Sidewalks, crosswalks and lighting reduce crashes more effectively than fixed geometric road design attributes: Study

Road traffic crashes remain a significant global issue, with more than 1.19 million fatalities and millions more injured annually. The World Health Organization (WHO) has set a target to halve these deaths and injuries by 2030, emphasizing the need for a holistic approach to road safety.

While road design improvements, such as pedestrian crossings, are critical in enhancing safety, understanding the complex interactions between road attributes and traffic conditions is often overlooked.

To address this gap, researchers from Incheon National University, led by Assistant Professor Wookjae Yang, conducted a study examining how different road design elements and traffic conditions interact to affect the likelihood of crashes.

Using data from a 68-kilometer segment of a national highway in South Korea, the team applied principal component analysis (PCA) and piecewise structural equation modeling (PSEM) to examine both direct and indirect effects of road attributes on two major crash types: head-on and run-off crashes.

This study is published in the Journal of Safety Research.

The team categorized road attributes into three principal components: PC1 (pedestrian and roadside facilities), PC2 (cross-section and intersection conditions), and PC3 (road surface and curvature conditions).

“Unlike prior studies that treated traffic speed and volume as static control variables, our study considered them as mediating factors—highlighting how road conditions affect crashes not just directly but also through their influence on traffic behavior,” explains Dr. Yang.

The results showed that PC1 had the most substantial direct effect on crash outcomes, particularly for run-off crashes.

“Elements such as sidewalks, street lighting, and pedestrian crossings—which are comparably easier to modify during maintenance—proved more influential in reducing crashes than fixed geometric elements established at the design stage,” adds Dr. Yang. Inadequate pedestrian and roadside facilities were associated with higher vehicle speeds, indirectly increasing the likelihood of both crash types.

In contrast, PC2 and PC3, which include design features such as intersections, lane width, and curvature, did not show significant direct effects on crash frequency. Researchers suggest this may be due to the relatively uniform standards followed in national highway segments, leaving limited variation in these features across the study sample.

However, both components did exert indirect effects through speed and volume, reinforcing the idea that safety outcomes are shaped by the interaction of multiple factors rather than any single design attribute.

The study offers practical implications for transportation agencies and policymakers. It suggests that road safety strategies should prioritize modifiable operational features, such as pedestrian infrastructure and roadside objects, which can be adjusted post-construction to improve safety.

Furthermore, refining global road assessment tools such as the International Road Assessment Program’s (iRAP) to separate fixed geometric features from alterable operational elements may lead to more targeted and cost-effective safety interventions.

Overall, these findings contribute to a more nuanced understanding of crash dynamics and emphasize the value of context-sensitive design and maintenance approaches. “By demonstrating the mediating role of traffic volume and speed, and highlighting the stronger influence of pedestrian and roadside facilities over fixed design features, the study offers actionable insights for more effective road safety interventions,” concludes Dr. Yang.