Computer Simulations of Highway Traffic and Associated Noise Levels

Abstract

A set of computer programs has been developed that provides the capability to simulate highway traffic and to calculate the associated noise levels. Extensive measurements of vehicular noise have been classified and averaged to produce characteristic spectra for passenger cars, heavy trucks, motorcycles, and other classes of vehicles. These spectra are used to represent the contribution of individual sources along a roadway. Sources are arrayed across multiple lanes to satisfy a stated proportion of cars, trucks, and other types of vehicles, as well as specified vehicle flow and speed. The individual contributions are adjusted for the effects of source—observer distance, air attenuation, vehicle speed, etc., and summed to produce a sample spectrum. Sets of these sample spectra can then be processed by computer to yield dBA values and statistical summaries of these values, or they can be utilized in the same fashion as measured data to determine noise levels adjacent to a highway. [Work performed as a part of Highway Research Board Project NCHRP 3–7.]