by Christopher Menge
Harris Miller Miller & Hanson Inc. (HMMH) is pleased to announce the release of TRB’s NCHRP Report 791 – Supplemental Guidance on the Application of FHWA’s Traffic Noise Model (TNM), the final product of NCHRP Project 25-34, led by HMMH and supported by a team of consultants.
Noise is an important environmental concern for highway planners and designers, and through 2010, state highway agencies have spent $5.4 billion to abate the noise generated by federally-aided highway projects. Transportation agencies assess different aspects of highway noise to determine or predict community impacts during transportation planning, although procedures have varied by program and agency. The Federal Highway Administration (FHWA)’s Transportation Noise Model (TNM) is a computer program used for predicting noise levels and their impacts in the vicinity of highways. The TNM was developed in the 1990’s by a team led by HMMH under contract to the FHWA. The FHWA has provided substantial guidance for the routine application of the TNM; however, scenarios still exist for which there remains limited or no technical guidance.
Under NCHRP Project 25-34, HMMH was asked to investigate sixteen different research topic areas to identify best practices and provide significant guidance on applying TNM to accurately, consistently, and efficiently model traffic-generated noise in a variety of settings that has not been previously addressed by TNM. The objective of NCHRP 25-34 was to supplement existing guidance on applying the TNM by identifying best practices to model structure reflected noise; bridge expansion joints; signalized interchanges; intersections; area sources (e.g., weigh stations, park and ride lots, toll facilities, and service plazas); median barriers; roundabouts; and tunnel openings. The research determines the sensitivity and accuracy of methods to model multi-lane highways, rows of buildings, topography, ground zones, and tree zones, and identifies best practices for input parameters. The research also synthesizes the state of practice for analyzing the effects of wind and temperature gradients on sound propagation.
The results of NCHRP Project 25-34 are intended for use by experienced analysts, modelers, and designers. Report 791 will be of immediate use to experienced users of TNM by helping them to improve the accuracy and precision of their modeling results and inform decision-making related to the design of noise abatement measures.