Best Practices for Road Weather Management Version 2.0
Title:
Synthesis of the Effects of Wet Conditions on Highway Speed and Capacity
Abstract:
Wet and rainy conditions impact the driver, vehicle, and roadway. These effects cause a reduction in speed or density (car-following headway) or both which, in turn, cause a reduction in highway capacity. This paper is a synthesis of 26 studies relating wet conditions to speed and capacity. If the results from all reviewed studies after 1980 with original data from freeways are averaged assuming equal weights, then, the average speed reduction is 4.7 mph in light rain (HCM2000 suggests 6.0 mph which is similar to FHWA's 10 percent reduction) and 19.6 mph in heavy rain (HCM2000 suggests 12.0 mph which is higher than FHWA's 16 percent reduction.) The average capacity reduction is 8.4 percent in light rain and 20.0 percent in heavy rain. The impact of rainy conditions on highway capacity is important. Much additional research is needed for reducing the wide variance of observations in past studies. A methodology is needed for capacity and LOS analysis of freeways, intersections and arterials that accounts for wet conditions as part of typical conditions.
Source(s):
University of Hawaii-Manoa, Department of Civil Engineering
http://www.eng.hawaii.edu/~panos/wet_synthesis.pdf
Date: 2003
Author:
Prevedouros, Kongsil
Keywords:
Capacity
Rain
Pavement condition
Precipitation
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