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

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.