A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Transportation Engineering

Thesis (Ph. D.) - Asian Institute of Technology, 2025

Introduction: Unsignalized mid-block crosswalks can often lead to conflicts between motorcyclists and pedestrians, especially in Thailand which has a high number of motorcycles using the road system. Generally, motorcyclists must yield to crossing pedestrians. However, many pedestrian-motorcycle crashes occur due to motorcyclists failing to stop or yield. This risky decision on the part of motorcyclists is caused by too short gap acceptance, which can cause injury or death to both the motorcyclist and pedestrian. This study aims to investigate motorcyclists{u2019} critical gap when faced with pedestrians crossing at unsignalized mid-block crosswalks and to determine the significant factors that influence motorcyclists{u2019} decision to pass unsignalized mid-block crosswalks. Method: The critical gap was estimated using Raff{u2019}s Method, Wu{u2019}s Method, and binary logistic regression, while the influencing factors for motorcyclists{u2019} decision were analyzed using the binary logistic regression model. Results: From the results of this study, the critical gaps of motorcyclists when faced with a single movement of a pedestrian are very short (0.54-1.07 seconds). Factors that influence motorcyclists{u2019} whether to stop at crosswalks were found to include headway time, direction of pedestrians{u2019} movement, presence of vehicles nearby, pedestrian crossing locations, number of crossing pedestrians, and crosswalk colors. The interaction effect between crosswalk colors and the type of median was also significant to the model. Conclusions: The short critical gap reflects the risky behavior of motorcyclists in Thailand. To improve the safety of motorcyclists and pedestrians, the findings of the present study are very important to improve law enforcement and the geometric design of unsignalized mid-block crosswalks.