Road Weather Management Program
photos of lightning, trucks plowing snow, an empty road before a storm, and an evacuation
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Best Practices for Road Weather Management Version 2.0


Urban Freeway Crash Analysis: Geometric, Operational and Weather Effects on Crash Number and Severity


The associations between the number of crashes and the severity of crashes with a long list of potentially contributing factors such as geometric and operational characteristics as well as weather conditions were investigated using both aggregate and disaggregate databases with crash statistics. Severity was estimated using constants for the different impact (cost) of fatalities, injuries and material damages. Noteworthy associations include the negative correlation with the speed limit (lower speed limit spots have more or more severe crashes), existence of zebra markings (suggesting the possibility of an illegal driving maneuver), downhill grade sections, and curves. Several temporal variables such as months, days or time of day with a higher frequency of crashes worked well in models, but these are findings of local interest. An important outcome of this analysis is the absence of any major correlation which implies crashes on the modern and mildly congested Attica Tollway are events largely attributable to driver behaviors and other circumstances that cannot be accounted by geometric, operational and other temporal variables. The findings of this research suggest that fixed and temporal roadway characteristics and the presence of rain or wet pavements may explain (and likely contribute to) about 5% to 10% of the crashes and severity of crashes observed in 2004 and 2005 on Attica Tollway. The 2006 report from the 100-Car Naturalistic Driving Study concluded that nearly 80% of all crashes involved driver inattention which lends support to the finding that roadway and environmental factors are relatively minor causes of crashes.


86th Transportation Research Board (TRB) Annual Meeting; Attikes Diadromes SA (Greece) and University of Hawaii-Manoa. For an electronic copy of this resource, please direct your request to

Date: 2007


Kopelias, Papadimitriou, Papandreou, Prevedouros


Pavement conditions

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