Abstract
ObjectiveSingle vehicle run-off crashes in urban areas constitute a growing problem that deserves more attention from authorities and researchers. This study aims to detect geometric road design risk factors characterizing places where urban run-off crashes might happen.MethodsA case-control study was performed in the urban area of Valladolid (Spain) with data corresponding to a four-year period. Logistic regression models were used to analyze data, considering different variables related to design parameters in the models: type of intersection, radius of curvature, width of the pavement, width of the traffic lane, number of lanes for traffic in the same direction, direction of the traffic, length of the previous straight section, distance to the previous traffic light, slope, and finally, priority regulation. Two different scenarios were investigated: intersections and curves.ResultsThe Adjusted Odds-Ratio of a run-off crash was five times higher in double direction roads with median strip than in one-way urban roads, for both curves and intersections, and almost nine times higher on road sections with previous straight lengths greater than 500 meters. Specific risk factors for intersections are “number of lanes for traffic in the same direction” (the odds of a run-off crash are more than five times higher on a road with two or more lanes), “length of preceding straight section” (the odds on road sections with lengths greater than 500 meters are more than nine times that of road sections with a length of less than 150 meters). For curves, specific factors are “width of the traffic lane” (the odds of a run-off crash on curves with lanes wider than 3.75m are more than six times higher) and “priority regulation” (the odds of a run-off crash increases more than twelve times on road sections with traffic light regulation over those without any regulation).ConclusionsThe current study identifies urban road configurations that might require redesigning with the aim of decreasing the odds of a run-off crash, or the implementation of passive protective systems to mitigate their consequences. Specifically, intersections in two direction roads with median strip, more than two lanes per direction and a long preceding straight section, as well as curves with wide lanes and traffic light regulation, are the places that require attention.
Highlights
1.35 million people die yearly on the roads, traffic crashes are predictable and preventable [1]
Specific risk factors for intersections are “number of lanes for traffic in the same direction”, “length of preceding straight section”
Run-off crashes could be considered more prevalent on rural roads, run-off crashes in urban environments must be considered due to their high frequency (for instance, in South Australia [5] and New Zealand, run-off crashes amounted to 20% of urban injury crashes and 48% of urban fatal crashes; the second most frequent type of urban injury crash was run-off road collision (16%) [4])
Summary
1.35 million people die yearly on the roads, traffic crashes are predictable and preventable [1]. The increased incidence of urban run-off crashes could be related to the increased exposure to urban environments: more than 50% of the world population lives in urban areas and this share is expected to increase in the future (i.e., in Spain, up to 75% in 2050 [6]). Different studies [7,8,9,10,11] have analyzed road risk factors involved in run-off crashes on rural roads, while others provide descriptive [12] or inferential [13,14,15] studies of run-off crashes on urban roads; they [13,14,15] have sometimes focused only on very specific locations (urban arterial roadways or urban shopping road segments). General information about run-off crashes in rural and urban areas together is given [22,23]
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