Assessing the fluctuations in job accessibility under travel time uncertainty

The rapid pace of urbanization and population growth has led to heightened traffic congestion and extended commuting distances, consequently amplifying uncertainties in travel times. For decades, studies have employed average or median travel time to assess job accessibility while neglecting variations and uncertainty in travel time, ultimately leading to imprecise evaluations of urban job accessibility. To bridge this gap, this study investigates the temporal fluctuations in job accessibility with the Accessibility Buffer Index (ABI), which measures the proportionate reduction in accessibility when the transport system fails to operate optimally. Gathering speed data at the street level in Beijing from January to June 2022, we utilize the cumulative-opportunity model with three distinct travel budgets (15 min, 30 min, and 45 min) to finely estimate daily job accessibility in spatiotemporal detail. Our findings reveal significant spatial heterogeneity in job accessibility and ABI, highlighting notable disparities in their spatial distribution. Through the use of ABI, our study offers valuable empirical evidence regarding the characteristics of accessibility fluctuations, thereby presenting a novel perspective to enhance sustainable and reliable urban transportation.