Optimal seat occupancy rate of customized bus services considering in-vehicle infection risk cost during public health emergencies

Customized bus (CB), offering personalized routes and reserved seat arrangements, meets the diverse travel needs of passengers. However, the usage of public transit drops significantly during public health emergencies due to concern of in-vehicle infection risk. To enhance the competitiveness of CB during public health emergencies by raising profits and maintaining rational in-vehicle infection risk, this study proposes a bi-level seat occupancy rate optimization model which integrates the Wells-Riley (W-R) equation to measure in-vehicle infection risks. The upper-level model optimizes seat occupancy to maximize profit while penalizing the total expected number of infected CB passengers after traveling. The lower-level model is a logit mode choice model considering infection risk cost. Numerical examples are conducted to explore model properties. Results indicate that while shorter average travel route is generally considered beneficial, longer average CB travel route can actually help control in-vehicle infection rates in certain circumstances. Moreover, during severe outbreaks, the risk of infection during travel does not necessarily increase with the severity of the outbreak, because passengers tend to place a greater emphasis on personal protection. Furthermore, the result suggests that optimizing CB seat occupancy rate is essential in the context of epidemic prevention and control. Additionally, results indicate that when the performance of bus services is relatively good, CB has potential for profit growth during public health emergencies.