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         Background Document to
         PROPOSED INTERSTATE
            MOTOR CARRIER
              REGULATIONS

              as Published in the
      Federal Register Vol. 38, No. 144, Part 1
               NOVEMBER 8, 1973
       U.S. ENVIRONMENTAL PROTECTION AGENCY
              Washington, D.C. 2046O

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                                   550/9-73-005
        Background Document to
    PROPOSED INTERSTATE
         MOTOR CARRIER
          REGULATIONS
          as Published in the
Federal Register Vol. 38, No. 144, Part 1
          NOVEMBER 8,1973
               Prepared by
U.S. ENVIRONMENTAL PROTECTION AGENCY
    Office of Noise Abatement and Control
          Washington, D.C. 2O460
     This document has been approved for general availability. It does not
     constitute a standard, specification, or regulation.

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                        TABLE OF CONTENTS


                                                         Page

Seci.ion 1 - Statutory Authority                           1

Section 2 - Motor Carrier Industry                        4

Section 3 - Information Base for the Proposed             7
              Regulation

Section 4 - Categories of Interstate Motor Carrier       12
              Vehicles

Section 5 - Specific Noise Sources                       17

Section 6 - Noise Emission Standards                     35

Section 7 - Economic Impact of the Proposed Regulation   52

Section 8 - Environmental Impact of Proposed Regulation  55

Appendix A - Truck Noise Emission Data and Analysis      57

References                                               64

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                         LIST OF FIGURES
                                                       Page

Figure 1 - Propulsion System Noise Versus               20
             Vehicle Speed and Engine Speed

Figure 2 - Propulsion System and Tire Noise for         21
             a Typical 5 Axle Tractor Trailer

Figure 3 - Tractor-Trailer Noise Emission Distributions   22
             at 35 mph and over 35 mph

Figure 4 - Truck Noise Sources and Cab Types            25

Figure 5 - Peak A-Weighted Sound Level, as              34
             Measured at 50 Feet, Versus Speed
             for a Loaded Single-Chassis Vehicle
             Running on a Concrete Surface

Figure 6 - Estimated and Actual Cost Incurred in        48
             Retrofitting Trucks to Various Noise
             Levels

Figure 7 - Tractor-Trailer Noise Emission               49
             Distributions at 35 mph and over 35 mph

Figure 8 - Truck Noise Emission Road Side Survey        50
             Data for Speeds over 35 mph

Figure 9 - Tractor-Trailer Noise Emission               51
             Distributions at 35 mph or Less on
             Level Roadways

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                          LIST OF TABLES
                                                        Page

Tablt 1 - Estimated Costs to Retrofit Trucks to          37
            Various Noise Levels

Table 2 - Percentage of Trucks Exceeding a Given         38
            Noise Level During Typical Highway
            Operation—California Data

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                            Section 1



                       STATUTORY AUTHORITY




   RESPONSIBILITIES OF THE ENVIRONMENTAL PROTECTION AGENCY



     Through the Noise Control Act of 1972  (86 Stat. 1234), Congress



established a national policy "to promote an environment for all Americans



free from noise that jeopardizes their health or welfare."  In pursuit



of that policy, Congress stated, in Section 2 of that Act,  "that, while



primary responsibility for control of noise rests with state and local



governments, Federal action is essential to deal with major noise sources




in conmerce, control of which requires national uniformity of treatment."



As a part of that essential Federal action, Section 18 of that Act  (86 Stat.  1249)



directed the Administrator of the Environmental Protection  Agency  (EPA) to



publish proposed noise emission regulations for motor carriers engaged in



interstate conmerce.  MDtor carriers subject to such regulations include




common carriers by motor vehicle, contract carriers by motor vehicle and orivate



carriers of property by motor vehicle as these terms are defined by raragraphs



(14),  (15),  and (17)  of the Interstate Commerce Act (49 U.S.C.  303 (a).



     The EPA regulations proposed under  Section 18 of the Noise Control



Act are to include "noise emission standards setting such limits on noise



emissions resulting from operation of motor carriers engaged in interstate



co rrmerce which reflect the degree of noise reduction achievable through



the application of the best available technology, taking into account



the cost of compliance."  Final regulations are to be promulgated only after



consultation with the Secretary of Transportation, to assure appropriate

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consideration for safety and for availability of technology.  The regu-




lations are to take effect after such period as the Administrator of




EPA finds necessary, after consultation with the Secretary of Trans-



portation, to permit the development and application of the requisite;




technology.  Further, appropriate consideration is to be given to the cost




of compliance within such a period.  The regulations promulgated under




Section 18 may be revised from time to tine, in accordance with Subsection




18(a).  They shall be in addition to any regulations proposed for new




motor vehicles under Section 6.




RESPONSIBILITIES OF THE DEPARTMENT OF TRANSPORTATION



     After final interstate motor carrier noise emission standards have




been promulgated by EPA, the Secretary of Transportation is responsible




for promulgating regulations to ensure compliance with those standards.




This will be accomplished through the use of the Secretary's powers and




duties of enforcement and inspection as authorized by the Interstate Gomnerce



Act and the Department of Transportation Act.  These enforcement regulations




are to be promulgated only after consultation with the Administrator of




EPA.




ROLE OF STATE AND LOCAL GOVERNMEiSITS



     After the effective date of a regulation on noise emissions  from an




operation  of interstate irotor carriers promulgated under Section  18,  no




state or political  subdivision  thereof may adopt or  enforce a standard on




noise emissions  from the sane operation  that differs from the one promulgated




under Section  18.   State and local governments  may,  however,




adopt a standard identical  to  such a Federal standard




                                   2

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to add their enforcement capabilities to those of the Department



of Transportation.



     Further, interstate motor carrier operations not covered by Federal



regulations will remain subject to state and local noise standards and



regulations.  Such state and local regulations are limited, of course, by



the constitutional prohibition of state or local action that constitutes



an undue burden on interstate contnerce.



     Finally, nothing in Section 18 shall "...diminish or enhance the



rights of any State or political subdivision thereof to estabish and



enforce standards or controls on levels of environmental noise, or to con-



trol, license, regulate, or restrict the use, operation, or movement of



any product if the Administrator, after consultation with the Secretary



of Transportation, determines that such standard, control, license,



regulation, or restriction is necessitated by special local conditions  ^



and is not in conflict with regulations promulgated under this section."

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                          Section 2



                   MOTOR CARRIER INDUSTRY






      This  discussion briefly summarizes the organization,



 size,  and  economics of the motor carrier industry  in  order to



 provide  a  general perspective of the impact of EPA regulations



 on  that  industry.  There are over 15,000 firms in  the motor



 carrier  industry.  These firms are engaged in moving  both



 people and property.  The majority of their trips  are local,



 with  70  percent in urban areas or between adjacent counties. (1)




Those firms  involved in interstate commerce will be affected by the



proposed EPA regulations.





ORGANIZATION OF THE INDUSTRY
      The  industry is divided into two general classifications



 of  carriers:   1,   private carriers which use their  own   or



 leased  trucks,  to move their own goods, and 2. carriers  which



 provide transportation of others' freight.  The latter group of



 carriers  is further divided into  two  categories:   1.   common



 carriers—available to the general public to transport given



 types of  freight at published rates, between authorized  points,



 2.]   contract carriers—operate under contract with  one or more



 shippers  to serve their distinct requirements;.

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     The  proposed standards are applicable to those motor



carriers  meeting the  definition of common carrier, contract carrier,  and




 carriers  of property as set forth in the Interstate Commerce Act.






SIZE OF THE INDUSTRY



     The  motor carrier industry today is the largest transporter




of  goods  in this country.  In  1971,  the gross operating revenue




of  the  motor carrier  industry  (from the transportation of




goods)  comprised approximately 53  percent of the  total among




all regulated carriers.  Regulated carriers  include:  railroads,




motor  carriers, water carriers, oil pipelines,  and airways.




The industry can be characterized  as composed of  a large




number of small carriers competing with a few very large  carriers*




      The number of  trucks  and  buses engaged in the transport




of goods and people in  this country  has been steadily increasing.




During the period from  1960 to 1970, the  total number of trucks




and buses increased from  12.2 to 19.3 million, for an average increase


                              C521
of 0.7 million vehicles per year.v   '  Total miles traveled ner vear




have also increased.  For trucks specificallv, total miles traveled-




have increased from 90.5  billion in  1950  tn 206.7 billion in



1969.








ECONOMICS OF THE INDUSTRY
      In  1970,  the larger  intercity common carriers  of general

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freight had average  assets  of $3,243,000, average operating
revenues of $6,837,000 and averaaed $89,300 net income after
taxes. ^
     The average revenue  for large intercity carriers of  general
freight in 1970 was  $1.24 per intercity truck-mile.  Expenses
for these carriers averaged $1.20 per intercity vehicle-mile,
and of this, wages took     $  0.645  .  repairs and servicing
(maintenance) took   $  0.076    fuel and oil  $  o.03 (not
including State and  Federal tax), and tires and tubes $  0.019
cents.  The major cost  in carrier operation is, therefore,
operator wages, and  tires and tubes rank fourth.  Repairs
and servicing are approximately four times tire and tube  costs.
     The general economic health of the industry is reflected in
the  1970 financial  ratios  for large carriers, which include
4.96 revenue to worth,  o.oe profit (net after taxes) to worth,
and 0.013 profit (net after taxes)  to revenue. ^
                           -6-

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                             Section 3




            INFORMATION BASE FOR THE PROPOSED REGULATION




DATA ACQUISITION



     To develop the noise emission standards that constitute this




proposed regulation, it was necessary to establish a well defined




data base.  In connection with motor carriers engaged in interstate




commerce, this data base included the following information:




     1.  The existing noise levels produced by the various




         vehicles used by motor carriers under different




         operating conditions.




     2.  The degree of noise reduction possible on these




         vehicles, using available technology,




         together with the cost associated with this reduction.




     3.  The percentage of vehicles that  would require any




         particular treatment or modifications to achieve various




         noise levels.




     \.   The production supply of hardware necessary to achieve




         those noise levels.




     In order to gather and coordinate the input of the required




information, a Task Force was set up consisting of representatives




from various Federal and state agencies and consultants to the




Environmental Protection Agency.   The Task Force reviewed and analyzed




the data and developed recommendations for consideration by the Agency
                             -7-

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 in the development of the proposed regulations.   In addition,  the




 Agency amassed technology and cost information submitted to the official




 docket of the regulations as a result of the Advanced Notice of




 Proposed Rule Making,  and information previously developed by the




 Agency as part of its hearings under Title IV, P.L. 91-604. ^'-*






 AVAILABILITY OF DATA






      In general, the main sources of existing highway noise data were



 the Federal and State government agencies and knowledge of  EPA consultants




 Although a certain amount of retrofit information was available from




 the vehicle manufacturers, a greater source was the individual component




 manufacturer.



       Data were analyzed from 5838 diesel trucks operating on  freeways




in California in 1965,  531 trucks in the state of Washington in 1972,




and fron 1,000 trucks in New Jersey in 1972.8  These data, collected



before the California noise regulations took effect, and from states




not having noise regulations, were considered to be representative of



existing (1973)  noise levels from trucks operating on freeways  in




states not having noise regulations.




      The noise level data for trucks accelerating at low speed (less




than 35 mph), were taken from 776 trucks in California in 1971   and from
     *Since the regulations were proposed on July 27,  1973,  additional



data have been gathered from eight other States.   See  Appendix A.
                             -8-

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 239 trucks in the State of Washington in 1972.'  For constant speed



operation at speeds less than 35 miles per hour, data were obtained from 340


                             9
trucks in California in 1971.



      An additional part of the data base consisted of noise levels



measured from stationary trucks by means of an engine run-up technique.  The



data were obtained on 877 trucks by the Society of Automotive Engineers



Vehiclj Sound Committee.   There was a paucity of data on the levels of



noise emitted by interstate motor carrier vehicles other than large multi-



axle trucks, which are primarily powered by diesel engines.  It is known,



however, that vehicles such as gasoline trucks and buses are inherently



quieter thin large multi-axle diesel trucks, and should have no difficulty



in complying with any noise emission standard which is reasonable for the


         (98 99}
latter.    '  ' The proposed regulation applies to all interstate motor



carrier vehicles over 10,000 pounds GVWR or GCWR.  Additional data will be



obtained in the future so that subcategories of those vehicles, such as



gasoline trucks and buses, may be treated separately in future revisions of



the regulation.



      Data on auxiliary equipment of motor vehicles were also limited.  Manu-



facturers have submitted some information on the noise emissions from typical



refrigerator units,   but additional data will be developed for possible in-



clusion in subsequent revisions of the regulation.



      the remainder of this Background Document is based upon an analysis of the



data described in this section.



MEASUREMENT METHODOLOGY DEFINED



      The proposed regulation concerns the noise emitted by motor vehicles



engaged in interstate commerce.  In order to set a meaningful regulation based



upon specific noise level standards, it is necessary to specify an appropriate



method for characterizing and measuring the noise emission from an individual



vehicle.  This entails defining the operation of the vehicle under measurement



as well as the method by which the measurement is conducted.



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     In general, there are two main conditions under which motor




vehicles operate, namely




     1.  Urban driving at low speeds




     2.  Highway driving at high speeds




     In urban areas, the vehicle is seldom allowed to exceed a speed




of 35 miles per hour, except in the western area of the nation where speed




zones of 45 miles per hour are common.   On the open highway, and on




urban freeways, vehicle speeds are limited to a range  of from  about  55 to




70 miles per hour.  Subsequent sections of this background document will




show that the noise characteristics of  motor vehicles are different




in the two operational conditions.  Therefore, the proposed  regulation




will include separate noise standards for these two conditions«i.e.,




the two speed ranges.  However, if the  actual vehicle speed  is specified




in the regulation, then subsequent enforcement would require simultaneous




measurement of this speed .along with the noise level produced.  1b remove




this obstacle to enforcement in the proposed regulation, the speed zone




in which the vehicle is operating, rather than the actual speed of the




vehicle under measurement, is specified in the proposed regulation.



     For the noise standards to be meaningful it is necessary to




specify the noise level at a given distance produced by a truck when




it is  operating under the conditions just  discussed. In the proposed




regulation, all references to a quantitative method for specifying the




magnitude of a noise are in terms of the A-weighted noise level scale,
                                -10-

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the units being in dB(A) .  A-weighting corresponds




approximately to the way in which a person hears a noise and is  effected



by  means  of a  simple electrical  circuit contained  in most sound



             1 ?
level meters.    Other scales are available, but they require a more




complex analysis, which is  normally not  justified by the improved




correlation with human assessment.




     The standard measurement distance  selected is 50 feet.   This  is




consistent with current recoimended practice, for the measurement  of




both the noise from new vehicles   and  the operational noise levels




from vehicles on the highway   in various states and cities.  The




distance of 50 feet is a compromise between 25 feet (the ISO  standard




distance), at which  slight variations  in vehicle distance can lead  to




significant errors in the  measured noise level, and greater  distances




at  which  background noise and nearby reflecting obstacles can pose  a




problem in measurement site selection.    Furthermore, almost all  of




the data base consists of  noise levels measured at this distance.  There




may be some occasions when a measurement at 50 feet is not  possible or




undesirable; for example,  urban or suburban areas with nearby acoustically



reflecting surfaces which  could distort the measurement.  Alternative




measurement distances together with suitable correction factors to




standardize to a measurement distance of 50 feet can be specified    in




the enforcement procedures established for these proposed regulations.  The



enforcement procedure should also specify the criteria for selecting




suitable highway measurerrent sites.






                               -11-

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                               SECTION 4



             CATEGORIES OF INTERSTATE M3TOR CARRIER VEHICLES





     Interstate motor carriers utilize a broad range of vehicles;  from



small two-axle "straight" trucks and buses up to    "combination"  ( tractor-


                                      (18)
trailer) trucks  with 5 or more axles.v  '   All of  these vehicles  contribute to



noise emitted along highways and streets,  which sets the ambient noise  level in


                       (19)
most urban communities.     But large motor carrier vehicles cause a nod.se



problem that can be separated from the  problem of motor vehicls noise



in general.  At the present time, diesel trucks emit noise  levels



that are so much higher than those emitted by other



motor vehicles that they stand out very noticeably.  Ifoise  peaks of



12 dB    above the ambient noise level from other traffic are  common. ^   '



It has been widely acknowledged that such noise peaks are more objectionable



to people than is the ambient noise.'^1)



     Trucks weighing less than 10,000 pounds gross  vehicle  weight  rating  (GVWR)



typically produce noise levels ranging  from 64 to 72 dBA at 35 mph, when measured at


50 feet.  This correlates closely to the noise level produced  by ordinary



passenger automobiles, which generate  up to 68 dB(A) at 50 feet at the



same speed.'  '  Such a result is not surprising since the  basic noise-



producing components of such small trucks are little different from those



of automobiles.  They are powered by gasoline engines similar



in most respects to automobile engines; they have two-axle  chassis, and



they usually use rib tires similar to automobile tires.



     Trucks of over 10,000 pounds GWR  or Gross   Combination Weight  Rating


 (GCWP) for combination vehicles, on the other hand, are different  from  small
                               -12-

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trucks and automobiles.  They can produce noise levels of  95 dB(A) or more at




highways speeds when measured at 50 feet.(23'8'  Their hioher noise level can be



accounted for by their canmon use of relatively noisy diesel engines  instead of



gasoline engines, their frequent employment of three, four, and five  axle  designs




using more noise-producing tires, and their occasional use  of  "pocket retread" tires,



which produce more noise than other tire designs^  '  (see discussion  of



tire noise below).



     Moreover, trucks of over 10,000 pounds GWR or GCWR are typically



used for long distance intercity and interstate hauling.  They are,



therefore, operated many more miles per year on the average than small



trucks, which are usually used for general service and delivery work


                                  (2^
within one relatively small area.v  '  Indeed, many small trucks are



devoted to individual uses not unlike private automobiles.   The vastly



greater mileage traveled on an average by large trucks than by  small



trucks and automobiles causes the former to make up a much  larger



percentage of vehicles actually observed on the road than would be



indicated by the percentage  they constitute of  the  total  vehicles



registered.*  As a result, efforts concentrated on reducing the noise of



large trucks will have a proportionately greater effect than might be



determined from truck registration data.



     All of these aspects of large trucks—their relatively high con-



tribution to the noise problem, their design, their typical use, and  their



high average mileage—which distinguish them from small trucks  and
     *See Appendix A.
                              -13-

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automobiles indicate that they should be the focus of EPA efforts under

Section 18 at this time.  The problem of noise from small trucks appears

to be more appropriately handled in the same way as the noise from the

automobiles they resemble in design and use;  for example,  through such, new product

standards as those of Section 6 of the Noise  Control Act and through vehicle use

regulations of State and local governments.   If in the future it appears

that the operation of smaller vehicles should be regulated under Section

18, the regulations may be revised pursuant to Subsection 18 (a).

     The dividing line between large and small trucks  has been drawn at

10,000 pounds gross vehicle weight rating or gross conbination weight

rating* because virtually all trucks  designed and  used much

like passenger cars, are below that weight, while few trucks with signifi-

cantly different characteristics, such as diesel engines,  multiple axles,  and

 significantly higher noise emission levels,  are below that weight.  Moreover, a

 break at 10,000 pounds is convenient because most states  use that weight as a

 boundary in their vehicle registration categories.  In addition it is a

standard weight category distinction used by  DOT in their safety regulations.

 Compatibility  with  the present DOT weight categories  is advantageous

since DOT is the Federal enforcing agent.
     *"Gross vehicle weight rating," GWR,  is defined for single vehicles;
whereas "gross combination weight rating,"  QCWR,  is defined for combina-
vehicles such as tractor-trailer trucks.
                              -14-

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     The category of interstate motor carrier vehicles over 10,000 pounds




 includes many vehicles between 10,000 and 33,000  pounds GVWR or GCWR




 powered  by large gasoline engines,  as well as virtually all of  the




 interstate motor carrier vehicles powered by diesel engines.  As will




 be discussed in the section on truck noise characteristics,! diesel




 engines are inherently noisier than gasoline engines.  In  addition, as




 a rule, diesel engines are used in heavier trucks that have other more




 noisy components, such as a greater number of tires, than trucks powered




 by gasoline engines.^  '   Buses, whether diesel or gasoline, are also




 inherently quieter than trucks because of design  features  such as more




 fully enclosed engine compartments (see Section 6).




     Since large multi-axle diesel trucks  pose the roost severe motor




vehicle noise problem,  the vast majority of the work done on motor vehicle noise



 has been directed at them.  Thus, the data discussed in Sections 5 and




 6 of this document aro in large part derived from, and specifically




 applicable to,  large multi-axle diesel trucks.  The noise  emission




 standard based on the analysis of those data is,  therefore, one  that  is



 most appropriate for trucks with more than three axles.  This is borne out




by the data presented in  Appendix A, which show the highest proportion



 of vehicles in violation of the proposed standard to be trucks with three



 axles or more,  which are  often diesel powered.




     It might be argued that since this is the case, the category of




 large motor carrier vehicles should be further subdivided  to reflect
                             -15-

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different noise standards for gasoline versus diesel trucks, buses,



and any other relevant categories.  Further distinctions could be made



on the basis of the age of trucks, and for new trucks, to reflect the



degree of noise reduction that  each class of truck can achieve.  This



approach has considerable merit  and is being carefully considered



for use in future revisions of the interstate motor carrier noise



regulations.  At present, however, the available data on vehicles other




than large multi-axle diesel trucks  are  not sufficient to permit the



selection of different noise standards for them.  Since large multi-



axle trucks are the most severe noise problem, and since much of the



possible noise abatement technology, such as mufflers and cooling fans,



is basically the same for all large vehicles, a standard that  is



reasonable for multi-axle trucks can be assumed to be feasible for




other large motor carrier vehicles.  (See references 58 and 59) .



Applying the same standard to other large motor carrier vehicles



on an interim basis, while more specific data is gathered for them,



will limit any increase in their noise emissions.
                                   16

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                               Section 5


                         SPECIFIC NOISE SOURCES
     This section of the document describes the noise characteristics


of large motor carrier trucks and the methods available for effecting


noise reduction.  It specifically discusses trucks because, as indicated


in Section 4, they are the most severe noise problem, most of the available


data concerns trucks, and any regulation  that is reasonable for trucks


will be reasonable for other large vehicles.  The noise produced by a


truck is dependent on the type and the quality of the component parts.


Large trucks are not standardized as are  automobiles.  Specialized


user   needs result  in a greatly varied assembly of  truck components,


especially with respect to powertrain and related equipment.  As


a result, the noise  produced can vary considerably from vehicle to


vehicle.  To illustrate the extend of the variation  that can exist,


the following discussion of noise sources is preceded by a brief


description of truck components.
        C^^ACTERISTICS OF LARGE TRUCKS
     Virtually all trucks in excess of 10,000 pounds GWR or QCWR are


powered either by gasoline or diesel engines; those in excess of 33,000

                                                                      / 28}
pounds GVWR or GCWR are powered almost exclusively by diesel engines.


Diesel engines may be naturally aspirated  (air introduced at atmospheric


pressure), turbocharged ,or supercharged by the engine itself.  The engine


is  located at the front of the cab in a conventional style  (C) and under


the cab in a cab-over-engine  (COE) style truck.
                                   17

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     Ihe engine exhaust for both engine types 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."  The latter is often




preferred so as to direct exhaust fumes away from motorists and




pedestrians.  Single or double 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 style.  In the latter




case, it may be on the same or opposite side of the cab as the eshaust




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.




This torque is usually applied to either one or two drive axles on the




vehicle.  The number of axles on the entire vehicle, including the




trailer, depends upon the load to be hauled, and varies according to




State regulations.  The result is that the number of tires on a heavy



truck-trailer combination can range from 10 to 42.







TRUCK NOISE CHARACTERISTICS



     Many combinations of components exist that affect the total noise



                 (29)
level of a truck.v  '  This is true not only for trucks designed




specifically to perform different tasks, but also for trucks designed to




perform similar tasks.  The reason for the variety is the very marked




owner preference in the trucking industry—a preference based on actual




performance, imagined performance, or simply a traditional attachment to




a given model configuration.
                                    18

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     The noise from the propulsion system is not the only contributor



to the overall noise level.  At speeds greater than about 45 miles per



hour, additional noise of significant magnitude compared to the propulsion



system noise is produced by the interaction between the tires and the



road surface. ^  '  The relationship between propulsion system noise and



tire noise as a function of vehicle speed is shown in Figure 2.   '




In this figure, the noise levels produced by both the propulsion system



and the tires are shewn as functions of vehicle speed.  There are 2 fairly



distinct vehicle speed ranges in which the noise level can be characterized.




At speeds less than 45 miles per hour, the overall noise level for a



truck fitted with a typical conbination of tires is determined mainly




by the contribution from the propulsion system, which is independent of



the vehicle speed.  At speeds greater than 45 miles per hour, a major



contributor can be tire  noise, which increases with vehicle speed.



The vehicle 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.



     The effect of vehicle speed on the noise levels produced by one



type of truck operating on the highway is shown in Figure 3.  This



Figure presents the cumulative distribution of the noise levels from



tractor-trailer trucks operating at lew and high speeds.  These data




were taken in  California,  where noise regulations are in existence.   The




data shown in Figure 3 are therefore not necessarily typical of the nation.



since the Califorina noise regulations may have reduced the number of noisv



trucks in that State.   The basic distinction between low and high speeds,



however, is typical.   The difference
                                   19

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                                                                                .£>
                                                                                                                   O
                                                                                                                   CL
                                                                                                                   0)
                                                                                                                   0)
                                                                                                                   V)
                                                                                                                  •—
                                                                                                                   O

                                                                                                                  Z
                                                                                                  o
                                                                                                 Ic
                                                                                                                    .
                                                                                                                   O
                                                                                                                   4~-
                                                                                                                   o
                           9P  y

-------
                                                                           21
  100
   90
o
in
I
0)
w
•H
•&
   80
   70
                                    Tire Combinations:


                     Steering Axle    Drive Axles
                    O  New Ribs
            1/2 Worn X-Bars
                                  Trailer Axles
       New Pocket Retread
                    p  New Ribs
            New X-Bars
       New Rib Retread
                    A,  New Ribs
            New Ribs
       New Rib Retread
Engine Related Noise Alone

thru 12 Gear Steps
                                                                       Tire Noise Alone
   60
                   10
         20
30
40
                                                                               50
                                      Vehicle Speed, mph



                    Figure 2 - Propulsion System and Tire Noise for a

                               Typical 5 Axle Tractor Trailer


                               (from reference 31 and 32)

-------
          DATA SOURCE

          a CALIFORNIA  (1971) 172  TRACTOR-TRAILERS

                              "OVER 35 MPH"

          A CALIFORNIA  (1371) 145 TRACTOR-TRAILERS

                              "35  MPH OR LESS"
    loop r n i in i
GO LU
LU in
_l t—I
CJ> O
t—I ~
:r
U,

O
  LU
  O
  X
  LU
                                                         no
               70        80        90        TOO


                   NOISE LEVEL  d3 (A) AT 50 FT


Figure 3 .  'Tractor-Trailer Noise Emission Distributions at 35 nph and over 35 irph
                               -22-

-------
 in noise level in the two speed ranges is due mainly to the increased
 level of the tire noise contribution.
     This completes the summary of overall truck noise characteristics
 as a function of operation.  Next, the individual truck components that
 contribute to the overall noise level are discussed.

TRUCK COMPONENT NOISE SOURCES, ABATEMENT, AND COSTS-
     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 are as follows   ' (not necessarily in
 order of importance)—see Figure 4.
            Engine system
            Engine cooling fan
            Engine (mechanical)
            Air intake system
            Transmission (gearbox, drive shaft, rear axle(s))
            Engine auxiliary equipment
            Tire/roadway interaction
            Aerodynamic flow
            Brakes
     Of these, the first four sources are of major importance for trucks
of concern here when traveling at low speeds^  '  (less than 45 miles per
hour).  At higher speeds (greater than 45 miles per hour)  tire noise
assumes a much greater significance.  A brief discussion of these major
sources is contained in the following sections.
                                   23

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Exhaust  System




Exhaust  noise  is created  when  engine exhaust gases  excite  oscillations



in 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 addi-




tion to the radiation from the end of  the tail pipe, noise is also




transmitted through the exhaust  pipe and muffler walls.  Noise is also




produced by the application of engine  brakes  (with trucks so equippped)




ti. c, when in use,  provide a retarding force on the engine that reduces




the   5eed of the truck.  Typical exhaust noise levels range from 77 to



oc; IV  ;  at 50 feet irrespective of  speed  ^29^ and are usually greater in




 i:ucks that have been poorly maintained.



      Although the  exhaust system is a major noise source, the associated




 ,,oiS'_ levels can be reduced 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.  Besides the muffler, considera-




 tion can also be given to wrapping  the tail and exhaust pipes with insula-




 tion.  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 insertion loss of the:




 muffler is increased.   Muffler  specification and suggested exhaust system




 configurations are currently offered  by major muffler manufacturers for




 almost every engine,  since no universal muffler exists  that is the best




 for all types of engines.
                                   24

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   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 4.  Truck Noise Sources and Cab Types
                       -25-

-------
      Exhaust noise,  using the best available mufflers, typically ranges



  fron 72.5 to 80 dB(A)  at 50 feet for today's most popular



 diesel engines.'36'   These mufflers  provide insertion losses of from



 9.5 to 27 dB, and are of the type installed on new trucks as standard


           (36)
 equiorent,       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. ^36'       for maximum effect  it is necessary to replace  existing



 flexible exhaust pipes with rigid pipe  and slip joints at a cost of about



 $45 per side including labor.



      A sudden increase in demand for replacement  mufflers would not



 pose a significant problem to the manufacturers,  many of whom are  at



 present expanding their facilities to increase their output by  a. factor



 of 1.5 to 2.(38>



"Cooling Fan


      Trucks generally use axial fans to draw air  through a  front-



 mounted radiator to provide water ccoling/ which in turn  provides engine



 cooling.  Fan noise is the result of air flow irregularities and is



 partially governed by the proximity of  shrods, radiators, grills,

                          (39)
 radiator shutters, etc.     The noise  produced by the fan  is related



 to fan tip speed.  Most diesel engines  for heavy  trucks  are rated  for



 maximum horsepower at about 2,100  rpm.   At this speed, engine cooling



 demand is greatest and the fan can very easily be a  major contributor



 to the overall truck noise level.   Typical truck fans usually exhibit



 noise levels in the range of 78 to 83 dBA. at 50 feet at rated engine


     ^   (29)
 speed.
                                   26

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     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 lower speed.  In many cases this may also



require the installation of a larger radiator, which could result




in an expensive modification to the front of the engine compartment.



     It is more feasible to install a fan blade that produces less



noise, while at the same time allowing for adequate cooling.  Most exist-




ing fans are stamped out of sheet 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 particularly efficient in perform-



ing its task.  In many cases it can be replaced with a more sophisticated



design that affords a noise reduction  from the fan alone of from 7 to



12 dB.(4°)  The cost is in the range of $30 to $35 installed. ^41^



The overall truck noise can also be reduced by about 1 dB in some cases



by incorporating a venturi-type shroud around the fan with a small



tip clearance at an installed price of about $45.



     Trucks are designed to be able to cope with heat rejection of



maximum engine power with little or no ram air.  Since ram air increases



with truck speed, fans become proportionally of lesser importance



at higher speeds and could be slowed or stopped in many instances.



The critical condition occurs when — as in pulling a heavy load up



a long grade—the truck is moving slowly in a low gear but the engine



is developing full horsepower.  Trucks, unlike automobiles, usually
                                   27

-------
do not have an overheating problem when the vehicle is stopped and
the engine idles at low rpm.  As a result of these characteristics,
there are only a limited number of conditions under which additional
cooling is required.  When,  the fan is needed only a small percentage
of the total engine on-time, there are certain types of fans avail-
able  that rotate only when this additional engine cooling is required
and  that idle when the cooling due to ram air flow is sufficient.
Typical fans of this type incorporate a thermos tatic clutch or a
viscous fluid drive. Viscous  fluid-clutched  fans permit the  far to
rotate at reduced speeds when not needed.  They offer some fan noise
reduction (about 3 to 10 dB) but the on-of f mechanical clutch would be
preferred because of the total elimination of  fan noise while the fan is off.
     T/pical costs for a viscous clutch are about $225 plus about
$15  for  the suggested fan blade. (43)  A thermostatically controlled
unit including the necessary fittings  costs typically on the order
of $285  to $360, plus $40 to $50 for installation. (37' 43)

Engine(Mechanical)
     Engine mechanical noise in internal combustion engines is produced
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
produces mechanical  vibrations in the engine structure that are trans-
mitted through the cylinder walls, oil pan, rocker arm, covers, etc.
 Some of  the vibrational engery is subsequently radiated in the atmosphere
 as acoustic energy.
     Gasoline engines initiate combustion with a flame that smoothly
                                   28

-------
spreads 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.


Ihis 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,


noise levels from diesel engines often are as much as 10 dB greater


than those from gasoline engines.  (44)  rphe engine noise contribution
in typical diesel-powered trucks is on the order of 78-85 dBA.  ^ **


Turbochargers are often used to increase the pressure of the intake


air.  This reduces the pressure fluctuations in the engine, which in


turn lowers the engine noise level. (44)  The devices used to increase


the pressure may in some cases contribute to the overall noise level;


i.e., turbocharger "whine."  Retrofit methods of reducing the noise


produced by engines generally fall into one of two categories:


     i.  Reduction of noise radiated by the engine by


         modifying certain exterior surface covers.


     2.  Installation of acoustic absorption and barriers


         in the engine enclosure.


Engine noise reduction kits suitable for retrofit applications to


limited 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 noise only (as opposed


to total vehicle noise level) at a cost of between $50 to $100 for

         (45)                                     /-v^
material      and, typically, $30 for installation. ^''  Such kits
                                   29

-------
are in limited production at this time and have not undergone

                             (52)
complete durability testing.       They will be considered for


suitability and availability whenever the proposed regulations are


revised.


Air  I nduc tion  S vs t em
               system noise is created by the opening and clos:Lng


of the' intake valve , which causes the volume of air in the system to


pulsate.  The associated noise levels are dependent upon the type of


engine, the engine operating conditions, and whether it is turbocharged


or naturally aspirated.  ^39'  Typical intake noise levels vary from


70 to 80 dBA.


     Intake noise reduction technology is very similar to that for


exhaust noise reduction.  Major manufacturers are able to provide


assistance in proper selection of air intake systems for all popular


engine models.       Retrofitting the intake systems of trucks in


service' consists of replacing older air cleaners with modern quality,


dry element air cleaners.  This would result in a cost of $100 - $130,


on the average .       Intake cleaners and silencers are manufactured


largely by the major muffler manufacturers, so that the production


could be increased  as described in the above discussion of mufflers.


_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) .  Rib tires  have the tread principally oriented longitudinally


around  the tire  (similar to automobile tires) .  This is the most


coimon  type of truck tire and can be used in all wheel positions;
                                    30

-------
however, they are almost exclusively utilized in steering axle  positions



because of their superior lateral traction and uniform we a if characteristics.



Crossbar designs have the tread elements principally arranged laterally



and are popular for use on drive axles.  These designs provide for


                                                                    (47)
up to 60 percent more tread depth due to the rigid cross elements.  v  '



     The physical mechanisms of the production of noise by  tires and



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 vibration of the tire



contributes to the total noise level.  *  '  However, the effect of



the large lugs on crossbar tires, and the effect of the road surface



on the noise levels produced are not well quantified.  The  result is



that basically all the noise information available has been obtained



experimentally, and the tire manufacturers do not appear to be



close to any major breakthrough that would result in crossbar tire design



exhibiting significantly lower noise levels.



     There seem to be no conclusive data that, indicate any



significant difference between the traction properties of rib and



crossbar tires under dry, wet, or icy conditions. ^49^  Any difference



is possibly in favor of using rib tires because they normally provide



about 5 percent 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, there is an advantage to  installing



crossbars. '  '
                                    31

-------
     There is no conclusive economic preference to the use of crossbar
or rib tires.       A rib tire has a tread depth on the order of 17/32
inch and costs about $100.  Its life is about 50,000 miles if it is
worn down to 2/32 inch on a drive axle.  An equal quality crossbar
tire costing about $130 may have an initial tread depth of 27/32 inch
and last typically 100,000 miles when reduced to 2/32 inch.   At this
point, some firms sell the carcasses (the rib possibly being worth more
in this case) and buy new tires.  Under this policy it is more
economical (54 percent more mileage per dollar) to use crossbars.
However, other firms choose to spend about $30 to recap the rib tire
with an additional 17/32 inch tread and use it again, obtaining an
overall life of 100,000 miles at a total cost of $140—the same as
the original crossbar type.  If the crossbar and rib carcasses (of
equivalent quality) have been subjected to the same abuse, then they
will have essentially the same number of miles left in them.  Some
trucking companies will use only new tires on drive axles and when
they are half worn they will be removed and used on a trailer
position until completely worn.  They will then be recapped.  Rib
tires are thought by some to wear more quickly than crossbars in drive
axle positions.
     Extensive measurements of the noise level produced by tires mount-
ed on the drive axle of a truck-tractor have been conducted by the
National Bureau of Standards and the Department of Transportation.
—see figure 5. ^1)  Typical values of the noise level measured at
                                    32

-------
50 feet are 68 dBA and 73 dBA at 35 miles per hour for new ribbed
                                                                  I
                                                                     (51)
and crossbar tires respectively on a concrete roadway.       At 50
miles per hour these levels typically increase to 73 dBA and 80 dBA
respectively, although higher values are by no means uncommon.  In
general, ribbed 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.
     Data indicate that some retread tires  that exhibit a tread
design composed largely of pockets  that 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 exceeding 90 dBA at highway
speeds. (51)
                                  33

-------
                  SPEED, KM/HR

         50   60    70   80    90    100
      NEW TIRES
      CONCRETE
      LOADED VEHICLE
      AT 50 FEET
                                    POCKET
                                    RETREAD
                                              CROSS-BAR
                                               RIB
                  40        50

                   SPEED, MPH
                           60
Figure 5.
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 qraph.
These were mounted on the drive axle.
                      34

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                                 Section 6
                         NOISE EMISSION STANDARDS

NOISE LEVELS FOR LARGE INTERSTATE M3TOR CARRIER VEHICLES
      The noise control information given in the preceding section corresponds
 essentially to the state of available knowledge of retrofit technology for
 each individual noise source.  To reduce the noise level  produced by an
 existing vehicle,  it is necessary to apply one or more of the modifications
 outlined—the nurrber or type of modifications, depending upon the
 vehicle in question and the overall noise reduction required.   For
 example, more components of an old or poorly maintained truck would
 normally need to be modified than those of one in newer condition.
 Similarly, more treatment would be required to reduce the noise level of
 a vehicle to 84 dB(A)  than would be required to reach 88  dB(A) .
      As stated in  the discussion of motor carrier vehicle categories,  most
 cf tfte available data concerns large to'ckr, "-ith  Uireo ov -r>rr ax.".o,«r
 which are predominately diesel powered.  Knowledge of some noise sources,
 such as tires, is  of course applicable to other vehicles  such as gasoline
 powered trucks and buses; and it is probable that knowledge of other noise
 sources such as cooling fans will prove applicable to all large vehicles.
 But the specific information- available at present does not permit an
 enumeration of specific treatments, with associated
                                   35

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costs, to produce predictable amounts of noise reduction for vehicles



other than large multi-axle trucks.  The data nrpsp-ntpd in Tables 1 and




2 and Figures 6, 7, 8, and 9 in this section are based upon studies of




larqe multi-axle trucks t^at ar^ nrimari.lv rh'.efiel nnwprpd.  AK discussed in




Section 4, it can be assumed that any noise standard that is reasonable for



such 1araF> trucks is feasible for other rrotor carrier vp>hirlpiQ, -i nr-1 nrl -i nrr
     Types of treatment  that might be required to reduce noise emissions



 (other than noise emissions from the tire/road interaction  from trucks



to various levels, and the associated costs per treatment,  are listed



in Table 1.  The levels indicated correspond to noise emission at maximum



engine speed  (where noise other than tire noise is highest) , measured at



50 feet.  Since the noise levels of individual existing trucks vary,



not all existing trucks requiring some treatment would require



each of the treatments indicated to reach each  noise level indicated.



The percentage of trucks indicated in Table 1 to  require each type of



component change is based upon actual experience  of  a company  that has



been extensively engaged in retrofitting trucks to reduce noise emissions.



The average cost per  large multi-axle truck that  requires  treatment  to



meet each level is thus the sum of the percentage of trucks that require



each treatment times  the cost of that treatment,  for each type of



treatment.  The average cost  of bringing noise levels of existing




multi-axle trucks down to 86  dB(A) is thus $114.



     For comparison with the  estimated retrofit costs, Figure 6 shows



the typical costs actually incurred in the retrofit  of over 7,600 Icirge



multi-axle trucks by  that company.  The  agreement is good with  the
                                    36

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              TABLE 1 - ESTIMATED COSTS TO RETROFIT TRUCKS TO VARIOUS
                        NOISE LEVELS (According to SAE J366a)
Noise Level
dBA (? 50'

90

88

86

84

Required
Treatment

Exhaust1

Exhaust
Fan2

Exhaust^
Fan4
IntakeS

Exhaust6
Fan7
Intake5
Engine"

Estimated Cost
Per Item $

50-100

50-100
35

100
80
115

100-200
285-400
115
80-130

% Trucks exceeding
specified noise level
Requiring Pompon p.nf
Change
100%

100%
5%

100%
• 10%
5%

100%
50%
25%
25%

Avg. Cost Per Truck
Requiring Retrofittir

$50 - $100
Total $50 - $100
50 - 100
2 - 2
Total $52 -|102
100
8
6
Total $114
$100 - $200
$143 - $200
$ 29 - $ 29
$ 20 - $ 33
Fotal $292 - $462
1.  Muffler and labor—single or dual system
2.  Replaced fan blade
3.  Mean cost for muffler and labor, plus additional  cost for some
    trucks requiring replacement of flexible tubing,  etc.
4.  Replaced fan blade and added shroud
5.  Average cost of dry element air cleaner with built-in silencer.
6.  Muffler and replacement of feasible pipes—single or dual system
7.  Viscous fan clutch and new fan blade in conjunction with shroud.
    Thermostatically controlled clutch.
8.  Partial engine kit plus installation.
                               37

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PERCENTAGE OF TRUCKS EXCEEDING A GIVEN
NOISE LEVEL DURING TYPICAL HIGHWAY OPERATION —
CALIFORNIA DATA
Noise Level
dBA
% trucks exceeding
Speeds 33 mph and
less
noise level
Speeds greater than
35 mpn
 92

 90

 88

 86

 Bk

 82
 0

 5

 6

12

19

30
 0

10

19

50

78

93

97
                  38

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exception of the costs to achieve a noise level of 84 dB (A).  At this



level, the incurred costs are for a very small number of vehicles and




the estimated costs are  approximate.  Experience in retrofitting



trucks indicates that the noise level of almost all trucks on the road



today can be reduced to an  86 dB(A) level; however, the noise level of




only about 50 percent of existing multi-axle trucks could be brought down to



84 dB(A) using available hardware.  To achieve this level on those trucks on



which it can be achieved, engine enclosures would often be reouirBd.



This type of hardware is not currently available in the large quantities



that  would be required by  an 84 dB(A) standard, nor has it been fully



tested on in-service trucks.  The completion of tests on such hardware



and the  establishment of production distribution systems for large  quan-



tities of enclosures for specific application will require an inestimable



lead time.  The company estimates that from their very limited experience



with engine enclosures in achieving noise  levels of 84 dB(A) that it



would cost about  $950 per truck to bring large multi-axle diesel trucks



down to that level,  if adequate hardware for that purpose were available



and if  the safety and maintenance aspects  of the enclosure configuration



were established.  For application to significant numbers of trucks,



additional lead time would  be required to  establish a production base



and supply system to retrof itters.






"BEST AVATTARLK TECHNOLOGY, TAKING INTO ACCOUNT THE POST OF COMPLIANCE"



     These terms  have been  defined for purposes of this proposed regulation



as follows:
                                   39

-------
          "Best available  technology" is that noise abatement

     technology available  for retrofit application to motor

     carriers that  produce meaningful reduction in the noise

     produced by interstate motor carriers.  "Available"

     is further defined to include:

          1.  Technology applications that have been
             demonstrated and  can be retrofitted on
             existing trucks.

          2.  Technology for  which there will be a production
             capacity to  produce the estimated number
             of parts required in reasonable time 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 opera-
             tional considerations, including maintenance,
             and other pollution control equipment.

          The cost of compliance means the cost of identifying

     what action must be taken  to meet the specified  noise

     emission level, and the  additional cost of operation

     and maintenance.  The cost for  future replacement parts

     was also considered.

     Summarizing the discussion of truck noise other  than the  tire noise leads

to the following major conclusions:

     1.  Nearly all existing  large trucks can be retrofitted to

         achieve a noise level  of 86 dB(A)«  under 35 mph.

     2.  A large proportion of the trucks that presently exceed 84 dB(A)

         under 35 mph could not be brought to this level using current available

         hardware or technology without extreme modifications, e.g.,

         total  encapsulation  or replacement  of the engine.


                                  40

-------
      3.  The costs associated with retrofitting large multi-axle



         diesel trucks  increase greatly between the levels of



         86 dB (A) and 84 dB (A) .



      4.  Large multi-axle diesel trucks constitute the most



         severe interstate motor carrier noise problem.  Any  noise



         standard that  is reasonable  for  them to meet can beassumec3 to




         be reasible for other interstate motor carrier vehicles to




         meet.   It is therefore possible to hold all interstate motor carrier



         vehicles over 10,000 pounds GVWR or GCWR to the standard set



         on the basis of the noisiest trucks for an interim period.  When



         more information is available on feasible noise standards for



         various subcategories of interstate motor carrier vehicles, the



         proposed regulation can be revised to incorporate such information.



      Accordingly, the conclusion can be reached that the noise emission



 level that existing  trucks can be expected to achieve, exclusive of



 tire noise, after the application of the best available  technology,



 taking into account  the cost of compliance,  is 86 dB(A), for speeds



 less than  35 miles per  hour.   Based  on the truck survey  data  from Calif-




ornia in 1965 discussed earlier in this section (see Table 2),  19 percent



of the large multi-axle diesel trucks in operation today will not initially



comply with the noise standard.  Non-diesel trucks and other vehicles



will  generally require  much  less treatment to meet the standard than



 diesel trucks  and,  consequently, will incur much smaller average  costs.



 Most of them meet the proposed standard now,  and those that do not will
                                   41

-------
rarely require more than a new muffler to meet the proposed low speed
standard.
     Since the noise characteristics of large vehicles differ at low
 and high speeds—the propulsion system noise dominating the former and
 the tire noise the  latter—it  is necessary to set different noise standards
 for low and high speed operation so that both major noise sources will
 be covered.  At  speeds greater than 35 miles per  hour, the noise levels
 produced by trucks  complying with the 86 dB(A) low speed standard will
 normally exceed  86  dB(A) because of the increase  in the tire noise
 contribution.  Examination of  the noise distribution of trucks operating
 on the highway—see Figure 3—shows that the same number of trucks that
 exceed 86 dB(A)  at  speeds  less than 35 miles per  hour exceed 90 dB(A) at
 speeds greater than 35 miles per hour.  In most cases, trucks that can
 comply with the  low speed  noise standard can also comply with a 90 dB(A)
 noise  level at high speeds.  Some trucks equipped with the noisier types
 of cross-bar  tires  will  exhibit higher noise levels and would be required
 to install alternative cross-bar or rib tires, particularly on the drive
 axles.  Trucks equipped  with pocket retread tires will normally exceed
 the proposed  regulation  of 90  dB(A) at speeds in  excess of 35 miles per
 hour—see Figure 2. The 90 dB(A) high speed standard will therefore
 effectively remove  this  type of tire from highway use.  It is therefore
                                   42

-------
appropriate to incorporate into the regulation a visual inspection clause



to restrict the use of pocket retread tires.



     In many cases, trucks will exceed the proposed noise standards



because of poorly maintained exhaust systems.  Accordingly, it is con-



sidered that the proposed regulation should contain a clause allowing



for a visual inspection of the exhaust system.
     When heavy trucks are operated at speeds of 35 miles per hour or



less, they are often in urban or suburban areas.  It is during this phase



of their operation that truck noise emissions can have a major impact



on the public due to the large population densities in these areas.



Under certain conditions of highway grade and constant speed less than



35 miles per hour, trucks can be operated in a manner  that will miniinize




exterior noise emissions.  The principal variable in attaining these



lower levels is operator technique.



     Trucks designed or retrofitted to the recommended 35 miles per hour



all-conditions pass-by test level of 86 dB (A), if operated in a quiet



manner,would emit exterior sound levels of 80 dB(A) or less.  As shown



in Figure 9, the percentage of vehicles that could not comply with a



level of 80 dB(A) on level roadways is approximately the same as the



percentage of vehicles not complying with the two recommended noise



emission standards at 86 and 90 dB(A) discussed earlier.
                                   43

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     An  80 dB(A) level does not impose an additional cost to the

 industry above that which is required to meet the other reconmendai noise control

 levels,  but  it does require quiet operation in areas where population

 densities are generally high.


STATIONARY RUN-UP,TEST

     The Federal enforcement of the proposed noise regulation will be

 undertaken by inspectors from the Bureau of MDtor Carrier Safety  (BMCS)

 of the Department of Transportation  (DOT).  Four possible enforcement

 strategies  were considered..   These are:

     !• Enforcement  at the time the owner first receives the vehicle

     2. Enforcement  at random times at the vehicle depot

     3. Enforcement  during normal operation on the highway

     4. Enforcement  at specific roadside locations, such as weigh
         stations.

     Enforcing the noise regulation at the time of initial  (or subsequent)

 sale would not take into consideration that the noise level produced by

 a motor  vehicle may increase with age as a result of poor maintenance or

 improper selection or replacement of parts.  Enforcement at the vehicle

 depots would lead to significant logistic problems due to the wide

 dispersion of depots.  The noise regulation could be enforced by  setting

 up measurement locations alongside major highways and monitoring  the

noise produced by each vehicle as it passes through the site.  This is the

 method adopted by the California Highway Patrol and other enforcement

 agencies who have "curbing" power,  or , the ability to pursue and

apprehend offending operators.  The DOT inspectors do not have this

 power, but they do have the power to inspect vehicles at roadside weighing
                                   44

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stations.  This form of enforcement requires a method of measuring the



noise produced by the vehicle while in the weighing station such that



the noise levels correlate well with those measured for typical opera-



tion on the highway.  Lack of space at the weighing station indicates



that this should be a test conducted with a stationary vehicle.  Such



a stationary test procedure has been developed by the motor vehicle



manufacturers through the Society of Automotive Engineers.  Though the



test procedure has only been documented on 877 trucks, the results




indicate a close relationship with  the SAE J366a test,  and it is considered



acceptable by DOT.  It consists of running the engine from idle to



stabilized governed engine speed with rapid application of the throttle.



The noise level measured is the maximum value observed during the test.



     No such stationary test is recommended for vehicles  that use



engines without engine speed governors (ungoverned engines)  for



the following reasons:



     1.  The operator variability (including tachometer error) in



         achieving horsepower rated rpm.



     2.  Tte variability of manufacturer specified horsepower



         rated rpm.



     3.  The likelihood of catastrophic engine failure when an



         ungoverned engine is rapidly accelerated to such high speeds .



None of these drawbacks exists  for  governed truck engines.  Since it



is the diesels and big gasoline engines that normally produce the highest



noise levels (exclusive of purposefully modified exhaust systems) and
                                  45

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 since these engines are normally equipped with engine speed  governors,
 the fact that this test procedure is limited to such vehicles will not
reduce the effectiveness of the overall regulation.
      The noise  level of a truck measured according to the above stationary
 procedure  is about 2 dB   greater than the noise  level produced in the
 course of  typical acceleration at low speeds  (less than 35 miles; per hour).
 Therefore,  a noise level  of  88 dB(A)  measured according to the stationary
 test procedure  is considered approximately equivalent to a level of
 86  dB(A) measured on the  highway during acceleration at speeds less than
 35  miles per hour.

TIME FOR COMPLIANCE
      In  determining the amount of time  required  for  trucks to apply
 some retrofit solution—if they exceed  the proposed  noise emission
 standards—the  following  factors must be taken into  account:
      1-  The  availability of replacement hardware—mainly mufflers
         and quiet tires.
      2.  The  replacement  cycle for items that need to be replaced .
      In  many cases, the action required to bring a noisy truck into
 compliance with a proposed noise emission regulation would be the
 replacement or  installation  of a suitable muffler.  Replacement mufflers
 are provided by the original equipment manufacturers as well as by the
 replacement equipment manufacturers.   In general,  the  industry is capable
 of  increasing its output  of  mufflers, probably by  a  factor of two,
 because  it has  the additional facilities and material  necessary.
                                   46

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The life of a muffler depends greatly on the actual truck operation, but



is on the order of one to two years.  Therefore, to a first approximation,



one-half of the trucks will install new mufflers every year.



     In contrast, the tire industry is at present striving just to



maintain a sufficient supply for the demands of the trucking companies.



The life of a cross-bar tire as installed on a "line-haul" truck is not



usually greater than 100,000 miles, which corresponds to a tire tread



life of approximately one year.



     Considering all of the information given leads to the conclusion



that the majority of trucks can be modified to comply with the



proposed noise emission standards within one year from promulgation of



the regulation.  It should be noted that the estimated costs for



compliance do not take into account the normal replacement cycle for




mufflers, since such repalceraents are not related to these costs.
                             -47-

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  1000
   900
   800
   700
CO
rH
S  600
8
    500
    400
    300
    200
    100
     0
          estimated
         cost of retrofitting
                         range based on actual
                         cost of retrofitting
                         Total Sanple   7/600  trucks
        a
       94    93
92
91    90
89
88    87    86    85
84
                   Attained Noise Level,  dBA @ 50'
                    (Low Speed, Full Throttle)
      Figure 6,    Estimated and Actual Cost Incurred in Retrofitting
                   Trucks  to Various Noise Levels
                                48

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          DATA SOURCE
          ° CALIFORNIA  (1971)  172 TRACTOR-TRAILERS
                              "OVER 35 MPH"
          A CALIFORNIA  (1371)  145 TRACTOR-TRAILERS
                              "35 MPH OR LESS"
    100
  LU
  _J

(  jj
                                               100
J10
               70        80        90

                   NOISE LEVEL dB (A) AT 50 FT

Figure 7 -  Tractor-Trailer Noise Emission Distributions at 35 mph and over 35 ir

-------
99.8
99.5
99
98
95
M 90
3
0 80
(0
I 70
o
03 50
tn
£ 40
1 30
X
w
w 20
"v
1 10
o
c*= 5
2
1.0
0.5
0.2
0.1
0.05
0.01
8



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\~\
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!


*
DATA SOURCE - i
0 CALIFORNIA (1971) 172 COMBINATION VEHICLES 1 -
A CALIFORNIA (1965) 5,838 DIESEL TRUCKS jj
0 WASHINGTON (1972) 531 TRUCKS, jl
3 OR MORE AXLES .J
A NEW JERSEY (1972) 1000 TRUCKS 1
3 OR MORE AXLES J
SPEED ZONES OVER 35 MPH |

\
^J


















0 82 84



•

K
\.R\
1 \~\V~\











^





^Sk









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^









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v^
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^§x
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i

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I
i
^3x"
r\

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\
86 68 90 92 94 96 98
                      Noise Level dBA at 50 Feet


Figure 8«.  Truck  Noise Emission Road Side  Survey Data for Soeeds Ov^er
           35 nph.


                        50

-------
            A CALIFORNIA (1971) 105 COMBINATION VEHICLES

               "LEVEL ROADWAY" (CORRECTED)

            SPEED ZONES 35 MPH OR LESS
  £3
    9
1UU
50
0
6
j i i i ri ! i s
~! 1 I I 1.1.!.!.!.
I'M.ri Jill
\
V
*<
1 I 1 I ' I M i
i II I I I I I 1
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i i 1 1 I 1 I ) I
1 ! 1 I 1.1 ! I !.
1 ! I ! I 1 1 i L_j
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0 70 80 90 TOO 110
                 ENFORCEMENT LIMIT,  dB(A) AT 50 FT
FIGURE 9.  Tractor-Trailer Noise Emission Distribution at 35 mph
         or Less on Level Roadways.
                            51

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                    Section  7


        ECONOMIC  IMPACT OF THE PROPOSED REGULATIONS



 DIRECT RETROFIT  COST



       In  order  to relate   individual truck



 retrofit  costs  to the  total  impact on the industry,  the



 number of trucks  engaged  in  interstate commerce  over



 10,000 pounds GVWR must be determined.  There  is no



 direct method for making  this determination.   A  reasoned



 judgement was made based  on  truck population statistics,



 industry  information,  and inputs to the Advance  Notice



 of  Proposed Rule  Making Dofefeet that approximately



 1 million trucks  over  10,000 Ib GVWR or GCWR were engaged  in


                    55 54   12
 interstate commerce.   '    '   '



       As  discussed in  Section 6, the primary impact  of  the



 proposed  regulation will  be  on large multiaxle trucks,



 which are primarily powered  by diesel engines.  Section  6



 shows  an  estimated average cost of $114 (with  a  range of $50



 to  $200)  to bring into compliance those trucks with  3 or more



 axles  that are  not presently in compliance with  the  proposed



 regulation.  Figure 8, a  survey of diesel



 trucks in California  in 1965 (before that  state  had  any



 noise regulation   that might influence  the  data),  shows  that



 19% of those trucks would be in  violation  of the proposed



 standard.  Data from  New  Jersey  and Washington (figure



 8), support this  figure of  about 19% of  multi-axle diesel



trucks that would  be in violation of the proposed standard.



(See Appendix A for data  on the percentage of  vehicles
                         52

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that might  initially be in violation of the proposed



standards that"  have been accumulated for EPA since



the date of publication of the proposed regulation).



     The $114 average cost per truck shown in Section 6



is for those approximately 19% of the trucks (3 axles



and over) that are expected initially to be in violation



of the proposed standard.  The mean direct retrofit cost



to the industry is therefore $22 million dollars, with



a range of $10 to $38 million dollars.



     For a truck running 50,000 revenue miles per year,



a $114 retrofit cost represents an increased expense of




$0.002    Per revenue mile when amortezed over a single



year.  When this increase is compared with current



average expenses of $1.20 per revenue mile (see Section



2), it can be seen that cost is not an obstacle to



lower noise emission standards.



OTHER COST CONSIDERATIONS



     Additional costs include loss of revenue resulting



from trucks being out of service during retrofit.  The



installation of a suitable muffler may increase the back



pressure on the engine and in turn increase the fuel



consumption.  Considering the wide variety of mufflers



available for different types of engines,  a significant



increase in back pressure is avoidable.
                         53

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     There are also some factors that reduce the



total cost.  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, the difference in



cost being in the range of a few dollars.



     Secondly, for those trucks requiring installations



of a more efficient fan, the amount of engine power wasted



in driving the fan will be reduced.  Standard diesel fans



typically consume 15-25 horsepower.      In particular,



the addition of a thermostatically controlled fan clutch



can decrease the 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.
                       54

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                        Section 8




        ENVIRONMENTAL IMPACT OF PROPOSED REGULATION



POSITIVE EFFECTS



     The proposed regulation impacts directly on those



trucks that presently make the most noise and requires that



they be quieted to levels that are feasible from a cost and



technology standpoint within one year of final promulgation.



The principal noise reduction will be of the intrusive "noise



peaks", which have been widely acknowledged as more objec-



tionable to people than much lower levels of continous noise.



These peaks can be 12 dB or more above ambient highway noise



level.    The benefit of noise reduction is to be realized in



1 year or less.



     A significant increase in truck fuel economy will also



be realized for those trucks that require installation of



more efficient fans to meet the proposed noise emission



standard.  As described in Section 7, thermostatically controlled



fan clutches that engage the fan only on engine cooling



demand can decrease fuel consumption throughout the life of



the truck.






NEGATIVE EFFECTS




     There may be a slight increase in the number of older



trucks retired from service? and that would therefore suddenly



increase the solid waste disposal problem by the number of
                            55

-------
trucks scrapped.  Following this, the scrappage rate would



decrease as a result of the younger population of trucks.



However, a small net increase on total trucks scrapped would



be obtained - an increase related to the number of truck years



lost from service.  Because the net increase in scrappage



would be small, and because of the ready market for steel,



adverse environmental effects would be minimal.




     There will be no anticipated increase in scrap tires



resulting from these regulations.  The pocket tread design



tire that the regulation excludes from highway use is not in



wide use, and those currently installed and in stock would



wear out prior to the effective date of the regulation.  In



some installations of a quieter muffler, there may be an



increase in back pressure on the engine and a resulting



decrease in fuel economy.  As discussed in Section 6, a



significant increase in back pressure is avoidable in almost



all cases by a muffler matched to a particular engine.
                          56

-------
                         APPENDIX A



             TRUCK NOISE EMISSION DATA AND ANALYSIS






      Sijbsequent to the issuance of the proposed regulation, a substantial



additional body of recent vehicle noise survey data has now been analyzed.



This body of data was obtained in 10 states, in which approximately



39 percent of all U.S. trucks and buses are registered.  For 9* of



these 10 states, the data permitted an assessment of the percentages of



various types of trucks that would exceed the proposed standards.  From



the analysis, it was concluded that:



1.  An average of 23 percent of all observed trucks above 10,000 pounds



GVWR or QCWR exceeded the proposed standards (Table A-l).



2.  The mean percentage of observed trucks exceeding the proposed



standards varied significantly by type of truck: 1.9 percent for two-



axle straight trucks, 10.8 percent for three-axle combination trucks,



15.0 percent for four-axle combination trucks and 36.1% for 5-axle



combination trucks  (Table A-2).



3.  The range of percentages of trucks observed in the nine states



that exceeded the proposed limits was substantial: 0.6 to 3.5 percent



for two-axle straight trucks above 10,000 pounds GVWR, 1.2 to 26.0



percent for three-axle straight trucks,
      *California, Colorado, Illinois, Kentucky, Maryland, New Jersey,



New York, Pennsylvania, Texas



      **The average of 23.1 percent calculated in Table A-l is an



arithmetic mean of percentages exceeding the proposed standards in



various states, unweighted by sample size.



                       -57-

-------
   1.0 to 26.0 percent for three-axle combination trucks,



   3.0 to 26.0 percent for four-axle conbination trucks,



   and 7.0 to 74.0 percent for five-axle conbination trucks (Table A-2)



4j According to the 1972 Census of Transportation - Truck



   Inventory and Use Survey (Department of Commerce, Bureau



   of the Census)/the total population of registered trucks



   above 10,000 Ibs. GVWR or GCWR is distributed approximately



   as follows:



        72.1 percent two-axle straight trucks,



        10.3 percent three-axle straight trucks,



        2.4 percent three-axle conbination trucks,



        5.5 percent four-axle conbination trucks,



        8.0 percent five-axle conbination trucks, and



        1.7 percent other or unspecified types.



 9. Multiplying these percentages by the mean percentage of



   each type exceeding the proposed standards reveals that



   approximately 7 percent of all registered trucks above



   10,000 Ibs. GVWR or GCWR exceed the proposed standards  (Table A-3).



61 The apparent discrepancy between the 23 percent of trucks



   observed on the road and the 7 percent of all registered



   trucks above 10,000 Ibs. GVWR or GCWR that exceed the proposed



   standards results from the fact that conbination trucks



   travel many more road miles per vehicle per year than straight
                         -58-

-------
     trucks do.   For example,  five-axle examination trucks

     constitute  approximately  50 percent *   of the trucks observed

     on a typical interstate highway,  even though they represent

     only 8 percent of all registered trucks in the weight class

     under consideration.
     3For the nine of ten States represented in the new data base where
the data allow for a breakdown by axle category, of the 6,875 total
trucks over 10,000 pounds GVWIV'GCWR, 4,098 or 59.5 percent were 5-axle
trucks.

                           -59-

-------
                                  Table A-l

          SUMMARY OATH FOR ALL TRUCKS ABOVE 10, "D00 LBS GVWR OR GCWR
               Mean Noise                           % Ab°Yg.
State  Source    Level    Mean Speed   90.0 dB(A)   91.0  dB(A)   92.0 dB(A)

 CA     W.L.   85.4dB(A)(a)   -          5.0%         3.0%          1.5%
 CO     BBN    84.6           51.7mph    10.0          4.5          2.0
 IL     BBN    89.1           57.2       42.0         21.0         15.0
 KY     BBN    88.8           61.3       40.0         30.0         21.0
 MD    Md.DOT  88.1           -         30;0         21.0         14.5
 NJ     BBN    87.2           56.5       20.0         12.0          7.0
 NY     BBN    88.8           60.0       43.0         30.0         18.0
 PA     W.L.   86.2 (a)        -         13.0          8.0          5.0
 TX     BBN    83.7           56.1       12.5          7.5          4.0
 WA    WA-72   86.6 (a)   ,     -         16.0          9.0          6.0
mean percentage exceeding given noise  level:

                                        23.1%        14.6%          9.4%
(a)  median
                                 -60-

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                                  Table A-2

           SUMMARY OF TRUCK NOISE EMISSIONS BY TYPE OF TRUCK

               Mean Noise                          % Above
State  Sourc^   Level     Mean Speed  90.0 dB(A)   91.0 dB(A)  92.0 dB(A

 CA     W.L.  ^81.0dB(A)(a)    -           1.2%        0.6%        0.3%
. CO     BBN    80.4          50.9mph     1.9          1.0         0.5
 IL     BBN    83.1          55.7        1.0          0.3         0.1
 KY     BBN    82.9          57.7        1.0          0.3         0.1
- MD    Md.DOT  83.9           -           3.5          1.6         0.8
 NJ     BBN    82.3          55.7        0.6          0.2         0.1
 NY     BBN    85.1          59.4        6.0          3.3         1.9
 PA     W.L.   81.2(a)         -           0.9          0.4         0.2
 TX     BBN    78.6          54.6        0.6          0.3         0.1

mean percentage exceeding given
noise  level:                              1.9%        0.9%        0.5%


                          3 AXLE STRAIGHT TRUCK


 CA     W.L.   85.2(a)(b)     -           8.0          4.0         2.0
 CO ^   BBN    84.1          47.7        1.2          0.4         0.1
 IL     BBN    85.8          54.5        9.0          4.5         2.0
 KY     BBN    87.7          59.9         *           *           *
 MD    Md.DOT  87.5           -           *           *           *
 NJ     BBN    84.7          57.4         *           *           *
 NY     W.L.   88.0(a)(b)     -         26.0         17.0        11.0
 PA     W.L.   84.5(a)(b)     -          2.0          0.9         0.3
 TX     BBN    84.8          50.6         *           *           *

mean percentage exceeding given
noise  level:                              9.3%        5.4%        2.7%
                          3 AXLE COMBINATION TRUCK

  CA     W.L.    85.2(a)(b)     -          8.0         4.0          2.0
  CO     BBN    83.8          51.9         *           *            *
  IL     BBN    86.0          55.7         *           *            *  •
  KY     BBN    87.8          59.0         *           *            *
  MD    Md.DOT  86.6           -         17.0        11.0          7.0
  NJ     BBN    85.7          57.2        1.0         0.3          0.1
  NY     W.L.    88.0(a)(b)     -         26.0        17.0         11.0
  PA     W.L.    84.5(a)(b)     -          2.0         0.9          0.3
  TX     BBN    83.0          56.5         *           *            *

mean  percentage exceeding given
noise level:                             10.8%        6.6%         4.1%


 (a) median
 (b) all 3 axle trucks
  * insufficient data

                                    -61-

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                                Table A-2 (Continued)
 State  Source
          4 AXLE COMBINATION TRUCK
Mean Noise
  Level
% Above

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

wean speed
49.0
55.4
61.0
57.7
58.8
56.4

90.0 dB(A)
3.0%
9.0
22.0
24.0
26.0
11.0
26.0
.0
4 5

91.0 dB(A)
2.0%
4.0
15.0
13.0
19.0
6.0
13.0
3.5
. 0

2. U dB (A)
1.2%
1.4 '
9.0
6.0
12.5
2.5
7.0
2.0
1.0
 mean percentage exceeding
 noise level:
                                         15.0%
                                      8.6%
                                                                   4.7%
                          5 AXLE COMBINATION TRUCK
CA ^
CO
IL
KY
MD
NJ
NY
PA
TX
W.L.
BBN
BBN
BBN
Md.DOT
BBN
BBN
W.L.
BBN
85.9(a)
87.0
90.2
90.6
89.7
88.3
91.2
87. 6 (a)
87.5
53.7
57.7
62.6
58.7
61.6
57.9
7.0
18.0
-51.0
56.0
42.0
32.0
74.0
22.0
23.0
mean percentage exceeding given
noise level:
                                         36.1%
                                                      3.5
                                                      8.0
                                                     38.0
                                                     42.0
                                                     31.0
                                                     20.0
                                                     56.0
                                                     14.0
                                                     14.0
                                    24.9%
                                                  1.6
                                                  3.0
                                                 26.0
                                                 30.0
                                                 21.0
                                                 12.0
                                                 34.0
                                                  9.0
                                                  8.0
                                                                 16.0%
(a)  median
                               -62-

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                                Table -A-3
                    ESTIMATED NUMBER OF TRUCKS AFFECTED
2 axle straight truck
3 axle straight truck
3 axle combination
4 axle combination
5 axle combination
All other (a)
% of all
trucks above
10,000 Ibs

   72.1%
   10.3
    2.4
    5.5
    8.0
    1.7
% of type
exceeding
90.0 dB(A)

   1.9%
   9.3
  10.8
  15.0
  36.1
  36.l(b)
% of all trucks
above 10,000 Ibs
affected	

     1.37%
     0.96
     0.26
     0.83
     2.90
     0.61
2 axle straight truck
3 axle straight truck
3 axle combination
4 axle combination
5 axle combination
All other (a)
% of all
trucks above
10,000 Ibs

   72.1%
   10.3
    2.4
    5.5
    8.0
    1.7
% of type
exceeding
91.0 dB(A)

   0.9%
   5.4
   6.6
   8.6
  24.9
  24.9(b)
% of all trucks
above 10,000 Ibs
affected	

     0.65%
     0.56
     0.16
     0.47
     1.99
     0.42
     4.25%
2 axle straight truck
3 axle straight truck
3 axle combination
4 axle combination
5 axle combination
All other (a)
% of all
trucks above
10,000 Ibs

   72.1%
   10.3
    2.4
    5.5
    8.0
    1.7
% of type
exceeding
92.0 dB(A)

   0.5%
   2.7
   4.1
   4.7
  16.0
  16.0(b)
                                                      % of  all  trucks
                                                      above 10,000  Ibs
                                                      affected
 (a)   "All  other"  includes  straight truck with trailer, combinations
      with  6  or more axles,  and unspecified combinations.

 (b)   No data available.  Percentages exceeding various noise
      levels  assumed to be  the same as for 5 axle combinations.
                                -63-

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                          References



1,   American Trucking. Trends, 1972, by the American Trucking



Association, Inc., Washington, D.C.



2.  1973 Motor Truck Facts, by the Motor Vehicle Manufacturer



Association, Detroit, Michigan



3.  Advance Notice of Proposed Rule Making, Federal Register,



Vol. 33, No. 21, P. 3087, Feb. 1, 1971



4.  EPA Public Hearing on Noise Abatement and Control-



Manufacturing and Transportation Noise, Chicago, Illinois, July



28-29, 1971



5.  "Transportation Noise and Noise from Equipment Powered by



Internal Combustion Engines," U.S. Environmental Protection Agency,



Report NTID 300-13, Dec. 31, 1971



6.  "Use of Motor Vehicle Noise Measuring Instruments,"



California Highway Patrol Report, 1965



7.  Foss, R.N., "Vehicle Noise Study - Final Report," Applied



Physics Laboratory, University of Washington, Report for Wash-



ington State Highway Commission, Department of Highway, June, 1972



8.  Unpublished data, Bolt, Beranek and Newman



9.  "California's Experience in Vehicle Noise Enforcement,"



California Highway Patrol  (Exhibit G, ONAC Docket M07O)



10 .  Personal Communication with W.H. Close, Department of



Transportation
                             64

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11.  Unpublished data, Bolt, Beranek and Newman, Memorandum to



EPA, June 1, 1973



12.  "Community Noise" U.S. Environmental Protection Agency, Report



NTID 300-3, Dec. 31, 1971, p.4.



13.  Ibid., p.5



14.  "Exterior Sound Level for Heavy Trucks and Buses -



Recommended Practice SAE J366a," Society of Automotive Engineers,



New York, New York, 1971



15.  "Vehicle Noise Measurement," California Administrative



Code, Title 13, Chapter 2, Subchapter 4, Article 10, February



1968



16-  "Measurement of Noise Emitted by Vehicles," 3362, International



Organization for Standardization, 1964.



17*  "Research on Highway Noise Measurement Sites," Wyle Labor-



atories Report for California Highway Patrol, March 1972



18.  Op Cit., 1973 Motor Truck Facts



19. Report to the President and Congress on Noise, February,



1972, p.p. 2-73



20.  Op Cit, NTID 300.3 pp A-S, A-7



21. Effects of Noise on People, NTID 300.7



22.  Op Cit., NTID 300.13 p. 92-95



23.  Op Cit., NTID 300.13 p. 92-93



24.  "Truck Noise I - Peak A - Weighted Sound Levels Due to



Truck Tires," National Bureau of Standards Report by Department



of Transportation, Report No. OST-ONA 71-9, Sept., 1970






                             65

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25. Op Cit., 1973 Motor Truck Facts



26. Op Cit., 1973 Motor Truck Facts



27. Op Cit., NTID 300.13 pp 96-106



28.  Op Cit., 1973 Motor Truck Facts



29-  Op Cit., NTID 300.13, p. 102



30. Alexandra, A., "Motor Vehicle Noise,"  O.E.C.D.  Report, Novem-



ber, 1971



31.  Op Cit., "Truck Noise I11 Sept. 1970



32- Personal communication with W.H. Close,  Department of



Transportation



33'  Op Cit., DOT Report No. OST-ONA 71-9, p.  3-4



34-  Op Cit., NTID 300.13, P. 94



35.  Op Cit., NTID 300.13, P. 100




36- "Diesel Exhaust and Air Intake Noise," Stemco Manufacturing



Company for Department of Transportation,  Report No.  DOT-TSC-OST-73,



March 1973.



37.  Data from Service Engine Company, Cicero,  Illinois



38.  Wyle Laboratories personal cortnunication with three major




muffler manufacturers  (Donaldson Company, Riker, and Stemcoj.



39.  Op Cit., NTID 300.13, P. 103



40.  Wyle Laboratories, personal communication with Flesc-A-Lite



Corp., Tacoma, Washington



41.  Wyle Laboratories, personal communication with Advanced



Products Group, White Motor Company, Torrance,  California
                              66

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42.  Shipe, M.D.,  "Operating Principles of the Schwitzer Viscous
Fan Drive," Schwitzer  Division of the Wallace-Murray  Corp.,
Indianapolis, Indiana,  March, 1971
43.  Published  literature from Schwitzer Division  of  the Wallace-
Murray Corp., Indianapolis,  Indiana
44.  Op Cit., NTID 300.13,  P. 104
45.  Law, R.M.,  "Diesel Engine and Highway Truck Noise Reduction,"
Society of Automotive  Engineers  (SAE) Report  730240,  Jan.,  1973
46.  Literature  from Donaldson Company, Minneapolis,  Minnesota
47.  Davisson,  J-A.,  "Design and Application  of Commercial  Type
Tires," SAE Paper  SP 344, Jan., 1969
48.  Wik, T.R.,  and Miller,  R.F., Mechanisms  of Tire  Sound
Generation,"  SAE Paper SP373, Oct., 1972
49.  Wyle Laboratories, personal communication with major
tire companies
50.  Wyle Laboratories personal communication with W.H. Close,
Department of Transportation
51.  Op Cit., DOT  Report OST-ONA 71-9, P. 42
52.  Op Cit., NTID 300.13 P. 7
53.  Personal communication with Ben Sharp of Wyle Laboratories
54.  1972 Census of transportation -Truck Inventory and Use
Survey, Dept. of Commerce,  Bureau of the Census
55.  Response  from American Trucking Association, April 2, 1973, Docket
     Serial No. M042

56.  Wyle Laboratories communications with the Schwitzer Division of
     Wallace-Murray Corporation  and the Flex-a-lite Corporation, 1973.
                                67

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57.  Bolt, Beranek and Newman, Inc.  Report No.  2563,  The Cost of Quieting



     Heavy Cab-Over Engine Diesel Tractors, July 1973




58.  Transportation Noise and its Control, p. 10, DOT publication



     P5630.1, June 1972.



59.  Op.  cit., p. 96, p. 101, NTID 300.13.
                                      68

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