NOISE IMPACTS OF COMPLEX ROAD STRUCTURES IN URBAN AREAS

Abstract

Road traffic noise remains a primary environmental concern in densely populated urban areas, particularly where complex road infrastructure, such as elevated expressways, coexists with at-grade roadways. This study examines the acoustic characteristics of traffic noise in such a configuration, using the Burapha Withi Expressway over the Bang Na–Trat Road as a case study. Environmental noise measurements were conducted using one-third-octave band frequency analysis to characterize the spectral content of traffic-related sound and to assess the contribution of low-frequency components associated with structural vibration of the elevated roadway. The results indicate that sound emissions from traffic on the underlying Bang Na–Trat Road dominate the sound pressure levels measured at nearby residential receptors, exceeding the contribution from traffic on the elevated expressway. Spectral analysis shows that the acoustic environment is primarily governed by mid-frequency components, with a pronounced peak around 1,000 Hz, corresponding to typical vehicle operating mechanisms. In contrast, low-frequency noise associated with structural vibrations of the elevated expressway, observed at approximately 64 Hz, exhibits substantially lower sound pressure levels and does not significantly affect the overall equivalent continuous sound level (Leq). These findings suggest that, in complex road systems, noise mitigation strategies should prioritize controlling ground-level traffic sources rather than elevated expressways. The study provides practical insights for urban noise assessment, infrastructure design, and environmental noise management in complex roadway environments.