TNM VERSION 2.5 ADDENDUM to Validation of FHWA's Traffic Noise Model® (TNM): Phase 1

Final Report July 2004

FHWA-EP-02-031 Addendum

DOT-VNTSC-FHWA-02-01 Addendum

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, DTS-34
Cambridge, MA 02142-1093

Notice

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.

Abstract

The Volpe Center Acoustics Facility (Volpe) in support of the Federal Highway Administration (FHWA) is conducting a multiple-phase study to assess the accuracy and make recommendations on the use of FHWA's Traffic Noise Model (TNM). The TNM Validation Study involves highway noise data collection and TNM modeling for the purpose of data comparison. In 2002, Volpe completed Phase 1 of the study. For this phase, over 100 hours of traffic noise data were collected at seventeen highway sites around the country. The seventeen sites included: open areas next to the highway with acoustically soft ground (e.g., lawn); open areas with acoustically hard ground (e.g., pavement or water); and areas next to the highway with an open area behind a single noise barrier. Results indicated that TNM Version 2.0 was, on average, over-predicting when measured sound level data were not calibrated using a reference microphone, i.e., when site bias was not accounted for. This issue of over-prediction initiated the development of TNM Version 2.5, which addresses the over-prediction and also has other acoustical improvements. This addendum to the Phase 1 report includes results generated with TNM Version 2.5, where the results show TNM's improved performance.

Acknowledgments

The authors of this report wish to express their great appreciation to all involved in making the TNM Version 2.5 update to the TNM Validation Study: Phase 1 a success. We would like to specifically thank Bob Armstrong , Steve Ronning, Chris Corbisier, and Mark Ferroni of the Federal Highway Administration, Office of Natural Environment, for essential support and guidance in making this a successful study. We also wish to thank Eric Boeker, Mike Lau, Andrew Malwitz, Ben Pinkus, Dave Read, and Clay Reherman of the Volpe Center for their participation in discussions and data analysis.