Trrl Lr 752

The measurements have been used to construct approximate vehicle noise levels and speed characteristics over the speed range 20-100 km/h for up to 6 vehicle categories, and used as input in the TRRL computer model of traffic noise. By varying the number of vehicle categories in the model it was found that the lest number of categories that could be used without causing a significant change in the accuracy of prediction for urban roads was three. A comparison between measured and predicted values of L10 using the computer model with three vehicle categories at 11 urban sites showed fair agreement, indicating that accurate computer predictions of traffic noise for urban traffic conditions can be achieved by extending vehicle noise level and speed characteristics to the lower speeds typical of urban traffic conditions