Traffic composition and variability of road traffic noise levels in the vicinity of Colombo, Sri Lanka

Abstract

Abstract: A study was conducted to determine the contribution of different types of vehicles to road traffic noise levels. Measurements were carried out on three different categories of roads at six separate locations, approximately 30 km away from the city of Colombo. At each location, continuous noise measurements were taken for a duration of 13 hours on weekdays and several key noise level descriptors (Leq, L10, L50, L90) were measured simultaneously. It was observed that A-weighted equivalent noise level (Leq) along main roads and secondary roads reached ~70 dB(A), which is the maximum permissible noise level prescribed for road traffic by Japan for residential areas. Similar to previous studies, a linear correlation was observed between Leq and other noise descriptors. Specially L10, which can be related to annoyance, can be estimated with an accuracy of ± 1 dB(A) by measuring Leq. The correlation between the rate of vehicle flow and the measured noise level showed a logarithmic relationship. It is shown that the key noise descriptors can be estimated with an accuracy of ± 2.5 dB(A) by measuring the flow rate of vehicles. The vehicle composition showed that heavy vehicles such as lorries, buses and containers contribute significantly to the average noise levels.