1. INTRODUCTION

In March 1998, the Federal Highway Administration (FHWA) released the Traffic Noise Model (TNM®), Version 1.0, a state-of-the-art computer program for highway traffic noise prediction and analysis. To provide analysts with a quick screening tool for evaluating simple highway geometries, the U.S. Department of Transportation, Research and Special Programs Administration, Volpe National Transportation Systems Center, Acoustics Facility (Volpe Center), in support of the FHWA, Office of Natural and Human Environment, developed a set of look-up tables for TNM Version 1.0. Subsequently, the FHWA, with assistance from the Volpe Center, have released multiple update packages for TNM. The latest update, TNM Version 2.5 released in April 2004, incorporated the first substantial improvements to the acoustics code. As a result, the Volpe Center has updated the TNM Version 1.0 Look-Up Tables. FHWA TNM Version 2.5 Look-Up Tables contains sound levels calculated with TNM Version 2.5 and includes an accompanying, Windows-compatible computer program to facilitate easy access to the look-up tables. This document contains the updated look-up tables in their entirety, as well as instructions on use of the accompanying computer program. Three companion reports, a User's Guide,1,2 a Technical Manual,3,4 and a data report,5 respectively, describe the use of TNM, its internal acoustics and the vehicle noise-emissions data base within TNM.

1.1 Objective

The objective of the look-up tables is to provide a reference of pre-calculated TNM results for simple highway geometries. Simple highway geometries entail sound levels propagated from an infinitely-long, straight roadway over flat ground to receivers at user-selected offset distances. All receivers are set at a height of 1.5 m above the ground. If desired, an infinitely long straight barrier may also be included. A general example of this geometry is shown below in Figure 1.

Figure 1. Example geometry.

Specifically, the tables contain results for the following parameters:

• Five vehicle types (automobiles, medium trucks, heavy trucks, buses, and motorcycles) at speeds of 0 to 130 kilometers per hour (km/h) in 10 km/h increments;^*
• Sound level propagation over acoustically hard or soft terrain;^**
• A single wall barrier (if desired) at a height of between 2 and 10 m, and located at a distance of either 10 or 30 m from the centerline of the roadway; and
• Receivers at distances from 10 to 300 m in 10 m increments from the centerline of the roadway.

^*The five TNM vehicle types are defined as follows:

• Automobiles: all vehicles with two axles and four tires -- primarily designed to carry nine or fewer people (passenger cars, vans) or cargo (vans, light trucks) -- generally with gross vehicle weight less than 4,500 kg (9,900 lb);
• Medium trucks: all cargo vehicles with two axles and six tires -- generally with gross vehicle weight between 4,500 kg (9,900 lb) and 12,000 kg (26,400 lb);
• Heavy trucks: all cargo vehicles with three or more axles -- generally with gross vehicle weight more than 12,000 kg (26,400 lb);
• Buses: all vehicles designed to carry more than nine passengers; and
• Motorcycles: all vehicles with two or three tires and an open-air driver/passenger compartment.

^**For propagation over acoustically hard ground, an effective flow resistivity of 20,000 cgs rayls was assumed; for propagation over acoustically soft ground, an effective flow resistivity of 300 cgs rayls was assumed.