Examining the effect of relative improvements in road mobility versus accessibility on the fatality-to-injury ratio: Insights from income as an intermediate variable

Abstract

Over the past two decades, several studies have shown that the development of road infrastructure significantly reduces road crashes. However, these studies often treated all roads as a single category. In reality, roads can be classified based on their mobility and accessibility. In a recent empirical study, a U-shaped relationship was identified between the road death-to-injury (DTI) ratio and the road mobility-to-accessibility (MTA) ratio. This finding suggests that as the availability of road options increases (encompassing both high-mobility and high-accessibility roads), the DTI ratio decreases. Conversely, in situations with fewer road options, the DTI ratio tends to rise. The underlying reasoning is that more road options reduce the potential for vulnerable and less vulnerable modes of transportation to mix and interact with, improving overall safety. While prior research has examined the direct impact of MTA on the DTI ratio, there exists a gap in understanding the indirect impact of MTA to the DTI ratio. This study utilizes two-equation panel regression models to examine the direct and indirect impacts of MTA on the DTI ratio. The direct impact examines how MTA directly influences the DTI ratio, whereas the indirect impact explores how MTA impacts economic performance through export-led development and the subsequent influence of economic performance on the DTI ratio. The results of this study showed that there is a direct and indirect relationship between the MTA and the DTI ratio. The expected threshold level of the total impact of MTA, which is the sum of its direct and indirect impacts on the DTI ratio, can rise or fall depending on economic performance levels under high export-led growth conditions. The findings provide useful information about future strategies for developing road infrastructure, which can aid in achieving long-term road safety goals.