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.
