Road Weather Management Program
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Best Practices for Road Weather Management Version 2.0

Title:

The Effect of Weather on Free Flow Speed

Abstract:

Free flow speed is affected by pavement conditions, visibility and wind speeds. The effects of poor weather should be considered in such cases as part of capacity and level-of-service analyses. The authors are primarily interested in determining the factors that affect free-flow speed on a basic freeway segment and, if possible, to quantify these relationships. To meet this objective, the following questions were considered. Are speed characteristics different in good weather and bad weather? What is the free flow speed for this site during good weather? At what point does reduced visibility affect free flow speed? Do high winds affect free flow speed, and, if so, at what level? What are the individual effects of pavement conditions, wind speed, and visibility when considered collectively? How do the effects of bad weather on speed measured in this study compare with previous studies? How often does bad weather occur?

Source(s):

80th Transportation Research Board (TRB) Annual Meeting; University of Idaho, Boise State University and Meyer Mohaddes Associates. For an electronic copy of this resource, please direct your request to WeatherFeedback@dot.gov.

Date: 2001

Author:

Kyte, Khatib, Shannon, Kitchener

Keywords:


Visibility
Wind
Adverse weather
Capacity
Mobility
Speed

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