A study of the ground and vegetation effects on the propagation of road traffic noise in south east Queensland

Abstract

South east Queensland's booming population is creating a range of challenges for Main Roads. Traffic volumes in the metropolitan region are increasing by an average of 3.5 percent per annum (rolling average for the past five years), contributing to an increase in road traffic noise. Road traffic noise may affect community lifestyles, so the department is keen to identify whether or not its noise calculation model is predicting higher or lower noise levels than actually occur over various ground and vegetation types. The type of ground or vegetation surface which sound (generated by traffic on a roadway) propagates over has an effect on the level of noise attenuation with increasing distance from the sources. Main Roads is interested in determining the attenuation of road traffic noise due to ground surface type, particularly for typical Australian bush. Main Roads uses a United Kingdom methodology known as CoRTN (Calculation of Road Traffic Noise) to calculate road traffic noise. This model considers attenuation due to distance. However, there may be significant differences in the level of road traffic noise attenuation between the physical environments of England's ground and vegetation types and Australia's ground and vegetation types. This research project will aim to identify whether a correction factor for the L10 (1h) and L10 (18 hour) noise descriptors is needed for CoRTN, helping to ensure the noise predictions and calculations undertaken by Main Roads are suited to south east Queensland conditions.