This study investigates the influence of site effects on damage to buildings during earthquakes and analyzes the impact of collapsed street-front buildings on road network connectivity. First, a method for calculating site vulnerability (K value) using the horizontal-to-vertical spectral ratio (HVSR) of microtremors is introduced. By collecting K values and building damage data from earthquakes worldwide, an empirical relationship between post-earthquake site vulnerability (K value) and the probability of severe damage to buildings is established. Second, the probability of severe damage to buildings is converted into the probability of consequential road blockage, deriving a correlation between the K value and the probability of post-earthquake road network connectivity. A Bayesian network model incorporating four functional systems for urban seismic resilience is constructed, with the probability of road network connectivity serving as prior information. Finally, resilience indices for individual nodes and the entire urban road traffic system are calculated. Taking the Saihan District of Hohhot City as an example, microtremor observations were conducted along 41 road sections. HVSR curves derived from the recordings were used to calculate site vulnerability (K value), from which the probability of road damage was derived. The Bayesian network was then employed to compute the seismic resilience indices of the four functional systems and the overall urban road traffic system. Results indicate that the rescue system exhibits a resilience index of 51.8, and the gathering area transfer system 38.6, reflecting high seismic resilience. In contrast, the medical assistance system has a seismic resilience index of 24.7, and the material transportation system 30.3, which suggests a relatively weaker seismic capacity in these two systems. The overall seismic resilience index of the urban road traffic system is 7.69, which suggests a need for enhancement of regional seismic resilience. This method is crucial for assessing the seismic resilience of urban road networks and can provide important reference points for enhancing the seismic resilience capacity of urban infrastructure.