Ground vibration induced by subway and bus traffic: Measurement and impact assessment

Abstract

Ground vibrations generated by urban transit systems present a growing environmental concern, adversely affecting community comfort and structural integrity. This study employs comprehensive field measurements to quantify the propagation laws and combined effects of vibrations induced by subway trains and road buses in Xi’an. Time-domain, frequency-domain, and 1/3 octave analyses reveal that bus traffic predominantly amplifies subway-induced vibration at the low frequency of 6.3 Hz. A distinct vibration amplification observed at 15 m under subway-only conditions disappeared with superimposed bus traffic, indicating an altered wave interference pattern. The resultant Z-vibration level increased significantly, exceeding the daytime limit of 75 dB within 0–15 m. These findings underscore the critical influence of multi-modal traffic and suggest that urban planners should distinguish between areas with simple and complex traffic conditions for effective vibration mitigation.