noise on Speech Intelligibility, " Proceedings of
Conference, Noise as a Public Health Hazard, Washington, D. C., June 1969,
ASHA Report #4.
50. Op. Cit., NTID 300.13, p. 94.
51. "Research on Highway Noise Measurement Sites," Wyle Laboratories Report
for California Highway Patrol, March 1972.
52. "Use of Motor Vehicle Noise Measuring Instruments," California Highway
Patrol Report, 1965.
53. "California's Experience in Vehicle Noise Enforcement," California Highway
Patrol Report, 1965.
54. Foss, R. N., "Vehicle Noise Study - Final Report," Applied Physics Labora-
tory, University of Washington, Report for Washington State Highway Commis-
sion, Department of Highway, June 1972.
74
-------
55. Unpublished data, Bolt, Beranek and Newman.
56. Op. Cit., "Use of Motor Vehicle Noise Measuring Instruments".
57. Op. Cit., Exhibit G., (ONAC Docket M070).
58. Op. Cit., "Vehicle Noise Study - Final Report".
59. Op. Cit., Unpublished Data, Bolt, Beranek and Newman.
60. 1972 Census of Transportation - Truck Inventory and Use Survey,
U.S. Department of Commerce, Bureau of the Census.
61. Ibid.
62. American Trucking Trends, 1972, by the American Trucking Associa-
tion, Inc., Washington, D. C.
63. "1973 Motor Truck Facts," by the Motor Vehicle Manufacturer Associa-
tion, Detroit, Michigan.
64. Response from American Trucking Association, (ONAC Docket M058).
65. Op. Cit., 1972 Census of Transportation Truck Inventory and Use Survey.
66. Op. Cit., American Trucking Trends.
67. Op. Cit., Literature from Donaldson Company.
68. Wyle Laboratories communication with the Schwitzer Division of Wallace-
Murray Corporation and the Flex-a-lite Corporation, 1973.
69. Bolt, Beranek and Newman, Inc., Report No. 2563, "The Cost of Quieting
Heavy Cab-Over-Engine Diesel Tractors," July 1973.
70. Op. Cit., Wyle Laboratories personal communication with 3 major muffler
manufacturers.
71. Op. Cit., NTID300.7.
72. Study conducted by Bolt, Beranek and Newman, Inc.
73. Maryland Department of Transportation submission to the Docket.
75
-------
Appendix:
MEASUREMENT METHODOLOGY
The procedures given herein are intended to permit measurement of the
A-weighted sound level of individual motor vehicles under spcciiied conditions.
The methods are consistent with the required accuracy of measurement.
Suitable instrumentation for the measurements is prescribed; standard (ideal)
measurement sites are described; and appropriate operational procedures are
given for carrying out the measurements.
Applicable Documents
ANSI SI. 4-1971, American National Standard Specification for Sound Level
Meters is appropriate for these procedures and is available from American
National Standards Institute, 1430 Broadway, New York, New York 10018.
Instrumentation
A precision sound level meter meeting all the requirements of ANSI SI. 4-1971
throughout the frequency range from 50 Hz to 10,000 Hz for a Type I or Type SIA
instrument should be used for all measurements. However, a magnetic tape
recorder, graphic level recorder, or other device to record maximum sound
level may be used for the measurement. In all such cases, the overall per-
formance of the total system should conform to the ANSI SI. 4-1971 requirements.
The necessary auxiliary equipment for the sound level meter includes a
mounting to hold the microphone at a height of 4 ft + 1 in (1.2 m) above the
ground, and a cable at least 15 ft (4.5 m) in length, designed to be used with
the sound level meter. The microphone manufacturer's instructions should be
followed concerning the maximum permissible cable length.
An acoustical calibrator of the microphone coupler type should be used for
calibration of the measurement instrumentation. The frequency of the calibra-
tion signal should be 1000 Hz, + 5%. The calibrator should be checked at least
annually by a method traceable to the U. S. National Bureau of Standards to verify
the correct performance within + 0.5 dB.
76
-------
A windscreen should be used for all measurements to reduce the effects of
turbulence at the microphone surface. An anemometer, accurate to within
+ 10% at 12 mph (20 kph), should be used to determine the local velocity of
wind gusts prevalent at the time of the measurements. The measurement of
wind velocity should be taken at the height of the microphone and approximately
10 ft from the microphone.
Calibration
The sound level meter (including the entire sound instrumentation recording
system) should be calibrated with the acoustic calibrator immediately before
each series of measurements and at approximately 1/2-hour intervals during a
measurement period. The manufacturer's directions for the calibration pro-
cedure should be followed. The entire measurement system, including all
cables, but not the windscreen, should be included in the instrument chain for
this calibration.
The entire measurement system should be calibrated, over the frequency
range between 50 and 10,000 Hz, at intervals not exceeding one year, by pro-
cedures of sufficient precision and accuracy to determine compliance with the
requirements of Section 3 of ANSI SI. 4-1971. If there is any reason to suspect
that the equipment has been altered or damaged, it should be given a complete
calibration, regardless of the date of the last complete calibration.
Standard Measurement Site
The measurement site for roadside pass-by and stationary tests should
be such that the vehicle radiates sound into an essentially open space above the
ground. This condition may be considered fulfilled if the site consists of an
open space free of large sound-reflecting objects (such as barriers, walls,
fences, hills, hedges, signboards, parked vehicles, bridges or buildings)
within the boundaries indicated in Figures Al and A2 for the pass-by and the
stationary vehicle measurements, respectively.
For the purposes of this requirement, "large" means dimensions greater
than about one foot (0.3 m). Objects that would not be considered "large," and
are therefore permitted within the measurement area, are fire hydrants, tele-
phone or power poles, and rural mail boxes, but not, for example, telephone
booths, or trees of any kind.
77
-------
Weather
Weather conditions may adversely affect measurement precision. Accord-
ingly, measurements should not be made during precipitation. The wind
velocity should be read from the anemometer immediately before each series
of measurements and at intervals of 1/2 hour during the measurement period,
if wind conditions warrant. Measurements should not be made when the
average continuous or gust wind speed exceeds 12 mph (20 kph).
Microphone Location
For all measurements, the surface upon which the microphone is located
should be within + 2 ft of the plane of the road surface. The microphone height
should be 4 ft + 1 in (1.2 m ^2. 5 cm) above the surface upon which it is located.
For the pass-by measurements the microphone should be located at a
distance of 50 + 1/2 ft (15 + 0.15 m) from the centerline of the nearest travel
lane. The microphone should have a clear and unobstructed line-of-sight to
the entire side of the vehicle for all points along the roadway within 35 feet of
the point of nearest approach.
For the stationary vehicle measurement the microphone shall be located
50 + 1/2 ft (15 + 0.15 m) from the fore-and-aft centerline of the vehicle, in a
plane normal to that centerline and passing within 3 ft (1 m) of the nearest
exhaust outlet.
Noise Measurement Procedures
The following procedures should be followed to assure accurate results in
the measurement of motor vehicle noise emissions:
(1) The microphone should be oriented with respect to the vehicle being
measured in accordance with the instructions or recommendations
of the microphone manufacturer for optimum flat frequency response.
(2) To minimize the influence of the observer on the measurements, no
person should be positioned within 10 feet of the microphone nor
between the vehicle and the microphone.
(3) All noise measurements should be made with A-weighting and the fast
meter response of the sound level meter.
78
-------
(4) The background noise at the site (namely, the noise level measured
with A-weighting and fast meter response due to all other sources of
noise except the vehicle being measured) should be measured from
time to time between vehicle passages. Vehicle noise measurements
should not be, made when the background noise level is within 10 dB of
the permissible noise standard for the measurement in question.
(5) Corrections for measurement at different altitudes above sea-level
should be made in accordance with the instructions of the microphone
manufacturer.
(6) For vehicle pass-by measurements the maximum sound level observed
as the vehicle passes through the measurement site should be recorded.
(7) For stationary engine run-up measurements the vehicle engine should
be accelerated as rapidly as possible from a low idle speed to maximum
governed speed with wide-open throttle, in neutral gear, and clutch
engaged. Measurement of the highest sound level that occurs during
the engine acceleration should be made at least twice, but more
measurements should be made if necessary to achieve a satisfactory
test.
79
-------
MICROPHONE v
LOCATION "*"
Figure A-l. Test site clearance requirements for pass-by test.
VEHICLE
EXHAUST(S)
ON THIS
LINE
MICROPHONE^
LOCATION
VEHICLE
FORE-AFT
CENftRLINE
Figure A-2. Test site clearance requirements for stationary
run-up test.
80
------- |