About the research
In the United States, nearly 40,000 fatal crashes occur every year, and about one-third of these fatalities involve a vehicle striking a roadside object, such as a culvert, tree, or utility pole. Culverts, specifically, are placed on the roadside to allow water to flow under a road or railroad from one side to the other. Since these are placed close to the travel lanes, they increase the likelihood for a crash to occur or to increase the crash severity.
The American Association of State Highway and Transportation Officials (AASHTO) Roadside Design Guide (RDG) suggests some safety treatments to reduce hazards from these structures (i.e., redesign using a traversable design, extend the structure outside the clear zone, shield the cross drainage structure).
Throughout this study, and after a thorough review of current state design practices, the researchers extracted culvert-related information from various resources provided by the Iowa Department of Transportation (DOT), such as their crash, geographic information management system (GIMS), and culvert databases, to determine the risk of crashes involving roadside culverts. Based on the results of these analyses, a related objective was to evaluate the cost-effectiveness of these safety treatments.
The study also involved a survey of state DOTs, highlighting current practices adopted by other transportation agencies throughout the US regarding the protection of culverts.