October 15th, 2013

Whatever the Weather

Optimize Mobility, by Catherine Higgins.

During storms, driving conditions can cause travel delay, especially during the morning and evening commute.

When a storm hits the Wasatch Front, a twenty-minute commute can turn into an hour due to slick roads, start-and-stop traffic and low visibility. What if traffic could be managed more effectively to minimize the sluggish traffic speeds drivers experience during storms?

Recent technological advances in assessing weather and controlling signals have given traffic engineers better tools to keep traffic moving in stormy weather. On some corridors along the Wasatch Front, UDOT is taking a Weather Responsive Traffic Management approach that puts the tools to use.

WRTM uses sensors, traffic signal plans designed for storm conditions, and sophisticated traffic monitoring systems already in place to move traffic more efficiently during winter weather.

Traffic on Riverdale Road PhotoDuring winter months in 2013, an urban arterial in northern Utah served as testing area for WRTM. Riverdale Road intersects a busy shopping district and connects four Utah cities with Interstates 15 and 84. Over 47 thousand vehicles travel the corridor each day.

UDOT’s results in managing Riverdale Road traffic during winter storms were very good – for motorists, that is. Drivers experienced less stopped time at intersections compared to other storm days, and overall, traffic speeds were not significantly impacted by weather.

Here’s how the WRTM system worked on Riverdale Road:

  • Traffic engineers created signal timing plans for implementation before or during a storm. The plans accommodate travel speeds that are likely during storms so that signalized intersections along the corridor work together to make traffic flow more efficient.
  • A Road Weather Information System unit was installed in the corridor. The RWIS helped meteorologists and engineers anticipate upcoming storm severity to decide which signal timing plan to employ.

    RWIS on Riverdale Road Photo

    RWIS on Riverdale Road

  • Detection units were installed overhead along the roadway. The new equipment is better at detecting traffic movement during storms, and the equipment gave UDOT traffic speeds.
  • To monitor traffic during storms, UDOT used a Signal Performance Metrics System that lets signal operators assess and adjust traffic in real-time. After a storm, the system can be used to evaluate how the signal plans worked.

Winter 2013 ended up being a challenging year to test the WRTM system. During testing, the Salt Lake City and Ogden area experienced one of the worst winter storms in the past decade. Nevertheless, post-storm review showed an average or above average improvement in performance in traffic operations in over half of the weather events, including during the major storm.

Post-storm analysis also shows that cars maintained a high level of progression from intersection to intersection with platoons of cars arriving on green lights. When platoons of cars arrive at intersections on green lights, traffic flow throughout the corridor is more efficient.

Based on the success of the Riverdale Road WRTM performance, UDOT plans to expand the system to other corridors.

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