Improving roadside design policies for safety enhancement using hazard-based duration modeling.

Area of Science:

• Traffic Safety Engineering
• Transportation Research
• Accident Analysis

Background:

• Roadway departure (RwD) crashes, including run-off-road (ROR) and cross-median collisions, are highly lethal, causing 53% of US traffic fatalities (2014-2016).
• Driver inattention, fatigue, and avoidance maneuvers contribute to leaving the travel lane, with roadway geometry playing a critical role in crash outcomes.

Purpose of the Study:

• To investigate the distance traveled by errant vehicles in run-off-road (ROR) crashes.
• To analyze stopping hazard rates and associated risk factors using a hazard-based duration model.
• To provide empirical evidence for the suitability of the Cox proportional-hazards model in ROR crash analysis.

Main Methods:

• Utilized five years (2010-2014) of roadway departure crash data (overturns, fixed-object crashes) from the Federal Highway Administration's Highway Safety Information System.
• Applied a hazard-based duration model, specifically the Cox proportional-hazards model, to analyze vehicle travel distances in ROR crashes.

Main Results:

• Over 50% of vehicles in ROR crashes traveled 36 ft. or less; 25% traveled at least 78 ft.
• Seasonal, roadway, crash, vehicle, and driver characteristics significantly influenced the distances traveled by errant vehicles.
• The Cox proportional-hazards model proved appropriate for analyzing ROR crash distances.

Conclusions:

• The study offers methodological and empirical support for using the Cox proportional-hazards model in ROR crash research.
• Findings provide valuable data for traffic agencies to enhance roadside design policies and create more forgiving roadside environments.