CLASSIFYING ROAD VEHICLES FOR THE PREDICTION OF ROAD TRAFFIC NOISE.

The accuracy of traffic noise predictions obtained using the TRRL computer model of traffic noise depends to a considerable extent on the degree of simplification adopted in categorising vehicles according to their sound output and speed in the traffic stream. This report examines and summarises the available data on the acoustic classification of vehicles in traffic streams for predicting traffic noise. Measurements of speed, noise level and vehicle type have been made in road conditions ranging from fairly congested urban situations with speeds around 20 km/h to free flow on motorways with speeds over 100 km/h. The measurements have been used to construct approximate vehicle noise levels and speed characteristics over the speed range 20-100 km/hz for up to 6 vehicle categories, and used as input in the TRRL computer model of traffic noise.