Assessment of Weather-Related Congestion On Utah's Highways:Investigation of Event Impacts From the Winter of 2008-09'

Over the past several decades, Utah has experienced rapid population growth including a nearly 24% increase between 2000 and 2008 alone. This has resulted in increased demand on Utah's existing interstate and arterial infrastructure. Recurring traffic congestion (i.e., AM/PM peak commute times) and non-recurring congestion (i.e., weather-related) result in an average annual cost of $250 million dollars in Utah alone. Recent Utah Dept of Transportation (UDOT) studies have confirmed that inclement weather plays a significant role in non-recurring congestion and associated negative impacts with respect to delays, mobility, productivity, and safety. It is important to note that one of the most cost effective solutions for mitigation of the congestion problem is driver habit modification.

In an effort to measure and potentially mitigate weather-related traffic congestion, a cooperative effort between federal (National Weather Service Salt Lake City), state (UDOT), and private sector (NorthWest Weathernet) entities is being undertaken. The intent of the project is to develop mitigation strategies for non-recurring congestion associated with inclement weather. It is hoped that mitigation strategies can be developed that will influence driver behavior and, ultimately, reduce delays and congestion while at the same time minimizing accidents and the loss of productivity. To assist in this endeavor the UDOT Traffic Mobility Section will monitor driver behavior utilizing a complex network of 240 Traffic Monitoring Stations (TMS) along Utah's urban freeway system. Performance measures will be developed to assess the impact of weather on traffic patterns as well as whether or not mitigation strategies have any influence on driver behavior during storm events. UDOT's Weather Operations Section will employ the use of 61 Road Weather Information Systems (RWIS) as well as, plow driver observations, road condition forecasts, and Traffic Operations Center (TOC) Operator reports to monitor and track the impact of weather on area roadways.

This presentation will compare and contrast numerous weather events which impacted commuters in the Salt Lake City area during the winter of 2008-09'. Measures such as average travel time between TMS, average speed, and vehicle spacing will be assessed. In addition, the use of enhanced societal impact wording in National Weather Service statements, as well as UDOT 511, CommuterLink web reports, and targeted news releases and their possible influence on driver behavior will be discussed. Finally, advisory and warning lead times will be investigated with respect to their potential influence on event impacts.