A two-dimensional traffic conflict measurement for assessing the safety of light mobility vehicles

• This study proposed a 2D-TTC approach to better suit LMVs’ safety applications • A case study was conducted in an urban midblock • 2D-TTC had a better traffic conflicts and crashes relationship compared to TTC • Bicycles were more often involved in potential rear-end and sideswipe conflicts • Two-dimensional kinematic data are important for assessing traffic conflict Light Mobility Vehicles (LMVs) are vulnerable road users due to limited protection and low stability. Understanding their rear-end and sideswipe crash risks is crucial for designing effective safety interventions. To assess the crash risks, a two-dimensional Time to Collision (2D-TTC) approach has been developed. Nevertheless, the existing equation was impractical in LMV-related situations. This study aims to develop a 2D-TTC approach to more effectively suit LMVs’ safety applications. A case study was conducted at an urban mid-block location in Melbourne, Australia. Extreme Value Theory was employed to model the relationship between traffic conflicts and crashes. 2D-TTC and Time to Collision (TTC) thresholds were also identified. The case study results showed that 2D-TTC approach had a closer traffic conflict-crash relationship compared to the traditional TTC function. The findings also indicated that bicycles were more frequently involved in rear-end and sideswipe conflicts compared to motorcycles and e-bikes. This study demonstrated the importance of considering two-dimensional kinematic data for assessing traffic conflicts of LMVs. Future practical applications with a larger dataset may provide insights for the use of 2D-TTC for assessing traffic safety, reinforcing LMV users’ awareness of minimum safety gaps when following a leading vehicle and promoting LMV’ warning systems.