Innovations in Impact-Based Wintertime Road Weather Warnings in Utah

Four interstates, multiple major US through routes, and a vast network of rural state highways cross Utah's complex terrain between 4,000 and 9,000 feet in elevation. These roads are responsible for transporting freight, cross-country travelers, weekend recreationalists and commuters. The Wasatch Front Metro area is a major urban center of the intermountain west, with a rapidly growing population currently estimated at around 2 million. Each year, winter storms account for multiple highway impacts, including closures, incidents and major congestion. Traffic incidents reported across the state can increase as much as 10 fold during snow and ice events.

It is no surprise then, that public usage of the Utah Department of Transportation's (UDOT's) traveler information outlets—both phone (511) and web—quadruples during snowy months, with spikes in usage clustered around storm days. The amount of weather-related public phone calls and emails to UDOT's Traffic Operation Center, as well as website usage, has continually increased over the past few years.

The increase in public interest in wintertime road specific forecasts and weather warnings has spurred a unique collaborative effort between federal (NWS), state (UDOT) and private (NorthWest Weathernet) entities. Multiple changes have resulted: communication between the three offices takes place on a daily basis; briefings before, during and after storm events ensure that the same public message is released from each entity; forecasters at UDOT's Traffic Operations Center developed and released an impact-based forecast within the last year; and the local NWS forecast office in Salt Lake City has relaxed its criteria for issuing watches and warnings to allow for impact-based criteria as much as, and sometimes more than, weather thresholds. Additionally, local media and UDOT public involvement personnel have taken an active role in the effort to relay a shared message.

Through this more synergistic effort, our aims are:

- To relay a greater sense of expected storm impact in NWS watches and warnings,

- To reduce public confusion by providing consistent wording from multiple forecasting entities,

- To maximize accuracy and reduce duplication of effort,

- To reach a wider audience, and, ultimately,

- To alter traveler behavior and, in so doing, reduce personal property damage, ease storm clean-up response and reduce congestion.

There are multiple efforts taking place designed to assess whether or not mitigation strategies have any influence on driver behavior during storm events. The UDOT Traffic Mobility Section monitors driver behavior utilizing a complex network of 240 Traffic Monitoring Stations along Utah's urban freeway system. UDOT's Weather Operations Section employs the use of 70 Road Weather Information Systems (RWIS), plow driver observations, road condition forecasts and Traffic Operations Center (TOC) Operator reports to monitor and track the impact of weather on area roadways and traffic patterns. Public surveys are being developed between the University of Utah and NWS SLC office. After action reviews are created using data and impact observations collected at the NWS SLC office and UDOT's TOC.

This presentation will introduce the concepts of two impact-based warning systems and overview the collaborative effort among forecasting entities within Utah. Two winter storm events (November 23rd and November 28th) will briefly be discussed, including assessments of storm impacts and public response after warnings were issued.