Reduction of traffic noise due to improved road conditions: evidence from Matara & Hambantota, Sri Lanka

Abstract

“Road traffic noise” is becoming a serious problem for civilians living close to roads with heavy traffic in Sri Lanka. According to the statistics of Department of Motor Traffic, Sri Lanka, the total number of registered vehicles has been increased up to 5.07 million by the end of July-2013. The increase of motor vehicles with inadequate road conditions would contribute to enhance the noise pollution. Previous studies had found that some citizens living in urban areas exposing to heavy noise have developed hearing disorders. This matter has been often overlooked in developing countries, in contrary, some developed countries which have better road conditions, have started to use materials that produce low tire noise and good sound absorption surface layers for roads. In this study, a comparison of noise level is performed before and after the improvement of road conditions in selected urban areas in southern region of Sri Lanka. All measurements were carried out before and after rehabilitation and widening of respective roads. B&K Type-2250 hand held analyser was used to measure noise level and experiments were carried out in 2013, before the rehabilitation, and 2014, after the rehabilitation, respectively. Traffic volume of the roads studied was counted manually. Noise data were recorded at distances of 200 m for Class A and 400 m for Class B roads along the sides of selected roads. A-weighted equivalent continuous sound pressure level at each location, LAeq, for 15 minutes time period was measured. An internationally recommended IMMI noise mapping software was used to map the noise distribution. Noise maps constructed before and after the rehabilitation of roads were compared. The average noise levels in the vicinity of Class A and Class B roads studied have decreased the noise level by 0.35 - 12.03 % after widening/improving the roads. The maximum drop of noise contour for Class A highway was found to be 3.5 dB or 6.2 % even with the increase of traffic volume by 61.5% during the period studied. For Class B roads a maximum of 5.8 dB or 12.0 % drop of traffic noise level was recorded. The width of the highest noise contour (having LAeq = 75-80 dB) was decreased by 74.3 % and 30.3 % for Class A and Class B roads respectively. It can be concluded that widening and improving the conditions of the roads have effectively reduced the traffic noise pollution, even though the volume of traffic has been increased. It also proves the importance of using noise maps for the development and redesign of cities as the removal of noisepollution could contribute so much to better quality of life in Sri Lankan urban cities.