An Exploratory Analysis on Fatalities of Roadway Departure Crashes

Document Type

Conference Proceeding

Publication Date



Roadway departure is considered as a top priority emphasis area within the Strategic Highway Safety Plan by the American Association of State Highway and Transportation Officials. More of half of total fatalities and significant number of injuries as well as property-damage-only crashes are occurring annually because of roadway departure crashes. The economic losses due to roadway departure crashes are enormously high for the society. Realizing the gravity of this problem, safety professionals, highway designers, planners, and policy makers need to work collaboratively to reduce the frequency of fatalities on the national highways. Due to differences in geometry, traffic, environment and driving behavior, safety performance of these functional classes of roadways varies. With that mind, this study investigated the contributing factors that led to fatalities of roadway departure crashes in rural and urban functional classes based on the national crash and traffic database. This study explored a set of tobit models for rural and urban principal arterials, minor arterials, collectors, and local roads. Within the tobit modeling framework, fatalities per million vehicle-miles-traveled, as continuous variable (left censored at zero), was estimated by functional classes of roadway to recognize the variability in the design standards. As such, a data-driven approach for roadway departure crashes by functional classes of roadway unveils the complex interaction of traffic, traffic speed, roadway, temporal and environmental characteristics, driving behavior, and crash types. A proper understanding of the contributing factors resulting from the underlying data will provide a basis to formulate pragmatic countermeasures for state and local jurisdictions with a specific focus on a Strategic Highway Safety Plan.

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Citation / Publisher Attribution

Presented at the First International Roadside Safety Conference on June, 2017 in San Francisco, CA.