550/9-77-356
HIGHWAY NOISE IMPACT
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May 1977
P
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Office of Noise Abatement and Control
U.S. Environmental Protection Agency
Washington, D.C. 20460
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TECHNICAL REPORT DATA
(Please read ! w,iictlons on the reverse before completing)
L 7 RTN 12. 3. RECIPIENT’S ACCESSIO NO.
4. TITLE AND SUBTITLE
A Manual for the Review of Highway Noise Impact
5. R ORT
MaY 1
ORGANIZATION CODE
6. PERFORMING
NO.
7. AUTHOR(S)
Ben H. Sharp, Kenneth J. Plotkin, Patrick K. Glenn,
Robert M. Slone, Jr.
8. PERFORMING ORGANIZATION
10. PROGRAM ELEMENT NO.
. PERFORMING ORGANIZATION NAME AND ADDRESS
Wyle Laboratories/Wyle Research
2361 Jefferson Davis Highway, Suite 404
Arlington, Virginia 22202
11. CONTRACT/GRANT NO.
68—01—3514
PERIOD COVERED
12. SPONSORING AGENCY NAME AND ADDRESS
U.S. Environmental Protection Agency
Office of Noise Abatement and Control
13. TYPE OF REPORT
Final
SPONSORING AGENCY CODE
1921 Jefferson Davis Highway
rI;rlc3fe n’ Virginia 22202
16. SUPPLEMENTARY NOTES
1$. ABSTRACT
A manual has been prepared which presents a procedure for reviewing noise impact of
proposed highway projects. The manual reviews Federal Highway Administration policy for noise
Impact, and includes specific steps for reviewing environmental impact statements and noise study
reports prepared for proposed highway projects. The noise policy of the Department of Housing and
Urban Development and noise levels identified by the Environmental Protection Agency are also
reviewed, so that a complete assessment of the impact of expected noise may be made. A noise
prediction model, consisting of charts, nomograms, and simple equations, is presented so to enabll
an independent check of predicted levels presented in an EIS. The noise model (which includes
barriers) is itself suitable for predicting roadside noise levels.
7. KEY WORDS AND DOCUMENT ANALYSIS
DESCRIPTORS
b.IDENTIFIERS/OPEN ENDED TERMS
C. Field/Group
Highway noise
Environmental impact statements
Environmental noise
Noise models
21. NO. OF GES —
18. DISTATBUTION STATEMENT
Unflmited
19. SECURITY CLASS (This Reportj
Unclassified —
20. SECURITY CLASS (This page)
6
22. PRICE
Unclassified
EPA Form 22201 ($-73)
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550/9-77-356
A MANUAL FOR THE REVIEW OF
HIGHWAY NOISE IMPACT
MAY 1977
U.S. Environmental Protection Agency
Office of Noise Abatement and Control
Arlington, Virginia 22202
This report has been approved for general availability. This report does not
constitute a standard, specification, or regulation.
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TABLE OF CONTENTS
4.3
4.4
APPENDIX A
APPENDIX B
APPENDIX C
APPENDIX D
Page
• . . 1
• . • 3
• . S 3
• . S 7
• • . 10
• . . 10
• • . 17
• . . 19
• . . 21
• . . 23
• . . 23
• . . 27
• . . 28
• . . 29
• S • . 31
• . • . 32
• . . . Al
• I S • Bi
• . • S Cl
• . .D1
1.0 INTRODUCTION . . . . . . .
2.0 THE REVIEW OF ENVIRONMENTAL IMPACT STATEMENTS
2. 1 Review of Input Data . . . .
2.2 Check the Noise Levels Presented in the EIS
3.0 ASSESSMENT OF NOISE IMPACT. . .
3.1 FHWA Noise Standards . . . .
3.2 HUD Bufiding and Development Site Noise Standards
3.3 EPA Identified Levels. . . . .
3.4 Land—Use Compatibihty Guide . • .
4.0 APPROACHES TO NOISE CONTROL . .
4.1 Reduction at the Source . . . . •
4.2 Noise Control in Highway Planning and Design
4.2.1
4.2.2
Barriers. . .
Noise Reduction at the Receiver —
Modifications . •
• •
Dwelling
I I
Land Use . • . • . •
Evaluation of Proposed Measures .
Highway Noise Nomogram Procedure
Barrier Nomogram Procedure . •
Computerized Highway Noise Models
The Effect of Motor Vehicle Noise Regulations On
Highway Noise Levels ,. • •
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1.0 INTRODUCTION
More people in this country are exposed to noise from highways than from any
other single source of noise. It is not surprising, therefore, that adverse impact from
highway noise is of major concern to land—use planners, regulatory agencies, and
impacted or potentially impacted persons. In order to gauge the adverse impact of
noise and limit its encroachment, federal policies now require that an environmental
impact statement (EIS) be prepared for proposed highway construction and for significant
changes in intended use of existing highway systems. The noise section required in an
environmental impact statement must quantify the existing noise climate, define the
additional noise exposure associated with the proposed alternatives, estimate the impact
resulting from the additional noise exposure,and demonstrate that all reasonable measures
have been taken to minimize this impact. For reasons of conciseness and format, an
EIS often contains only major conclusions and data summaries with regard to noise. In
such cases, complete supporting data and documentation are contained in a separate
noise study report. This information s required for a comprehensive evaluation of the
noise section of an EIS. Therefore, within the context of this review manual, the
terminology “environmental impact statement” will be taken to include the noise study
report .
It should also be noted that an EIS is rarely devoted to noise alone. The noise
section often utilizes data presented in other sections. Within the context of this review
manual, “noise section of an EISA’ will be taken to include data presented elsewhere in
the EIS, but utilized in the section specifically dealing with noise.
The evaluation of an environmental noise impact assessment for proposed or
existing highways can be complicated and should be performed by means of a uniform
methodology to ensure that all necessary concerns are consistently addressed. This
manual provides the user with the methodological approach necessary for the review
of environmental impact statements for highway noise and for evaluating the effective—
ness of further actions that may be necessary in the highway design.
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The underlying philosophy evident throughout this manual is one of satisfying
local needs for noise abatement rather than merely ensuring compliance with fixed noise
standards. This reflects the federal policy on highway noise and ensures that noise abate-
ment measures are consistent with local social, economic and environmenta! considera—
tions. Moreover, it is stressed that federal policies relating to housing development and
overall community noise control must be considered together with that relating solely to
highway noise.
The manual itself has been designed so that it can be used by people not
necessarily trained in the field of acoustics. It does assume that the reader is familiar
with some of the terminology, but does not require computational capability other than
the use of char1 , tables and ncmograms,
The manual is divided into three main parts. Section 2 contains the step-by—step
approach to be followed in the review of an EIS; Section 3 describes methods for
assessing the mpact of highway noise; and Section 4 introduces available methods of
noise abatement that should be considered in highway design. Also included is a method
for independently checking the noise level computations using a series of simple
nomograms.
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20 THE REVIEW OF ENVIRONMENTAL IMPACT STATEMENTS
This section of the manual describes the procedure for reviewing an EIS prepared
specifically for a highway project. The project may involve noise control for an existing
highway or it may consist of the construction or reconstruction of a section of hi iway.
The purpose of the review procedure is to deteimine the adequacy of both the noise impact
predictions and the proposed measures for noise abatement. The major steps in the pro-
cedure are as follows:
• Review and evaluate the data used.
• Check the predicted noise levels by means of an independent
calculation.
• Assess the predicted noise impact.
• Evaluate the proposed noise abatement measures.
• Identify additional abatement measures that might be required or might
be desirable.
• Make recommendations for action required.
The details involved in each step of the procedure are described in the following
sections.
2 • I Review of Input Data
To a large extent, the accuracy of the noise predictions will depend on the validity
of the data used in the calculations. It is necessary as a first step to review the
data used In the preparation of the ElS. The approach towards the review should be
critical and should attempt to answer the following types of questions:
• Is the source of the data identified, and is that source reputable?
• Which portion (if any) of the data is based upon forecasts, and what are the
assumptions used in such forecasts?
• Was data requested from all local transportation, planning and housing
agencies — in other words, have all local future plans been considered?
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The input data required for an assessment of an EIS are as follows:
Definition of the Highway
The highway data used in the calculation of highway noise levels are as follows:
• The width of the roadway
• The number of lanes in each direction
• The width of the median strip
• Road grade
• Elevation of the roadway
• Location of entrance and exit ramps
• Posted speed limits for automobiles and trucks
Definition of Local Topography
This infomiation can be provided in a variety of fomis ranging from aerial
photographs and topographical maps of the area to cross-iections of the local terrain.
The essential data to be provided under this heading includes changes of ground elevation
over the study area, and location and height of natural or man-made perturbations of
the terrain which may seive as barriers to acoustic propagation. Where there are
barriers, the required information is as follows:
• The height of the barrier top above the roadway
• The length of the barrier
• The distance from the highway to the barrier
• The distance from the barrier to the receiver
• The elevation of the receiver relative to the highway
Traffic Flow
Traffic data are a necessary input to calculate noise levels associated with the
operation of the highway. Current traffic volume and vehicle mix data are required to
estimate the noise impact of existing highways or to verify noise level measurements.
Future traffic data are similarly required to calculate noise levels assocated with
future operation of the highway. The specific data required are as follows:
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• Present Day:
a. Volume (total vehicles/hour)
b. Mix (percent trucks)
c. Speed
• Design Year:
a. Volume
b. Mix
c. Speed
Present—day traffic data wi II consist of measured traffic F low. These data are
maintained by state and local highway authorities. Estimates of future traffic for the
design year, a fime generally considered to be 10 to 20 years after construction, will
consist of estimates provided by the state and federal highway authorities. Sources and
assumptions for these data will be required.
Land-Use Data
• Present—Day Land—Use Data : In order to evaluate the importance of the
noise levels predicted in the evaluation of an EIS, information on land use
within the study area is necessary. This information may be acquired through
aerial photographs, examination of the local zoning codes applicable to the
study area, from U.S. Census Bureau data, or from a visual examination of
the study area. Since these data are to represent present—day conditions,
zoning information must be used with discretion — undevelcped land will
have no present—day noise impact associated with it, except, of course, for
the case of parks or public access land used for recreational purposes. It
is convenient to present land—use data for parcels of land coinciding with
the local zoning system. The specific data required for each land parcel
are as follows:
— Area
— Frontage length along highway
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— Depth from highway
— Zoning
— Building type
— Population density (where applicable)
— Distance to nearest dwelling
— Height of dwellings
Examples of land-use input data are shown below:
a) Land Parcel A, consisting of 4.86 square miles, fronting the proposed
new highway route is used (and zoned) for multi—family apartments,
with an average population density of 287 persons per square mile.
This parcel has 1500 feet frontage on the proposed new highway route
and the dwelling structures aré’evenly distributed along this frontage,
average 225 feet from the highway route, with the nearest dwelling
57 feet from the highway.
b) Land Parcel B, consisting of 2.5 square miles, is used for industrial
manufacturing and is zoned For heavy industry. This parcel is adjacent
to the proposed route, spanning 1.4 miles of frontage with an average
depth of 1.8 miles. No residential dwellings are located on this tract,
which is used by seven manufacturing concerns.
c) Land Parcel C, consisting of 7.6 square miles, is used, (and zoned) for
single—family residential purposes. This tract. has an average depth of
350 feet from the proposed highway route, with the nearest house 45 feet
from the highway, and extends alàng 4.7 miles of frontage. Tract C has
an average population density of 98 persons per square mile, according
to the latest census survey. Houses are one— or two—stories high.
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• Projected Fulure Land-Use Data : The projected land-use patterns throughout
the study area are based upon present—day demands for various categories of
land, as well as projected growth in and near the study area. These projec—
tions are provided by land—use planners, and this data will routinely be
provided in an EIS. This data allows the noise standards of Section 3.0 to
be applied to specific tracts within the study area for evaluation of the future
noise impact, as indicated by the future noise level predictions.
2.2 Check the Noise Levels Presented in the EIS
The next step in the procedure is to assess the validity of the noise levels given
in the EIS. In the case of an existing highway, these levels may represent measurements
or estimates of highway noise. For a proposed highway, these levels will have to be
predicted, but meosurements of the existing noise levels may be provided.
Measured Noise Levels
Measured noise data are subject to a number of errors which may be introduced at
any stage between the acquisition and presentation. The following factors should be
considered in the assessment of such data.
• The data must have been taken during a period which may be validly
adjusted to design hour conditions. Adjustments for volume may be applied,
provided speed and traffic. mix are similar to those for the design hour.
• Traffic (total volume and number of trucks) must be counted during the
measurement period.
• Full details of the measurements should be provided, including the following:
— Date and time
— Traffic flow and mix
— Duration of measurements
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— Measurement locations
— Site descriptions
— Presence of nearby reflecting obstacles
Weather conditions
— Equipment used
— Sampling rate
— Presence of other noise sources
— Calibration sequence
If the conditions appear suspect, then the persons involved in the measurement
should be contacted, or the site should be examined. The data supplied should
be reviewed critically to provide answers to the following questions:
— What was the rationale for selecting the measurement locations?
— Are there sufficient measurements to adequately define the noise environment?
— Were the noise levels influenced by nearby buildings, unusual sources
of noise, changes in the weather, etc.?
• The traffic conditions should be carefully checked to ensure that they were
unaffected by temporary local events, such as sports meetings, accidents,
route closure, or construction. Existing traffic data can usually be obtained
from the local or State Department of Highways or its equivalent.
In all cases, measured highway noise levels should be checked by comparison to
levels predicted, using the Nomogram Method described in detail in Appendix A. There
is no general method forpredicting the background noise levelsexistingpriortoh;ghway con-
struction and so the assessment must be made solely on the adequacy of the description of
the measurement procedure.
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Predicted Noise Levels
The predicted noise levels presented in the EIS should always be checked for
accuracy. The procedure is as follows:
1. Perform a detailed analysis of the noise levels using the Nomogram Procedure
of Appendix A. If the site is very complex then it may be necessary to use
one of the computer prediction models described in Appendix C. In the
EIS, noise levels should be provided for every section of the highway
which may be considered “different” in terms of the factors described in
Section 2.1. If it is not possible to estimate noise levels at points not
analyzed by reasonable interpolation from levels provided, then not
enough points have been analyzed. In some cases, the noise levels at
additional locations may be required for a full assessment.
2. If the predicted levels differ from those presented in 4 ie EIS, proceed to
Step 3. Otherwise, proceed to Section 3.0.
3. Identify and attempt to resolve any discrepancies between the predicted
levels and those presented in the EIS. This may require contact with the
person responsible for the preparation of the EIS and use of the data in
Appendix C which show differences to be expected from using alternative
prediction models and alternative assumptions.
4. Proceed to Section 3.0.
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3.0 ASSESSMENT OF NOISE IMPACT
Noise impact can be expected under either of the following two conditions;
• If the noise levels approach or exceed the noise standards given in Table 1.
• If the noise levels are substantially higher than the existing levels, even
if they are below the standards given in Table 1.
It is important to recognize that noise impact can occur for this second condition ,
Therefore, all EIS reviews should include an assessment of whether abatement measures
need to be considered, even f the standards of Table 1 are safisfied,
The evaluation of noise levels in areas adjacent to highways should be under-
taken with a full knowledge of the guidelines laid down by various federal agencies.
The FHWA has developed highway noise standards to minimize adverse noise impacts
in the location and design of highways. HUD has adopted a policy that incorporates
interim noise standards to prevent the location of HUD—assisted development in noise—
exposed areas. HUD pays particular attention to fostering land—utilization patterns for
housing and other municipal needs that will separate unconfrollable noise sources from
residential and other noise—sensitive areas. Finally, the EPA has identified noise levels
requisite to protect public health and welfare with an adequate margin of safety. The
levels specified by these three agencies differ significantly due to emphasis on different
aspects of noise impact. The quantitative and qualitative aspects of each of these
programs are discussed in ths section.
3.1 FHWA Noise Standards
Background
The Federal Aid Highway Act of 1970 contained a requirement that noise regu—
lot ions be developed for the planning and design of federal—aid highways. The Act
required that the regulations assign noise standards compatible with different land uses.
If further provided that the plans and specifications for a highway project could not be
approved unless they included measures adequate to comply with the standards. Interim
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Table 1
Desgn Ndse Leve i/Activity Relotionshps*
. Design Noise Levels—dBA 1
Activity
Category Leq 1 10 (h)
Description of Activity Category
A 2 57
(Exterior)
60
(Exterior)
Tracts of land which serenity and quiet are of extraordinary
significance and serve an important public need and where the
preservation of those qualities is essential if the area is to con-
tinue to serve its intended purpose. Such areas could include
amphitheaters, particular parks or portions of parks, open spaces,
or historic districts which are dedicated or recognized by appro-
priate local officials for activities requiring special qualities of
serenity and quiet.
2
67
(Exterior)
70
(Exterior)
Picnic areas, recreation areas, playgrounds, active sports areas,
and parks which ore not included in Category A and residences,
motels, hotels, public meeting rooms, schools, churches, libraries,
and hospitals.
72
(Exterior)
75
(Exterior)
Developed lands, properties or activities not included in
Categories A and B above.
——
——
For requirements on undeveloped lands, see Paragraph 11.a, and c.
52
(Interior)
55
(Interior)
Residences, motels, hotels, public meeting rooms, schools,
churches, libraries, hospitals, and auditoriums.
1 Either Leq or L 10 design noise levels may be used.
2 Parks in Categories A and B include all such lands (public or private) which are actually used as parks as well as
those public lands officially set aside or designated by a governmental agency as parks on the date of public
knowledge of the proposed highway project.
* Federal—Aid Highway Program Manual, Vol. 7, Chapter 7, Section 3.
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standards were adopted in April 1972, and an environmental statement on the standards
was circulated and reviewed. After consideration of the review comments, the flnal
standards were promulgated initially as Policy and Procedure Memorandum (PPM) 90—2
in February 1973, and revised as Federal Highway Program Manual (FHPM), Volume 7,
Chapter 7, Section 3, “Procedures for Abatement of Highway Traffic Noise and Con-
struction Noise” (FHPM 7-7-3), 1976. In addition, FI-IWA has prepared a manual
(The Audible Landscape: Manual for Highway Noise and Land Use) for local officials
to use to assist in compatible development in the vicinity of noisy highways. The manual
describes the administrative which local governments can use to control future
development. It also describes the physical measures which builders, architects, and
developers can use to comply with the local administrative controls.
Standards
The regulations require that a noise analysis be conducted for each highway
project. Noise—sensitive land uses and activities in the vicinity of highway projects
must be identified, and anticipated noise levels computed in 110 or t eq for the noise—
sensitive areas on the basis of the worst noise situation expected to occur from the
highway in question. The standards contain design noise levels of 110 or values
considered by FHWA to be the upper limits of acceptable noise levels for exterior land
uses and outdoor activities and for certain interior uses. These design levels are given
in Table 1.
Noise level predictions are to be compared with the appropriate design noise
levels to detemiirie the need for noise abatement measures for existing developed land.
Such mec ures are to be taken on all projects to meet the design noise levels to the
extent that reasonable opportunities exist to control noise. However, there are projects
for which abatement measures cannot feasibly achieve the desgn noise levels, and the
policy includes provisions for handling these exceptions.
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It is important to recognize several factors associated with these design levels.
• FHWA authorizes the use of federal funds for noise abatement wherever a
traffic noise impact can be identified provided only that the measures reduce
the noise impact and the overall benefits exceed the overall adverse social,
economic and environmental effects. (Para. 12, FHPM 7—7—3.)
• A noise impact can exist when:
(1) The predicted traffic noise levels approach or exceed the design noise
levels; or
(2) The predicted traffic noise levels substantially exceed the existing noise
levels. (Pam. 4, FHPM 7—7—3.)
• The design noise levels in the standards represent a balancing of that which
is desirable and that which may be achievable, and noise impacts can occur
even though the design noise levels are achieved.
• The values in Table 1 should be viewed as maximum acceptable values, with
the recognition that in many cases the achievement of lower noise levels
would result in even greater benefits to the community. Highway agencies
are urged by FHWA to strive for noise levels below those listed in Table 1
where they can be achieved at reasonable cost and without undue difficulty,
and where the benefits appear to clearly outweigh the costs and efforts
required. (Parc. 8, FHPM 7—7—3.)
• While the design noise levels apply only to lands which are developed on
the date of public knowledge of the highway, the standards indicate that
highway agencies may consider the desirabflity of applying them to unde—
velopeci ‘lands which are subject to development. In addition, highway
agencies are to furnish local officials with approximate generalized n&se
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levels For various distances from the highway improvement and other
information to assist and encourage local governments to develop and
implement programs (such as zoning or subdivision control) to protect
against future development which is incompatible with the expected noise
levels along the highway.
The above conditions do not apply to areas that have, or are expected to have,
limited human use, or where lower noise levels would result in little benefit. The exterior
design noise levels apply to outdoor areas that have regular human use and where a lowered
noise level would be of benefit to the public. The values do not apply to an entire tract
upon which the activity is based, but only to that portion of which such activity normally
occurs.
The interior design noise levels apply to:
1. Indoor activities For those parcels where no exterior noise—sensitive land
use or activity is identified.
2. Those situations where the exterior activities on a tract are either remote
from the highway or shielded in some manner so that the exterior activities
will not be significantly affected by the noise, but the interior activities will.
The interior design noise level may be considered as a basil for “soundprooflng”
public-use Institutional structures in special situations when, in the judgment of the high-
way agency and concurred In by the FHWA, such consideration is in the best interest of
the public. Interior noise level predictions may be computed by subtracting from the pre-
dicted exterior levels the noise reduction Factors for the building in question. If field
measurements of these noise reduction factors are obtained (or IF the factors are calculated
from detailed acoustical analyses), the measured (or calculated) values shall be used. In
the absence of field mea5Urements, the noise reduction factors may be obtained from the
following table:
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Noise Reduction Factors For Interior Noise Level Predicfons*
Building Type
Window Condition
Noise Re
Exterior
duction Due to
of the Structure
All
Open
10 dB
Light Frame
Ordinary Sash (Closed)
20
With Storm Windows
25
Masonry
Single Glazed
25
Masonry
Double Glazed
35
Federal—Aid Highway Program Manual, Vol. 7, Chapter 7, Section 3
Note: Recent work performed by Wyle Laboratories (“Insulation of Buildings Against
Highway Noise,” FHWA Manual FHWA—TS-77—202) validates these values for
their intended purpose.
Structures in climates where windows are open only a few days a year and
structures with air conditioning will normally be considered as a closed—window condition.
Situations where the open-window period does not coincide with a high noise level from
the highway may qualify as a closed—window condition.
The standards do not guarantee the elimination of annoyance or disturbance from
traffic noise even in those situations where the design noise levels are met. The standards
are those noise levels established for various activities or land uses which represent the
upper limit of acceptable traffic noise level conditions. These levels are used to
determine the degree of noise impact on human activities. Occasional peak noises,
such as th se which occur from the passage of a few trucks per hour, will not be controlled.
The reduction of these occasional noise peaks (and concurrent reduction of annoyance) will
come when the appropriate governmental agencies provide for reduction of vehicle source
noise levels, both through improved vehicle noise standards and enforcement of maximum
operating noise limits. However, the standards of Table 1, if applied, can ensure that
noise is given proper consideration in the development of highway projects.
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Eligible Noise Abatement Projects
FHWA permits federal funds to be used on federal—aid highway projects for the
abatement of traffic noise. The basis for the policy is to minimize adverse noise impacts.
It is recognized that these impacts are often difficult to quantify, but their reduction is
often justified in terms of the money spent.
Federal funds may be used for the construction of noise barriers and for the asso-
ciated acquisition of necessary land or land rights. Federal funds may also be used to
acquire lands (primarily undeveloped) as a preemptive buffer zone. Traffic operational
measures such as truck routes and restriction of hours of operation are often feasible noise
abatement measures. The increased costs of such measures are also eligible for federal
funding. In special situations., the “soundproofing” of public—use institutional buildings
may be incorporated in federal-aid highway projects to abate traffic noise. Current FHWA
policy regarding the use of Federal funds for private dwellings is that federal funds may be
approved under the National Experimental and Evaluation Program (NEEP) Project No. 21 —
Noise Insulation for Private Dwellings — based on the criteria established in FHPM 7—7_3,
Paragraph l2a; i .e •, ‘b traffic noise impact has been identified, the noise abatement
measures will reduce the noise impact, and the overall noise abatement benefits are
determined to outweigh the overall adverse social, economic, and environmental effects
of the noise abatement measures. The requirements of Paragraph 12e need not be met;
i.e., noise insulation may be implemented even if noise impact is not especially severe
and other abatement measures are feasible .“
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3.2 HUD Building and Development Site Noise Standards
Background
In August of 1971, HUD published an innovative policy on noise abatement and
control which indicated the Department’s intent to deal in a new manner with the noise
pollution problem. As set forth in HUD Circular 1390.2, this policy is directed toward
• Encouraging land utilization patterns for housing and other municipal needs
that will separate uncontrollable noi sources from residential and other
noise—sensitive areas; and
• Restricting HUD support for the construction of noise—sensitive development,
particularly housing on new sites which are adversely exposed to noise.
HUD’s policy is not to stop the building of needed housing, but rather to
encourage construction in areas which constitute good residential environments. The
Focus of this policy lies in HUD 1 s power to stop or alter plans for HUD—assisted housing
construction wherever noise levels are high.
Standards
In discouraging the construction of new dwelling units on sites having excessive
noise exposure, HUD has implemented the exterior noise standards which were established
in the 1971 Circular. The standards set Forth four noise level categories which are applied
to the site of the proposed construction. The four categories are: Acceptable, Discretionary—
Normally Acceptable, Discretionary—Normally Unacceptable, and Unacceptable. As set
forth in the 1971 Circular, the Acceptable category represents an ideal goal. In actual
practice, the Discretionary—Normally Acceptable category is used for acceptability
criteria and is combined with the Acceptable category.
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Approval of sites in the Unacceptable noise zone is strongly discouraged; only
the Secretary of HUD can approve such sites after an Environmental Impact Statement
has been Filed. At the other extreme, there are no special requirements associated with
the Acceptable noise zone, since sites in that zone are not considered to have a noise
problem. In the Discretionary—Normally Unacceptable zone, approval requires noise
attenuation measures, the Regional Administrator’s concurrence, and a detailed environ-
mental statement as defined by Section 102(2)C of P191-190 and implementing guidelines
of the Council on Environmental Quality and HUD.
HUD realizes that in densely developed urban areas in particular, land available
for development is scarce or is subject to a variety of constraints in development, so
that the total housing needs of an area often cannot be accommodated without some
development in areas impacted by noise. In such circumstances, approvals in
Discretionary—Normally Unacceptable areas are authorized, but only to the extent
that the area’s housing needs cannot be reasonably accommodated in areas not
exposed to noise.
The rules of discretion, as applied to HUD’s noise policy, are designed to
accommodate the Department’s mandate to provide both a “decent home” and a
“suitable environment” to American families. If it is truly a choice between housing
with some noise, or no housing at all, then it is HUD’s policy to assist the housing and
to minimize the noise impact through noise attenuation measures. IjUD only requires
that the true extent of the trade—off between housing and noise be established.
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Noise Reduction Features
In the past four years, since implementation of the noise policy, many instances
have occurred in which noise attenuation measures have resulted in basic project design
modifications and the incorporation of double—glazed windows, solid wood doors, air
conditioning, and other acoustical features necessary to reduce and prevent the encroach-
ment of noise upon the potential homeowner or apartment dweller. The additional cost
of the noise reduction features is absorbed by the developer and ultimately by the buyer.
Such costs can often be avoided or reduced by planning for noise and taking it into con-
sideration in the earlier site selection and site planning stages of the project.
Clearly, this policy has made it advisable for local and area—wide agencies
responsible for housing and land-use planning to conduct studies to establish a strategy
for the location of housing in a land-use plan which accounts for noise as well as other
environmental concerns. In the absenáe of a planning strategy which addresses noise,
developers must document the need for the proposed noise—sensitive development in order
to obtain HUD assistance. This can be a time—consuming process resulting in the rejection
of some projects in areas exposed to noise, if alternative and less exposed sites exist or
the lack of such sites has not been adequately established.
3.3 EPA Identified Levels
In March oF 1974, EPA published a document entitled Information on Levels of
Environmental Noise Requisite to Protect the Public Health and Welfare with an Adequate
Margin of Safety . The levels identified in this document are based solely upon public
health and welfare considerations and are presented in Table 2. It is important to note
that these levels were established without consideration of cost or feasibility, and hence
they do not represent an agency standard. Unlike an agency standard, levels which are
in excess of those idenjified may be appropriate in individual cases and no special pro-
cedures or exemptions are necessarily recommended. On the other hand, an adverse
impact on the public health and welfare does exist for levels in exàess of those identified
and it is this impact which must be traded—off against the cost, feasibility of achievement,
and the attainment of other objecflves in making final decisions. These levels are therefore
considered by the EPA as goals to be strived for , with the recognition that the time for
actual achievement in individual cases will depend on a variety of other considerations.
19
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Table 2
Summary of Noise Levels Identified As Requisite To Protect
Public Health and Welfare With An Adequate Margin of Safety*
Effect
Level
Area
Hearing Loss
L < 70 dB
eq(24) —
All areas
Outdoor Activity
Interference and
Annoyance
L < 55 dB
dn —
Outdoors in residential areas and
farms and other outdoor areas
where people spend widely varying
amounts of time and other places
in which quiet is a basis for use.
Le (24) < 55 dB
q
Outdoor areas where people spend
limited amounts of time, such as
school yards, playgrounds, etc.
Indoor Activity
Interference and
Annoyance
I < 45 dB
dn —
Indoor residential areas
L < 45 dB
eq(24) —
Other indoor areas with human
.
activities such as schools, etc.
* “Information on Levels of Environmental Noise Requisite to Protect Public Health
and Welfare With an Adequate Margin of Safety”, Report No. 550/9-74-004,
U.S. Environmental Protection Agency, Office of Noise Abatement and Control,
March 1974.
20
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3.4 Land—Use Compatibility Guide
The use of land for compatibility with various noise environments is illustrated
in Figure 1 • The choice of the use is governed by the 1 dn values describing the noise
exposure. There is no universal method of rigidly interpreting requirements — this must
be done on an individual basis with consideration for local constraints.
For most land uses, the conçrntibility interpretation for the lower Ldfl values
Indcates that there are no special noise insulation requirements for new construction,
and that there should be no adverse effects from transportation noise. Corresponding
to higher levels of noise exposure, the interpretations generally define a range of noise
exposure in which new construction or development should not be undertaken but could
be allowed where restrictions are not possible due to local land development constraints.
In such cases, an analysis of noise reduction requrements should be made and needed
noise reduction features included in the site development and building design.
A major factor to be considered in detemilning noise requirements for a given
land use is the local building construction. The quality and type of wall, window and
roof constructions are among the most effective ways of reducing the number of noise
leakage paths. This is one of the key areas of control by local authorities through local
building and safety codes.
21
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For Residential, Hospital and Educational
Activity
Environmental Noise Level’
Associated with an Action
(exterior environment)
/5
70
65
60
55 —
Qualitative Considerations Applicable to
Individual Actions
Levels are generally acceptable: noise impacts
are not usually associated with these levels
* Interior noise levels will depend on the building structure.
Figure 1. Representation of Land—Use Compatibility With Noise.
Levels have unacceptable public health and
welfare impacts
C
0
-J
a,
-J
-v
C
0
U)
a,
C o
a,
>
-c
z
>-
Co
0
Significant adverse noise impacts exist:
allowable only in unusual cases where lower
levels are clearly demonstrated not to be
possible
Adverse noise impacts exist: lowest noise
level possible should be strived for
22
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4.0 APPROACHES TO NOISE CONTROL
The federal policy requires that every reasonable effort be made to achieve
substantial noise reductions when noise impacts are identified. However, any signif-
icant reduction in the existing or predicted noise levels will be a benefit, so that the
inability to comply with the standards does not imply that noise abatement measures
should not be incorporated. Thus, measures to achieve partial reductions in noise level
shall be included in the project development where they are consistent with overall
social, economic, and environmental considerations.
Furthermore, since the standards represent a balancing of that which is desirable
and that which may be achievable, noise impacts can occur even though the standards
are achieved. Accordingly, the standards should be viewed as maximum acceptable
values recognizing that lower levels will result in an increase in community benefits.
It is recommended that measures be introduced to reduce noise levels to values below
those of the standards in cases where the benefits appear to outweigh the costs involved.
For a more detailed definition of federal policy, the reader is referred to Sec-
tion 3 of this manual, or to the Federal Highway Program Manual, Vol. 7, Chapter 7,
Section 3.
In order to control highway noise in the most effective manner, it is generally
agreed that a three—part approach is needed. The elements of this approach are as follows:
1. Reduction of sound at the source (the motor vehicle).
2. Noise control measures in the planning and design of highway projects.
3. Control of the use of land in the vicinity of highways.
Each of these approaches will be discussed in detail in the following sections.
4.1 Reduction at the Source
The reducflon of noise at the source — that is, on the vehicle itself — is poten-
tially the most fruitful way to reduce the problems of motor vehicle noise. Whereas the
application of other techniques, such as land planning and increased building insulation,
may provide local abatement of noise, a quieter vehicle will produce lower noise levels
23
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wherever if travels. Also, quieter vehicles can provide a reduction of noise along
existing highways where no other corrective measures are possible.
There are basically two methods available for reducing vehicle noise at the
source, namely:
• Operational limits , where existing vehicles are required not to exceed a
specified noise level. Vehicles producing levels below the limit would
not be affected; those exceeding the limit must be brought info compliance
by repair, retrofitflng, or eflminating. A Certain degree of non—compliance
is inevitable and should be included in a&y assessment of the effectiveness.
• New vehicle limits , where new vehicles are required to meet specified
noise standards. The standard for new vehicles can be substantially lower
than an operational limit, because new technology is more readily incor-
porated info new vehicles than into existing ones.
Any realistic strategy must incorporate both types of limits. The operational
limit alone does not provide for maximum use of new technology; new vehicle regulations
alone do not provide for control of vehicles once they are in service. Strategies may
also include lowering both types of limits with time, as noise control technology improves.
The Environmental Protection Agency (EPA) has promulgated noise emission
standards for motor carriers currently engaged in interstate commerce, and FHWA/
BMCS (Bureau of Motor Carrier Safety) has enforcement responsibility for these standards.
EPA has also promulgated noise standards for newly manufactured medium and hecr ry duty
trucks. In states where these laws (or similar prior state laws) have been actively enforced,
reduced vehicle noise levels have been observed.
There is one important difference between the two methods for regulating vehicle
noise levels. The operational noise limit is a limit to be met by all vehicles, and if
properly enforced, will result in an immediate reduction in highway noise. The new
vehicle noise standards only apply to the vehicles introduced into the fleet, and even
though they might be much quieter than existing vehicles, the full effect is only obtained
24
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after many years of attrition of older vehicles. As a result, it might be assumed
that the operational noise limit represents the Optimum method of vehicle noise control.
Unfortunately, it is quite difficult to significantly reduce the noise levels of existing
vehicles— some of which may be 10 years old— without considerable expense.
Accordingly, the benefits to be obtained from vehicle noise reduction will not be
fully realized for many years.
An alternative method of reducing vehicle noise at the source is to modify the
operation of the vehicle. Although this is actually a highway design or operating
approach, its effect is the same as a source reduction, arid is therefore treated here.
There are two ways in which this can be achieved:
• Reducing Truck Traffic
Restricting the number of trucks operating on the highway can be a very
effective solution to high noise levels. Table 3 shows the effect for
speeds of 35 and 55 milesper hour (mph). For example, a change from
15 to 5 percent truck traffic traveling at 55 mph will result in a decrease
of about 4 dB in overall highway noise. Completely eliminating trucks
on specific roads through the use of alternate truck routes in compatible
areas would result in a decrease of 8.5 dB. Even greater reductions can
be obtained in speed zones of 35 mph.
• Reducing Truck Speed
Highway noise levels can also be reduced by limiting the speed of trucks.
This s useful only on high—speed roads where flre nose dominates and is
reduced with decreasing speed 0 The reduction in overall highway noise
is given in Table 4.
25
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Tables 3 and 4 can be used to determine the change in highway noise levels
resulting from changes in truck flow and speed. For example, if the existing truck
percentage is 20%, traveling at 55 mph, the effect of reducing the percentage to 10%
and the speed to 35 mph can be obtained as follows:
• Find the reduction in noise level due to a change in truck percentage
from 20% to 10% at 55 mph From Table 3 ( 2.5 dB).
• Find the reduction in noise level due to a reduction in truck speed
From 55 mph to 45 mph at the new percentage of 10% from Table 4 ( I dB).
• Find the total change in highway noise level by direct addition ( 3.5 dB).
Table 3
lithe Charge in Truck
Percentoge Is from:
Then the Reduction in l-lTghway Noise Level
(L orL )indBis;*
eq dn
35 mph —
55 mph
20% to15%
15% to 10%
10% to 5%
5% to 0%
1
1.5
2.5
6.5
1
1.5
2.5
4.5
* The reductions in those columns ore additive, so thot, for example, the
reducton in hghway noise level resulting Irons a change in truck percehtage
from 20%to5%ot 35 mph is I + 1.5 + 2.5 = 5dB
Table 4
The Effect on Highway Noise Levels of Reducing Truck Speed
Change In Truck ,ecd
nph)
From — To
/s.pproxmalo Rcciucton in Highway
Noise level or 1 dn
Truck Mix
5% 10% 20%
65 — 55
65 — 45
65 — 35
55 — 45
55 —. 35
45 — 35
0.5 1.0 1.5
1.0 1.5 2.0
2.0 3.0 3.0
1.0 1.0 1.0
hO 2.0 2.0
1.0 1.0 1.0
The Effect on Highway Noise Levels of Reducing Truck Traffic
26
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4.2 Noise Control in Highway Planning and Design
The second part of the three—part approach is the abatement of traffic noise
in the planning and design of highway projects. A consideration of this approach is
required by the FHWA noise policy before federal funds can be allocated to a highway
project. The methods of abatement that are available include the selection of highway
location, the depression of the roadway, the introduction of barriers, and the sound-
proofing of buildings. The effect of each of the road design methods can be determined
by the procedures described in Appendices A and B.
In the planning and design phase, the following factors should be considered:
• An effective measure for minimizing noise impact involves adjustment of
the alignment to avoid sensitive receptors, such as schools, hospitals,
and residential areas.
• Since the topography of an area may be used in some instances to reduce
noise, horizontal adjustments may be appropriate in order to take advantage
of shielding by existing terrain.
• Adjustments to the profile and cross—section may effectively reduce noise.
While elevated facilities generally have a limited ability to contain noise,
the knee of the slope may act as a barrier which satisfactorily reduces noise
levels at adjacent receptors. However, a more effective vertical adjust-
ment of the alignment involves depression of the roadway. Depressed
alignments, particularly those between deep retaining walls or with
covers, are effective means of containing noise.
• Other design considerations include the modification of roadway gradients.
Steeper gradients will normally increase traffc noise levels.
27
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4.2.1 Barriers
An alternative to either source noise reduction or receiver protection consists
of the incorporation of acoustic barriers between the noise and the receiver. Barriers
are generally considered to be feasible only along major highways with long, uninter-
rupted stretches of road. Barriers are not usually considered for local streets due to the
many interruptions that would occur for crossing streets.
While much literature is available on the theoretical effectiveness of noise
barriers, the basic consideration remains the effective height of the barrier relative
to the flne of sight between the source and the receiver. Borri s have been designed
to provide attenuaflon over the range from 5 to 15 ciBA, with the median value being
10 dBA. The 15 dBA value represents the maximum practical design limit.* The cost
of barriers varies greatly not only with the type of material used, but also with the
location and the existing ground surface.
The attenuation provided by a barrier is dependent on the geometry of the
source—barrier—receiver system, and can be incorporated into the noise assessment by
means of the nomogram procedure given in Appendix B.
The material used for consfructing the barrier must be selected so that the trans-
mission of sound through the barrier is much less than that diffracted over the top. In
general, this can be achieved by ensuring that the mass of the barrier material is at least:
• 1 .3 lbs/ft 2 for an attenuation of 5 dB.
• 2.3 lbs/ft 2 for an attenuation of 10 dB.
• 4.0 lbs/ft 2 for an attenuation of 15 dB.
* Snow, C.H., “Highway Noise Barrier Selection, Design and Construction Experiences,
A State—of—the-Art Report — 1975”, U . S. Department of Transportation, F HWA
Implementation Package 76-8.
28
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4.2.2 Noise Reduction at the Receiver — Dwelling Modifications
For ground transportation noise sources, it may be possible to achieve desired interior
noise levels through treatment only of walls facing the source. The soundproof ing treat-
ments and the relative effort involved in these modifications are summarized below under
the categories of minor, moderate, and major dwelling modifications.
Minor Dwelling Modifications
Through attenuation to details such as minimization of “sound leaks” around doors,
windows,and vents and replacement of “acoustically weak” components, outside to inside
noise reduction of A—weighted noise levels .n the order of 25 to 30 dB is obtainable.
These improvements consist primarily of adequate weatherstripping around doors, assur-
ance of snug—fitting doors and windows, elimination of louvered windows and treatment
of exterior vents (chimneys and kitchen or bathroom fans, in particular). In addition,
exterior hollow-core doors need to be replaced with the solid-core variety. This treat-
ment essentially ensures that the noise reduction provided by the dwelling structure is up
to the performance capabilities of the building elements and is not affected by leaks, etc.
Moderate Dwelling Modifications
Moderate modifications would include all of those listed under “minor” plus major
attention to the weakest housing components — namely, windows. The most effective window
treatments consist of double glazing or sealed windows. In both cases, this usually neces-
sitates the installation of a mechanical venHlating system or air conditioner in the dwelling,
if it is not already done. Additional attention is given to the attic by acoustical treatment
of attic vents, inc eased sound absorption material (hence, better heat insulation) in the attic
space, and when required, finishing the crawl space areas wtth gypsumboard. Such treatments
will produce overall sound insulation on the order of 30 to 35 dB for A—weighted noise levels.
Major Dwelling Modifications
Major modifications consist of all items under “minor” and “moderate”, plus some
structural improvements of weak walls and roofs. These changes would include elimination
or suitable modification of exposed beam roof/ceiling designs and a general “beefing up”
of exterior walls. Sufficient exterior wall improvement may normally be attained by
29
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installation of an extra layer of gypsum board on the interior surfaces over sheets of
sound—deadening board or by securing it to resilient channels. Where possible, double—
entry doors or vestibule entrances could be incorporated. In lieu of these, “acousflc”
doors are required. Improvements in sound insulation available from these changes may
yield noise reductions on the order of 40 dB for A-weighted noise levels.
The cost of modifying dwellings depends on the construction type, the geograph-
ical area and the degree of noise reduction required. For minor and moderate modifica-
tions, the noise reduction can be increased by 4 to 9 dB at a cost (in 1976 dollars) of
between $3 to $7 per square foot oF dwelling area. Majo modifications, that can increase
the noise reduction by up to 15 dB cost about $14 per square foot. These cost figures are
intended as a guideline only and must be estimated on an individual basis.
In view of the expense involved, it is recommended that this approach be consi—
dered only as a last resort — particularly since the exterior noise environment remains
unaffected.
To achieve compatible land use through improved sound insulation in building
structures, it is necessary to amend the building code to achieve two objectives:
• Incorporate adequate exterior to interior noise reduction in new construc-
tion to abate external noise, and
• Establish minimum requirements for internal noise reduction in multi—family
dwellings, hotels, and motels to achieve desired acoustical privacy.
Both of these changes provide a legal basis for noise abatement which is of direct
benefit to the people and is not costly to implement.
An important aspect in the application of noise control techniques to houses is
the fact that the sound levels at various points around the outside of a house will differ
by virtue of the acoustic shielding provided by the house structure itself against the noise
source. This is similar to the formation of a shadow in the case of light, It is passible to
make use of this effect in soundproofing since the shielding is equivalent to an increase
in attenuation of the shielded wall or window. Thus, the shielded elements of a house
are not required to provide the same degree of attenuation as are the unshielded walls.
30
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For highway noise sources, this self—shielding will reduce by about 10 dB the noise
levels on wall surfaces facing directly away from the traffic. The shielding for the
side walls is usually in the neighborhood of 3 dB.
4.3 Land Use
The third part of a balanced attack on highway noise is control over the use of
land in the immediate vicinity of the highway. This does not necessarily mean that this
land remain vacant. Many commercial and industrial activities can exist within a mod-
erately noisy environment, and many other types of activities can be accommodated
through proper site location, building design, and acoustical treatment (soundproofing).
Often, complaints about highway traffic noise come from residents occupying
homes built adjacent to a highway after the highway was already built. Many of these
highways were originally constructed through undeveloped lands. Even though highway
agencies may be knowledgeable about existing zoning and planning, they are not able to
control when and where future development will occur, what such development will be,
and the degree of ‘soundprooflng” that will be built into future buildings. Moreover,
there are existing highways which are bordered by vacant land which will someday be
developed. Sensible land use control implemented at an early stage can help prevent
future traffic noise conflicts in these areas. Such controls need not prohibit development;
rather, they should utilize reasonable setback distances, appropriate zoning, or other
previously discussed abatement measures to avoid future noise disturbances.
Federal funds may be used in the acquisition of real property or interests therein
(predominantly unimproved property) to serve as a buffer zone to preempt development which
would be adversely impacted by traffic noise and for other noise abatement purposes. Acqui-
sition of a few improved parcels may be included in such buffer zone acquisitions to provide a
uniform treatment. Further, it is preferred that buffer zone acquisition be performed in con-
junction with local zoning, land use controls, or other local government controls imposed or
exercised in accordance with a comprehensive plan. Mditional details regarding FHWA land
acquisition policy may be found in the FHWA Federal—Aid Highway Program Manual 7—7—3,
Paragraph 12b (5).
31
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4.4 Eva luaf ion of Proposed Measures
The steps involved in the evaluation of noise abatement methods are as follows:
1 • Determine the amount of noise reduction required to satisfy the noise standards.
2. Assess the noise reduction that can be achieved by the methods proposed in
the EIS. For this purpose, calculation methods are contained in Appendices A
and B and earlier parts of Section 4.0. Appendices A and B contain the basic
method for calculating highway noise levels; Section 4.0 contains infonnation
suitable for determining the effectiveness of abatement methods. Discrep-
ancies between the predicted amounts of reduction should be resolved with
the persons responsible For preparing the EIS.
3. Evaluate the methods proposed against the reduction required.
4. Identify alternative or additional measures that are suitable for implementing
the federal policy of n&se abatement.
32
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APPENDIX A
Highway Noise Nomogram Procedure*
The procedure for Computing highway noise levels involves the use of nomograms,
which, when entered and read properly, allow easy use of the relationships between
highway noise variables to determine values of Leq• The step-by-step procedure
involves a determination of Leq for a straight roadway segment at a single observer
position.
• The procedure is directly applicable to straight road elements. A curved
road may be considered to be straight iF it deviates From straight by less
than 10 percent of the observer distance, D, for a distance ±5D (or the
section length if less) from the nearest point. This tolerance is illustrated
in Figure A—i. Trealment of roads with greater curvature is discussed later.
4 5D 5D
Figure A—i. Permissible Curvature for Approximately Straight Roads.
• IF more than one roadway is present, then the noise level from each roadway
must be computed separately by using the nomogram procedure. The
perpendicular distance from the observer to each roadway must always
be taken.
* See Appendx C for documentation and validation of this procedure.
Al
-------
• Finite road elements are defined by the angles e. and as shown in
Figure A-2. If the observer does not lie between the end points, the
observer distance D is measured perpendicular to an extension of the
section, as shown in Figure A—2b.
b. Observer Not Between End Points. The smaller of the angles (e 2 n
case) s given a minus sign.
Figure A—2. Geometry and Angle Definitions for Finite Road Elements.
a. Observer Between End Points.
End Point
D
Observer
A2
-------
• A curved road may be divided into two or more approximately straight
elements, each with tolerances as shown in Figure A—i. An example is
shown in Figure A—3. For each section, the observer distance, D, is
measured perpendicular to the section or ifs extension.
Extension of
• After all of the roadways and/or sections have been accounted for and the
resulting L ‘s have been tabulated, the total I is obtained by combining
eq eq
the individual values,usng Noniogram A5, as shown in the procedure.
• If Ldn is being calculated for a highway section orsections, then separate L ’s
must be determined for the daytime hours (Ld, 0700—2200) and the nighttime
hours (I ,2200—0700). L can then be obtained from Tables Al and A2.
n dn
• If 1 eq is desired at more than one single observation point, then the entire
step—by—step procedure must be repeated for each additional observer position.
(The user will note, however, that a good number of the steps are independent
of observer position, so the procedure s not as complicated as it may initially
seem.)
2
Observer
Figure A—3. Curved Roadway Approxmated by Two Straight Sections
A3
-------
Table Al
Method for Calculating L from L. and L
dn d n
If the
L
d
Value of
— I k:
n
Then Add this Num
to Determine
ber to Ld
L ‘
dn
—4dB
10dB
-2
a
0
6.5
2
5
4
3.5
6
2
8
1
10
0
12
-0.5
14
-1
16
-1.5
Table A2
Method of Calculating L from L When the
dn eq
Day/N ight Traffic Percentage is Known
If the Percentage of 24-Hour Traffic Then Add this Number to L 4)
Passing During Daytime Hours Is: to Determine 1 dn
100% 0 ciB
95 1.5
90 3
8 .5 3.5
80 4.5
70 5.5
60 6.5
50 7.5
8
A4
-------
Table A3 lists required input data, and specifies units. Table A4 defines
symbols used in the calculation procedure, and indicates the step in which they are
defined. Figure A4 shows the dimensions defined in Table A3.
The procedure in this appendix is to be used only if a clear line—of—sight
exists between the observer and the road surfcce. If this line-of—sight data does not
exist, then the barrier procedure given in Appendix B must be followed.
The nomogram calculation procedure consists of the following steps, with a
running numerical example following each of the steps. Worksheet A, shown
on page A7, may be used to record the input data and The values obtained along
each step of the nomogram procedure.
If a calculator with common logarithm, antilogarithm, and square root functions
is available, some users may find it more convenient to calculate quantifies. Where a
simple equation exists, it is shown on the nomogram.
Figure A4. Roadway Dimensions
Far
Lanes
Observer
D
A5
-------
Table AS
Input Quantities Used in the Nomogram Procedure for Computing Highway Noise Levels
Variable
Meaning
Units
S
Average speed (if not available, use posted limit)
mph
Q
Total vehicle flow
vehicles/hr
I
Truck flow 1
trucks/hr
M
Distance between centerlines of inner (left) lanes
feet
W
Distance between centerlines of outer (right) lanes
feet
D
Distance from point of measurement to centerline
of nearest lane
feet
G
Roadway grade
percent
e ,
e
Angles defining road section ends
degrees
1 IF Ld is being calculated, separate values are needed for the hours of 7AM to 10 PM,
and 10PM to 7AM.
Table A4
Symbols Used in the Highway Noise Nomogram Method
Variable
Meaning
Units
Step Number
In Which
Variable_Is_Defined
L
t
GF
E
i
w
Base Noise Level
Percentage of Trucks
Grade Factor.
Effective Truck Percentage
Truck Noise Increment
Distance Adjustment
Road Width Correction
dB
percent
-——
percent
dB
dB
dB
I
2
2
2
3
4
5
A6
-------
WORKSHEET A
NOMOGRAM PROCEDURE FOR COMPUTING HIGHWAY NOISE LEVELS
(See Text for Step-by—Step Instructions)
REQUIRED DATA
STEP I
STEP 2
STEP 3
STEP 4
STEP 5
STEP 6
Average Speed,
Total Vehicles Per Hour,
Trucks Per Hour,
Distance between Centerlines of Inner Lanes,
Distance Between Centerlines of Outer Lanes,
Distance from Obs.rver to Centerline of Nearest Lane,
Roadwoy Grade,
Angles Defining Road Section Ends,
I — ___________ dBA
1 .q T”
(from STEP 3) (from STEP 4) (from STEP 5)
STEP 7 If — 82 * 90’, us from STEP band terminat. i,roc.dur..
•1
dB
82 AA 2
• (1 —
sq 1 eq 3 ’ A 1 dB
(from STEP 6)
L — (I —
sq 2 eq =
(From STEP 6)
dB
dB
S — __________ mph
o = ______ perhour
T • ________ p.rhour
M __________ ft
W _____ ft
_____ ft
G- ____
1 degrees
‘2 degrees
_____________d O
STEP 8
(L ______)+(L ______) ________dB
eq 1 eq 2
(from STEP 7) (from STEP 7)
(NOTE: L must be larger than L ; if not, reverie them.)
eq 1 eq 2
Combined L 1 q dO
t — x1O0
E — tx(GF _____) — _______
— dB
________dO
M
w*
w
15•=
dO
I
A7
-------
STEP 1 Enter Nomogram Al with Q and S to obtain the base noise level, L.
(Example: For Q 6000/hour and S = 55 mph, L = 75.5 dBA)
STEP 2 Calculate the truck percentage, t, by dividing Q into I and then
multiplying by 100. Enter Table A5 with the roadway grade, G, to
obtain the grade factor OF. Multiply the truck percentage, 1, by the
grade factor, GF, to determine the effective truck percentage, E.
(Example: For I = 300/hour, t = 5%. For 0 = 2%, OF = 1.4 or that E 7.0)
Table A5
Roadway Grade and Grade Factors
Roadway Grade, 0
Grade Factor, GF
<2%
2to6%
>6%
1
1.4
2
STEP 3 Enter Nomogram A2 with S and E to obtain the truck noise increment
(Example: i = +6 dB)
STEP 4 Enter Nomogram A3 with D to obtain the distance correction In
typical cases where propagation is over the ground, the scale marked
“Over Ground” is to be used. This scale includes normal ground absorption.
Where the geometry is such that ground absorption does not occur (as described
on the rromogram), the scale marked “Free Space” is used. The free space
scale is also used in the barrier calculation described in Appendix B.
(Example: For D = 200 Ft, D = -8.3 dB)
A8
-------
STEP 5 Enter Nomogram A4 with M/W and W/D to obtain the road width
correction Factor,
(Example: For M = 32 ft and W = 80 ft, tv’y’W = 0.4 and W/D = 0.4 From
Nomogram A4, = -1 dB)
STEP 6 Determine the equivalent noise level, by adding the three corrections
to L:
L =L+ + +
eq T D W
Note : The correction Factors D and are always zero or negative.
(Example: ‘eq = 75.5 + 6 - 8 - I = 72.5 dBA)
Note : As a result of vehicle noise regulations, the individual noise levels
of vehicles will decrease with time. The effect of this reduction can be taken
into account by correction factors applied to LeqI as described in Appendix D.
STEP 7 If and 2 are not each 90° (an assumed infinite road), a correction
must be applied. Table A6 gives this correction for a symmetric road with
half angle e = = 62 1 For 6 e 2 , divide the road into two ports at 6 = 0.
Subtract 3 dB from L to get the noise for each half, add from Table A6
eq A
to the resulting levels For each half, then combine the sections as per STEP 8.
(Example: 0. = = 90°, A = A = 0. Use 1 eq from STEP 6 and terminate
procedure) 1 2
(Example: 6 60°, t =-1.2,
6 2 0 ’ A =-2.8,
2
L 72.5 — 3dB = 69.5
eq
L = 69.5 + (-1.2) = 68.3
eq 1
L = 69.5 + -2.8) = 66.7)
eq 2
A9
-------
Half Angle
Table A6
9 and Correction Factor
If the Half Angle 9 is:
Then the Value of in dB is:
10°
-8.7
20°
-5.7
30°
-4.0
400
-2.8
50°
-1.9
0
-1.2
70°
07
80°
-0.3
90°
0
STEP 8 If the highway is divided into sections, or if there is more than one highway,
then the noise levels associated with each are combined. Enter Nomogram 5
with 1 eq 1 and Leq 1 — Leq 2 If there are more than two sections and/or highways,
Nomogram A5 is repeated ly applied to combine each 1 eq to a running total.
This completes the nornogram procedure.
(Example: I = 73, L = 68, 1 = 70. Combine I
eq 1 eq 2 eq 3
combine this with 1 eq 3 to obtain 75.6)
If the geometry of a finite rood element is such that one ciigle is negative (as in
Figure A—2b), Nomogram A5 must be used “backwards” to subtract the negative portion.
ConsIdering 01 > 02, and denoting the respective 1 eq’ by cq 1 and L q 2 I there are
two Cases:
1. L q 1 q 2 > 3 dB. Enter Nomogram AS with L 1 on the Leq 1 scale,
and adjust the straightedge such that L q 2 + equals the value on the
scale. This value on the 1 eq 2 scale is the answer.
eq 1
and L to obtain 74.2;
AlO
-------
2. — < 3 dB. Enter Nornogram A5 with on the 1 eq 1 1 scale,
and It on the I scale, Subtract the resultant A from 1’ to obtain
eq 2 eq 1 eq 2
the answer.
Alternately, the equation may be used replacing the plus sign with a minus sign.
In some cases, the highway or the local terrain may be too complex to be treated
by the simple nomogrom method which can only handle fafrly orthodox configurations.
It will therefore be necessary to resort to a computerized method of calculation that can
account for these situations. Available methods are described in Appendix C.
All
-------
Enter with Qand S.
Exit with L.
50,000
NOTE: If Qis less than 100,
90
multplyQby 10, then enter.
Subtract 10 from resultant L.
20,000
85
10,000 75
,,000 50
5,00
7,000
6,000
63
5,000
4,000
Equation:
L0.4+ 0Iog 10 Q
2,000 +22109105.
45
1,000
900 63
800
700 40
600
500
60
55
Q L 25
NomogramAl. Calculation of Base Noise Level, L.
• 12
-------
—20
18 30
25
Equation: 25
a( ] 20
15
where
a =9.82
S<35mph
b=3.2 —
10
a33.7
b=1.2 S35mph 6
$
2
Enter with S and E.
Exit with
2
4
0.B
0.6
43
30 0.4
55 0.5
6
0.2
65
70 —
75 0.)
S Nomogram A2. CaIci Iation of Increment due to E
Truck Traffic.
A13
-------
-4- 0 0 50
P
—5
—5
-10
Enter with D, using Pivot Point P -10
Exit with A
D -15
—20 —15
300
Use “Free Space” AD scale if the -25
angle between the line of sight from -20
the road surface to the observer and the Free space
terrain is 10 degrees or greater. This scale 600
is also used for barrier calculations. (See Appendix B). -25
-600
- cvo
L .1o( 0
D
Equation: Over Ground
fD\ / D-50 ’
AD -a log 10 - ,) - I\ 500’
2000
where i
a 13.3, over ground
10.0, free space
I. 3000
D
Nomogram A3. Calculation of Correction AD for Distance.
-------
.M W
Enter with— and—.
• W D
•EXitWith W.
1.0
4)
0.8
0.7
0.6
0. 5
0.4
0.2
0
Ncainogram A4. Calculation of Correction Factor for Road Geometry.
Equation:
No simple equation exists
‘I
1 .
w
D
w
0.4
0.3
0
A15
-------
0
90 93
90
2
3
.4
5
6
8
80 80 10
15
20
( 1 -ec — Leq
70 Equation:
1 f Leq/10 Leq/1O
= 10Iog1A 1O ‘ + 10
IV
60
Note: cq 1 is to be the higher of the two noise
60 Jevels being combined,
5
L
eq 0 0 ,
50
NomogramA5. Nomogram for Combining the Noise Levels from Two Highways
A16
-------
APPENDIX B
Barrier Nomogram Procedure
If there is a barrier alongside the highway, or if the highway is depressed,
the result will generally be a reduction in noise level. The effect of the barrier will
be different for cars and trucks because of the different noise characteristics and noise
source locations and the two types of vehicles. The barrier effect is incorporated into
the highway noise nomogram procedure presented in Appendix A by the mechanism of
modifying the actual number of cars and trucks in order to achieve the applicable
noise reduction. If there is more than one traffic lane, the following procedure must
be applied to adjust the car and truck volumes in each lane. If many lanes are involved,
the calculation can be lengthy. Simplifications in the procedure are not feasible, how-
ever, because shielding is very dependent on the geometry. Unacceptably large errors
could result if lanes were grouped.
Data required for the barrier calculation, in addition to that specified in
Appendix A, are listed in Table Bi. Additional quantities used in the procedure are
listed in Table B2. Figure B—i illustrates a highway—barrier situation and the symbols
used in the nomogram procedure.
Bi
-------
Table Bi
Input Data Items Required For
Barrier Nomogram Procedure
Table B2
Symbols Used in Barrier Nomogram Procedure
Variable
Meaning
Step Number
In Which
Variable Is Defined
a,b,c
Intermediate quantities used in
finding path length difference
1,2,3, respectively
6
Path length difference
4
H .
crit
Critical barrier height
4
Barrier
Factor
‘Adjustment” to traffic flow
volumes due to barrier
5
Q’
Adjusted vehicle flow for cars
6
1’
Adjusted vehicle Flow for trucks
6
Note: The quantities a,b,c,6, and Barrier Factor are elsewhere referred to with
subscripts C and I denoting cars and trucks, respectively.
Meaning
Horizontal distance from observer to barrier.
Horizontal distance From barrier to center
of lane.
Total distance from observer to center of
lane.
Barrier height, relative to road surface.
Observer height, relative to road surface.
Barrier included half—angle.
B2
-------
a) Roadway and Barrier Cross-Section. Heights are Measured From
Road Elevaton.
b) Roadway Plan
Figure B-i • Dimensions for Barrier Procedure.
Barrier
A
Road
D 0
D
Roadway
Barrier
Observer
B3
-------
The following points should be noted with regard to these data:
• The barrier height, HB, and the observer height, H 0 , are always meas-
ured relative to the roadway . Thus, in the case of an elevated highway
section with no side barrier, the barrier height would be the same as the
roadway (typically) which yields a barrier height, 1 1 B = 0. The observer
height would then have (typically) some negative value.
• For a depressed highway, the barrier height would be equal to the height
of the ground level above the depression. The observer height would be
greater than the barrier height.
• 0 B’ the barrier—included half—angle, is one—half of the angle subtended
by lines of sight from the observer to the ends of the barrier. For an infinite
barrier, 0 B = 900 If the barrier does not cross the closest line of sight to
the road, shielding will be less than 3 dB, and is not of any useful benefit,
bulk of the barrer calculation involves finding the path length difference 6
8A+B —C
where A, B and C are defined in Figure B—2.
Source
Figure B—2. Illustration of Path Length Difference (6 = A + B — C).
The
as defined as:
B
A
Receiver
C
B4
-------
Because cars and trucks have different effective source heights, 8 must be computed
separately for each.
Path length difference may be computed either of two ways, depending on
whether a calculator is available.
1 • If a calculator with square root function is available, use the following
equation:
2 2 2 2 2 2
6 = [ (He — H 0 ) + D 0 ] + [ (HB — Hs) + DH] — [ (H 0 — Hs) + D ]
where H is the source height:
H = J ’2feetforcars
S 8 feet for trucks
2. If a calculator is not available, use Nomograms B1 and B2. Worksheet B
may be used to record the procedure, which is as follows:
STEP 1 Enter Nomogram Bi with and HB_HO to obtain the quantity a.
STEP 2 Enter Nomogram B2 with DH and HB to obtain the quantity b. Obtain
separate values for cars and trucks. Note that H 5 is not needed, as it is
built into the nomogram, and that there are separate scales for cars and trucks.
STEP 3 Enter Nomogram B2 with D and H 0 to obtain the quantity c. Obtain
separate values for cars and trucks.
STEP 4 Compute 6 for cars and trucks:
8 a +b — c
Note that a, b and c are related to, but not the same as, the distances
A, BandC.
The calculated value of 6 is always positive. However, because shielding for
a given value of 6 depends on whether the direct tine of sight (C in Figure 8—2) is broken,
the following sign convention is adopted:
85
-------
• 6 is positive if line of sight C is broken by the barrier.
• 8 is negative if line of sight C is not blocked by the barrier.
Whether or not line of sight is blocked may be determined from the geometry. Altema-
tively, Nomogram B3 may be entered with H 0 and DO/DH to obtain Hcriti the critical
barrier height which just touches the line of sight. If HB> Hcrit 6 is positive. If
HB < Hi i 6 is negative.
STEP 5 Enter Nomogram B4 with the barrier half angle o and each value of 6
to obtain the barrier factors.
If a finite barrier is not symmetric, divide the road into two segments
at 8 B = 0 and treat as two separate roads.
STEP 6 Multiply the car and truck volumes in each lane by the corresponding
barrier factors. Add these over all lanes to obtain the adjusted traffic
volume Q’. Sum the values (volume times barrier factor) for trucks to
obtain the adjusted truck volume 1’.
STEP 7 Follow the procedure of Appendix A, using Q’ and 1’ in place of Q and 1.
When obtaining D from Nomogram A3, use the “free space” scale.
B6
-------
REQUIRED DATA
WORKSHEET B
BARRIER NOMOGRAM PROCEDURE
(See Text for Step—by—Step Instructions)
STEP 2
STEP 3
Horizontal Distance from Observer to Barrier,
Horizontal Distance from Barrier to Center of
Nearest Lone
Total Distance from Observer to Center of Nearest
Lane (D 0 °H
Barrier Height, Relative to Rood Surface,
Observer Height, Relative to Road Surface,
Barrier Included Half—Angle
FIB_HO _______ft
a
bc
bT
CC
CT
a
=
=
= ft
__________ ft
— __________ ft
____________ degrees
D 0
ca
lf H > H . ,then ô Is positive, else Is negative
B CIItCAR
If H > H , then 6 T is posItives else 6 T Is negative
B crItTRUCK _____________ }Clrcle the
6 C +___________ 6 T Appropriate Signs
STEP 5
Barrier FdCtOfc =
Barrier FactorT
STEP 7
T’ (T ____________ x (Barrier FactorT ____________) __________
($rucks/hour) (from STEP 5)
Proci.d to Nomogrom Procedure In Appersdi* A using Q’ and T’ for Q and T, respectively.
B7
ft
ft
D
MB
H 0
STEP 1
STEP 4
• (a __________) + (b — __________) (c — — ____________ it
(from STEP 1) from STEP 2) (from STEP 3)
( • )+(b 1 - )_(cT = ) ________F ’
(from STEP 1) (from STEP 2) (from STEP 3)
H —
_________ cr CAR
H
cit =
TRUCK
STEP 6
(Q ____________) x (Barrier Factor = ) __________
(total vehicles/br) (from STEP 5)
-------
900
BOO
700
600
500
400
50
300 40
30
200
20
100 15 1.0
90
80
70 10
60
50 7 0.5
6
40
5
30. 4
20
2
10 10.1
D
F1 8 -H 0
EnterwHh D 0 and HB — H 0
•0=0
Exitwitha.
Equation: see text
C
Barrier Nomogram Bi. Calculation of the Quantity “a”.
B8
-------
1000
9001 r
800
3 00
600
500 5
400
50—i , . .
300 40 1— 50
200 3QI _40
30
100 Cars 25 Trucks
1.0
15
90
80
70 20
19
60 tO 18
50 9 17 0.5
40 8 16
15
30 6 14
5
20
4 12
10 0.1
3 11
D
0.05
Enter with DH and HB. 2 • 5 HB
Exit with bc and b 1 .
H 0
Enter with D and Hd 0.02
b
Exit with CC and c 1 . Equation: see text
II , .. SI
Barrier Nomogram B2. Calculation of the Quantities “b” and
B9
-------
Cars
-4-
—2—
4
227 3o
6
20 25
0
8
18
26
2
10
16
24
4
12
14
22
6
14
1
20
Trucks
Cars
TrucI
8
16
10
18
10
18
16
12 20
6 14
14 22
4 12
24
o
18
26
8
20 —28
22 30
H
o
6
.414
H.
crit
D
Enter with H 0 (on car scale) and —2.
H
Exit with H for cars.
crit D
Enter with H 0 (on truck scale) and
Exit with Hit for trucks.
Equation: see text
Barrier Nomogram B3. Calculation of the Quantity H.p.
BlO
D 0
DH
Ic
-------
-0.04
Equation:
No simple equation exists
Enter with OBand ö .
Exit with Barrier Factor (car).
Enter with OBand 61.
Exit with Barrier Factor (truck).
Barrier Nomogram B4 0 Calculation of Barrier Factor.
.07
Barrier
Half
Angle, 6 B
.09
S.
Borr e
Fe ctor
a
sd
0.4
0.5
0.6
a
0.7
-0.1
C. S
—0.2
—0.]
—0.5
0.9
LO
Bit
-------
APPENDIX C
Computerized Highway Noise Models
There are presently three highway noise models available as computer programs
which are employed by Federal agencies. These are the NCHRP,Cl TSCC 2 and RDGC 3
models, used by the Federal Highway Administration (FHWA). In addition, Wyle
Laboratories has developed a computerized highway noise model for use in environ-
mental planning which we will call the Wyle model.
NCHRP Model
This model was originally designed as a series of nomograms and charts;
however, a computerized version is currently available from FHWA. Themodel pre-
dicts L 50 and L 10 noise levels, at a given point, due to one or several highways.
The levels are based on calculations from a semi—empirical traffic noise model. Data
requirements for this model are:
• Traffic volume, speed, and percentage of heavy vehicles.
• Highway locations, elevations and/or depressions, and gradients.
• Highway surface roughness.
• Location of traffic controls.
• Highway width (number of lanes).
• Receiver locations.
• Barrier locations and geometry.
The basic calculation of the program is for L 50 from each highway. L 10 is then
obtained from L 50 by applying adjustments based on the statistics and geometry of the
traffic flow. Due to limitations in the statistical model, calculations for low truck
volumes or interrupted flow may be of questionable accuracy. The combination of
several highways of similar noise output, or the presence of barriers, in certain cases,
may also reduce the reliability of the L 10 calculation.
Cl
-------
TSC Modd
This model can handle the same multiple road and complex barrier configurations
as the NCHRP model. The basic calculation is in terms of Leq? however, which allows
predictions to be accurate for low traffic volumes and complex road configurations. In
addition to Leqi the program also computes 110 1 L5 J L 90 , 1 NP , and A—weighted
octave band levels. The statistical metrics are obtained by applying theoretical adjust—
ment to ‘eq The accuracy of the statistical metrics is decreased in complex situations,
although not so much as with the NCHRP model because of the reUability of the basic
L calculation. The basic input data is similar to that for the NCHRP model, with the
eq
addition of topography and ground surface acoustical properties. All locations must be
specified in three—dimensional Cartesian coordinates, which can make input data quite
lengthy.
This model allows for reflection of sound from surfaces, and includes a calculation
of ground attenuation. The ground attenuation model is extremely crude, however, and
must be regarded as approximate. Individual vehicle noise levels fcmi the basis of the
Leq calculation. The user has the option of specifying vehicle noise levels other than those
provided with the program.
Revised Design Guide (RDG) Method
The Revised Design Guide is a composite product of the NCHRP and the TSC
prediction methods — the two methods authorized by the Federal Highway Administrotion
for use on Federal—aid highway projects. The Revised Design Guide (RDG) supplements
these Iwo authorized methods with experimental data and additional mathematical
structuring to extend the prediction validity to low—volume traffic situations.
In brief, the RDG structure consists of an L 10 ncrnogram (similar to the TSC nomogram
but with revised vehicle source data and revised distance Correction), a barrier nomo—
gram, and a series of worksheets — all leading to a hand—method calculation for simple
roadway geonietrics. As a partner to the hand method, the RDG includes a computer
program (similar to the TSC program but with revised source levels, variable propagation
drop—off, revised low—volume mathematks, segnent adjustment and many other factors)
for the detailed prediction of roadway noise levels, both For complex roadway geometrics
F ioise Pollution LeveT
C2
-------
and for detailed barrier design. In addition, this computer program contains a diagnosis
capability that pinpoints “hot spots” along the roadway and enables the user to balance
any barrier design up and down the roadway, to avoid under— or over—design of expensive
roadway barriers.
Wyle Model
This program takes a different approach from the NCHRP and TSC models in that
only one straight road is consider d, but detailed lane and traffic information may be
specified ?tCurved and/or multiple roads can be accounted for through usage of the
nomogram method described in Appendix A. The program is written in Super Basic, a
conversational language, and is designed to be used with a minimum of instruction.
Taking advantage of the conversational Formal, “full” and “simple” versions are incor-
porated into the same program. After requesting the number of lanes, lane width, and
median strip width, the program requests traffic information. The Following data may be
supplied in either a full or a short form:
• Traffic flow and truck mix: lane by lane, or one total for each direction.
• Speeds: by lane and vehicle type, or one speed For each direction.
• Vehicle noise levels: values may be specified for up to four vehicle types, or
use values for cars and trucks ‘in program.
The noise level is calculated in terms of L for specified distances from the
eq
highway. The ground attenuation may be specified in terms of a number of dB per doubling
of distance from the highway. This form of grcund attenuation loss is a good approximation
for distances up to several hundred feet. After running the program, any or all of the input
data may be changed at the user’s option to test different cases.
Comparison of the Models
In using the noise models described above, ft may be found that different models
often- provide different values of the noise level. This is due to differences in the way the
computation is performed. There is no simple factor that can be applied to relate the noise
levels computed by the various models because the differences are strongly dependent on
the highway conditions. A detailed comparison of the three models has been made in
Reference C7. A series of charts are presented which may be used to estimate differences
among the three models for any specific case.
C3
-------
REFERENCES FOR APPENDIX C
C 1. Grove, G . H., “Traffic Noise Level Predictor Computer Program,” Research
Report No. R—942, Michigan State Highway Commission. October 1974.
C2. Kurze, UJ., Levison, W.H,, and Serben, S., “User’s Manual for the
Prediction of Road Traffic Noise Computer Programs,” U.S. Department of
Transportation Report DOT—TSC—315—1, May 1972.
C3. Revised Design Guide: ref: Kugler, B.A., Commins, D.E., and Galloway,
W.J., °Design Guide for Highway Noise Prediction and Control,” Bolt,
Beranek and Newman, Inc., Report 2739 (to be published).
C4. Plotkin, K.J., “A Model for the Prediction of Highway Noise and Assessment
of Strategies for Its Abatement Through Vehicle Noise Control,” Wyle Research
Report No. WR 74-5, for the U.S. Environmental Protection Agency,
September 1974.
C5. Gordon, C.G., Galloway, W.J., Kugler, B.A., and Nelson, D.L., “Highway
Noise — A Design Guide for Engineers,” NCHRP Report 117 (1971).
C6. Kugler, B.A. and Pierson, A.G., “Highway Noise—A Field Evaluation of
Traffic Noise Reduction Measures,” NCHRP Report 144 (1973).
C7. Plotkin, K.J. and Kunicki, R.G., “Comparison of Highway Noise Models,”
Wyle Research Report No. WR 76—25, for the U.S. Environmental Protection
Agency, May 1977. Also, EPA Report 550/9-77-355.
C4
-------
APPENDIX D
The Effect of Motor Vehicle Noise Regulations
On Highway Noise Levels
The method of computation described in Appendix A is based upon the existing
noise levels produced by automobiles and trucks. In the future, these levels will
undergo a change as a result of vehicle emission regulations promulgated by EPA.
At the moment, there are two such regulations, both relating to medium and heavy
frucks. The first limits the noise produced by trucks as they operate on the highway,
and is expected to hove the effect of reducing the average 50—foot pass-by truck noise
level about 2 dB by mid—1977, assuming 95 percent compliance with the regulationP’
The second regulation limits the noise emissions of newly manufactured trucks, and
will result in gradual reductions as older trucks are retired from service and replaced
With new ones.
The effect of these changes on highway noise levels can be estimated. At the
moment, 50—foot pass—by truck noise levels are between 15 and 19 dB greater than
automobile noise levels? 2 Due to this dominance of truck noise, the reduction in
highway n&se levels due to reduced truck vehicle noise levels will be cçproximately
as shown in Table Dl for speeds less than 35 mph.
Table Dl
Reduction in Highway Noise Level
Versus Reduction in 50-foot Passby Level
Reduction in
Average 50—foot Passby
Truck Noi5e Level from
January 1976 Level
(dB)
Approximate Reduction In
Highway Noise Level
(L or L )
eq dn
Truck Mix
5%
10%
20%
2
4
6
1.5
2
4
2
3.5
5
2
3.5
5.5
Dl
-------
The appropriate U.S. Environmental Protection Agency Regional Office should
be consulted — prior to the use of Table Dl — to determine the proper 50-foot noise level
reduction achieved at the time. At higher speeds, the reduction in average noise level is
generally 1 dB or less. Thus, by maintaining current information on average truck noise
levels, one can develop an additional negative correction accounting for quieter future
vehicles which will allow use of the nomogram and screening methods well into the
future.
It should be noted that as highway noise levels are reduced through more
stringent regulations, FHWA is expected to revise their design level standards accordingly.
Thus, the necessity for noise abatement measures will, in the future, remain of vital
importance in the planning and design of our nation’s highways.
D2
-------
REFERENCES FOR APPENDIX D
Dl. Plotkin, K.J., “A Model for the Prediction of Highway Noise and Assessment
of Strategies for its Abatement Through Vehicle Noise Control “, Wyle Research
Report WR 74-5, for the U.S. Environmental Protection Agency, September 1974.
D2. Ptotkin, K.J., and Sharp, B.H., “Assessment of Highway Vehicle Noise Control
Strategies”, presented at Inter—Noise 74, Washington, D.C., October 1974.
D3
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