Safety effects of paved shoulder width on a four-lane divided rural highway in India: A matched case-control study.

• The paved shoulder reduces the risk of fatal crashes. • The effect of paved shoulder width on the safety of VRUs, especially M2W users, has been assessed. • Paved shoulder improves the safety of M2W users and slow-moving vehicles on multilane highways. • The paved shoulder has limited safety benefits for rear-end only fatal crashes. • The matched case-control method is an effective viable safety evaluation method in limited crash data availability, as in LMICs. Research has revealed the safety benefits of shoulder improvements on highways are significant. The study aimed to assess the impact of paved shoulder width on the frequency of fatal crashes in case of heterogeneous traffic on a rural four-lane divided highway in India. A matched case-control design was employed to evaluate the safety effectiveness of the paved shoulder width on fatal crashes. The impact of shoulder widths on victims of motorized two-wheelers (MTW) users, slow-moving vehicles and rear-end fatal crashes were also analyzed. The study stretch was divided into segments of 100 m. Each segment was linked to the traffic volume, speed, geometric characteristics, and roadside hazards characteristics. Analysis of the crash data revealed that 39% of the total crashes are due to rear-end collisions, mostly occurring at nighttime. The model results are interpreted concerning segments with no shoulder as the baseline category. Model results suggest that paved shoulder has safety benefits for all road users up to 1.5 m shoulder width. The provision of paved shoulders reduced the risk of all fatal crashes and improved the safety of pedestrians and slow-moving vehicles. However, the safety of MTW users reduced on segments having paved shoulder width more than 2 m. Also, segments with a paved shoulder width of more than 1.5 m have a higher risk of rear-end fatal crashes than no shoulder segments. This study findings have a direct bearing on the geometric standards recommended by the road authorities in India. [ABSTRACT FROM AUTHOR]