Field characterization of urban road traffic noise sources: effects of road class and vehicle composition

Routine road traffic noise assessment describes the source by traffic volume, speed and vehicle-category shares, whereas monitoring usually reports a measured source-side level with a total vehicle count only, so that the operating conditions behind that level remain unidentified. This paper addresses that gap with a multi-city field study of 25 urban road sections in Guangzhou, China, covering four road classes and three operating periods. Each section-period was measured three times for 20 min with Class 1 instrumentation and counted by vehicle class, giving 75 observations analyzed with an explicit metrological and statistical treatment. Levels ranged from 58.5 to 79.8 dB(A); arterial sections alone spanned 15.0 dB(A) and night-time measurements 21.3 dB(A). Vehicle-class flow was more strongly associated with L A e q than average speed, medium-vehicle flow showing the strongest association ( r = 0.867, 95 % CI 0.797-0.914). The expanded uncertainty of a single level was about 0.8 dB ( k = 2). The results support recording vehicle-class counts alongside L A e q , so that a measured level can be attributed to traffic volume, fleet composition or both.