Noise model for slow‐speed trucks on Baltimore city streets

Abstract

The following list outlines the essential elements in the development of a noise model for slow‐speed trucks in Baltimore, MD. (1) Measurements were made of peak passby‐noise levels and average running speeds of trucks operating on the streets of Baltimore. The noise measurement system was the General Radio Type 1981 sound level meter, with a 50‐dB dynamic range and a maximum hold capability. We also included a counting program to classify a clearly defined segment of Baltimore's truck population into one of three categories: heavy trucks (vehicles with more than 2 axles), medium trucks (vehicles with 2 axles and 6 wheels), and buses (both city and interstate). (2) Synthesize data and develop linear regression equations for the emission level (peak passby level at 50 ft) of slow‐speed heavy and medium trucks as functions of average running speed. (3) Substitute the empirical emission levels into the Transportation Systems Center computer model for the prediction of L10 (dBA) due to road traffic. The final emission level (EL) equation for heavy trucks is EL = 83.4 − 2.5 log S; for medium trucks the equation is EL = 67.4 + 5.2 log S. In both equations S is average running speed in miles per hour and 14 < S < 30. In both vehicle categories, correlation between emission level and average running speed is very low; in fact, statistical tests indicate that the correlation coefficients do not differ significantly from zero. However, we are constrained to use equations which relate emission levels to average running speed because individual truck speeds cannot be predicted for future years. [Work supported by the Interstate Division for Baltimore City.]