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Best Practices for Road Weather Management Version 2.0

Best Practices > Publications > Publication Titles

Title:

An Investigation into the Impact of Rainfall on Freeway Traffic Flow

Abstract:

The purpose of this research effort was to investigate the impact of rainfall, at varying levels of intensity, on freeway capacity and operating speeds. Findings were derived from traffic and weather data collected in the Hampton Roads region of Virginia. Light rain (0.01 to 0.25 inches per hour) decreases freeway capacity by 4 to 10 percent. Heavy rain (0.25 inches per hour or greater) decreases freeway capacity by 25 to 30 percent. The presence of rain, regardless of intensity, results in approximately a 3 to 5 percent average decrease in operating speed. The findings indicated that the impact of rain is more significant than currently reported in the Highway Capacity Manual.

Source(s):

83rd Transportation Research Board (TRB) Annual Meeting; University of Virginia, Department of Civil Engineering. For an electronic copy of this resource, please direct your request to WeatherFeedback@dot.gov.

Date: 2004

Author:

Smith, Byrne, Cooperman, Hennessy, Goodall

Keywords:


Mobility
Rain
Traffic management
Precipitation

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