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Federal Highway Administration's Traffic Noise Model (FHWA TNM®), Version 1.0 - Technical Manual

Final Report February 1998



Prepared for
U.S. Department of Transportation
Federal Highway Administration
Office of Environment and Planning
Washington, DC 20590

Prepared by
U.S. Department of Transportation
Research and Special Programs Administration
John A. Volpe National Transportation Systems Center
Acoustics Facility
Cambridge, MA 02142-1093


This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof. This report does not constitute a standard, specification, or regulation.

The United States Government does not endorse products or manufacturers. Trade or manufacturers' names appear herein solely because they are considered essential to the object of this document.


This Technical Manual is for the Federal Highway Administration's Traffic Noise Model (FHWA TNM®), Version 1.0 -- the Federal Highway Administration's computer program for highway traffic noise prediction and analysis. A companion User's Guide describes how to use TNM [Anderson 1998]. In addition, a companion technical report documents the vehicle noise-emissions data base [Fleming 1995].

Overview of TNM: TNM computes highway traffic noise at nearby receivers and aids in the design of highway noise barriers. As sources of noise, it includes 1994-1995 noise emission levels for the following cruise-throttle vehicle types:

Noise emission levels consist of A-weighted sound levels, one-third octave-band spectra, and subsource-height strengths for the following pavement types:

In addition, TNM includes full-throttle noise emission levels for vehicles on upgrades and vehicles accelerating away from the following traffic-control devices:

TNM combines these full-throttle noise emission levels with its internal speed computations to account for the full effect (noise emissions plus speed) of roadway grades and traffic-control devices.

TNM propagates sound energy, in one-third-octave bands, between highway systems and nearby receivers. Sound propagation takes the following factors into account:

TNM computes the effect of intervening ground (defined by its type, or optionally by its flow resistivity) with theory-based acoustics that have been calibrated against field measurements. In addition, TNM allows sound to propagate underneath selected intervening roadways and barriers, rather than being shielded by them.

During calculation, TNM perturbs intervening barriers up and down from their input height, to calculate for multiple heights. Then during acoustical design of selected barriers, combined with selected receivers, TNM displays sound-level results for any combination of height perturbations. It also contains an input-height check, to determine if noise barriers break the lines-of-sight between sources and receivers. In addition, it provides summary cost and benefit information for each barrier design, from user-supplied unit barrier costs and land-use information.

For selected cross sections, TNM also computes the effect of multiple reflections between parallel barriers or retaining walls that flank a roadway. The TNM user can then enter the computed parallel-barrier degradations as adjustment factors for individual receivers in TNM's calculation of receiver sound levels.

TNM computes three measures of highway traffic noise:

TNM computes these three noise measures at user-defined receiver locations, where it also computes several diagnostics to aid in noise-barrier design. In addition, it computes three types of contours:

TNM runs under Microsoft® Windows Version 3.1 (or later). Within Windows, it allows digitized input using a generic Windows digitizer driver, plus the import of DXF files from CAD programs and input files from STAMINA 2.0/OPTIMA. Note: TNM will run under Microsoft® Windows 95 or Windows NT, however, TNM is a 16-bit program and will not take full advantage of the 32-bit architecture associated with Windows 95 or NT.

To aid during input and to document the resulting input and barrier designs, TNM shows the following graphical views:

TNM Version 1.0 replaces FHWA's prior pair of computer programs, STAMINA 2.0/OPTIMA. In addition, TNM's technical manual replaces FHWA's prior prediction model: FHWA Highway Traffic Noise Prediction Model, FHWA-RD-77-108.3

This manual documents the fundamental equations, the acoustical algorithms, and the interactive logic for all computations within the TNM. The manual is organized as follows:

Section 1. Overview of TNM: This section overviews the basic elements of the TNM's prediction model. It describes the basic concepts of the model, from vehicle noise emissions to predicted sound levels.

Section 2. Model Description:This section describes the TNM's prediction model in more detail, with references to the manual's appendixes for detail on algorithms and mathematics. In particular, this section describes:

In addition, this manual contains the following detailed appendixes:

Appendix A. Vehicle noise emissions;

Appendix B. Vehicle speeds;

Appendix C. Horizontal geometry and acoustics;

Appendix D. Vertical geometry and acoustics;

Appendix E. Parallel barriers;

Appendix F. Contours;

Appendix G. Model verification;



FHWA TNM® was developed in part by:

U.S. Department of Transportation
Federal Highway Administration

Robert Armstrong, Steven Ronning, Howard Jongedyk.

U.S. Department of Transportation
John A. Volpe National Transportation Systems Center, Acoustics Facility

Overall management, emission-data design/measurement/analysis, propagation-path development, program testing, User's Guide, Technical Manual, TNM Trainer CD-ROM:

Gregg Fleming, Amanda Rapoza, Cynthia Lee, David Read, Paul Gerbi, Christopher Roof, Antonio Godfrey, Shamir Patel.

Harris Miller Miller & Hanson Inc.

Technical management, emission-analysis design, functional requirements, conceptual program design, acoustical algorithms, design/development/testing of acoustical code and vertical geometry, User's Guide, Technical Manual:

Grant Anderson, Christopher Menge, Christopher Rossano, Christopher Bajdek, Thomas Breen, Douglas Barrett, William Robert.

Foliage Software Systems, Inc.

Program design/specification/development/testing, development of horizontal geometry and interfaces, program documentation:

Ronald Rubbico, George Plourde, Paul Huffman, Christopher Bowe, Nathan Legvold.

Special contributors:

Vanderbilt University: William Bowlby -- emission-data design/measurement/analysis, vehicle speeds.4
Bowlby & Associates, Inc.: William Bowlby -- TNM Trainer CD-ROM
Serac Technology Group, Inc.: Theodore Patrick -- TNM Trainer CD-ROM
University of Central Florida: Roger Wayson -- emission-data design/measurement/analysis.
Florida Department of Transportation: Win Lindeman -- Funding and management of subsource-height study.
Florida Atlantic University: Stewart Glegg, Robert Coulson -- subsource height measurements.5
Maryland State Highway Administration: Kenneth Polcak -- emission data.
Ohio University: Lloyd Herman -- emission data.
Emission-data state agencies: California, Connecticut, Florida, Kentucky, Maryland, Massachusetts, Michigan, New Jersey, Tennessee.

Design and Review Panel:

Domenick Billera, James Byers, Rudy Hendriks, Harvey Knauer, Win Lindeman, William McColl, Kenneth Polcak.

National Pooled-Fund Contributing States:

Arizona, California, Florida, Georgia, Hawaii, Illinois, Indiana, Iowa, Kentucky, Maryland, Massachusetts, Michigan, Minnesota, New Jersey, New York, North Carolina, Ohio, Oregon, Pennsylvania, Tennessee, Texas, Utah, Virginia, Washington and Wisconsin.

The development work of Harris Miller Miller & Hanson, Foliage Software Systems, Vanderbilt University and the University of Central Florida was conducted in part under contract to Foster-Miller, Inc. Vanderbilt University and the University of Central Florida were also under contract to the Volpe Center.

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