Evaluation of a Variable Speed Limit System for Wet and Extreme Weather Conditions

The objectives of this project are to develop and evaluate an advanced, weather-responsive, speed limit adjustment system for the Oregon Department of Transportation (ODOT).

Wet and icy road conditions reduce pavement friction, increasing the potential for crashes when vehicles are traveling too fast for the conditions. The Oregon Department of Transportation has documented a high rate of “loss of control” crashes on the ramps of the U.S. 26/Oregon 217 interchange in Beaverton attributable to wet conditions. While the site has traditional passive signage and flashing beacons in place, crashes continue to occur. Oregon Department of Transportation (ODOT) personnel have concluded that additional measures are necessary to address the problem. The goal of this study is to reduce the occurrence of wet weather crashes on the interchange ramps of the U.S. 26/Oregon 217 interchange in Beaverton, Oregon through the use of a weather-responsive variable speed limit system. Such a system will post appropriate speed limits based on weather conditions, with the intent of lowering motorists’ speeds accordingly. To this end, the overall objectives set for this research are to investigate the development and application of a speed limit adjustment system that incorporates weather conditions, evaluate its effectiveness once deployed and develop guidelines to direct future consideration and deployment of similar systems.