Effects of traffic composition on road noise: a case study

This study uses data collected in a Brazilian city to investigate the characteristics of the noise levels as related to road traffic volume and composition. Traffic composition is defined as the percentage of heavy vehicles with respect to the total number of vehicles. Measurements were made from Monday to Friday, 6:00-10:10 a.m. A total of 149 measurements were made on three roads. For each, the percentile level and the noise equivalent level were measured. These levels were plotted against the composition of the traffic and empirical expressions were obtained with reasonably good correlation indexes. The results are compared to those that Compton and Gilbert found for UK roads. The findings in the Brazilian study may be due to higher noise levels generated by vehicles in Brazil compared to those in Britain. This variation is attributable to comparatively poor maintenance of the vehicle fleet, non-standardization of the exhaust system position and the driving habits of Brazilian drivers.