Conflict-Based safety evaluations at unsignalized intersections using surrogate safety measures

Area of Science:

• Traffic Engineering
• Road Safety Analysis
• Transportation Science

Background:

• Traditional road safety assessments often rely on historical crash data, which may not fully capture the dynamic interactions leading to accidents.
• Surrogate safety measures, including temporal, spatial, and kinematic indicators, offer a more nuanced understanding of road user behavior and potential hazards.
• Unsignalized intersections in mixed traffic environments present complex safety challenges due to diverse vehicle types and behaviors.

Purpose of the Study:

• To develop and apply a methodology for assessing road safety at unsignalized intersections under mixed traffic conditions.
• To quantify critical conflicts using surrogate safety measures like post encroachment time (PET) and time to collision (TTC).
• To identify key factors influencing crossing and rear-end collision risks.

Main Methods:

• Utilized post encroachment time (PET) for crossing maneuvers and time to collision (TTC) for rear-end collisions.
• Calculated critical conflicts based on critical speed derived from braking distance.
• Employed generalized linear regression for modeling crossing conflicts and k-means clustering for rear-end maneuver severity.
• Analyzed data from five unsignalized intersections in urban mixed traffic settings.

Main Results:

• Motorized two-wheelers (MTWs) and cars were associated with the highest proportion of critical conflicts, particularly with right-turning vehicles.
• Traffic volume and vehicular composition were significant predictors of crossing conflicts.
• A time to collision (TTC) threshold below 1.15 seconds indicated high-risk rear-end interactions.
• The presence of MTWs and cars increased the likelihood of critical crossing conflicts.

Conclusions:

• The developed conflict-based methodology provides deeper insights into road safety at unsignalized intersections compared to traditional methods.
• Traffic volume and composition are crucial factors in understanding and mitigating crossing conflicts.
• Specific vehicle types, notably MTWs and cars, require focused safety interventions in mixed traffic environments.
• The proposed safety framework is applicable for evaluating and enhancing safety at unsignalized intersections with mixed traffic.