AASHTO Journal, 13 July 2012
Wyoming Department of Transportation tackled a congestion nightmare and a crash-plagued intersection when it rehabilitated the high-volume principal arterial Vandehei Avenue in Cheyenne.
The 50-year-old bridge over the highway had “surpassed its useful lifespan,” so WYDOT decided to look at the area and come up with a plan to make the area, which crossed I-25, safer and more practical.
WYDOT wanted to widen the roadway, which would cut back on the congestion that had become the norm for drivers during peak hours. Crashes were also all too common in the area, while pedestrian facilities were severely lacking at the interchange. In order to address these concerns and figure out how to best alleviate them, WYDOT used both current and 20-year projected traffic volumes for modeling. From that research, WYDOT decided single-lane roundabouts would be the best option to improve traffic flow at the interchange.
The $6.1 million project began in April 2011 under an accelerated construction schedule, with completion scheduled for the end of June 2011. WYDOT worked closely with contractors to keep the project on schedule, which ultimately led to an early completion date of May 25, 2011.
Since the new roundabouts were constructed a year ago, WYDOT has seen crashes drop a staggering 54.5 percent. While traffic engineers typically rely on three years of crash data (and not one), WYDOT is encouraged by the initial data.
Also encouraging is WYDOT’s success in cutting down on delays per vehicle at stops, which could reach up to 45 seconds.
“We had predicted an average delay of somewhere in the six to eight seconds per vehicle range for roundabouts, and we’re doing better than that,” said Paul Jones, WYDOT’s assistant state traffic engineer, in a statement. “So these things are operating quite well and quite safely. We’re not getting long queues of vehicles waiting to enter, and the queues dissipate quickly.”
Pedestrians also see the benefits. Crossing the intersection is safer with the roundabouts as they now only cross one lane of traffic at a time and have the option of waiting on splitter islands until they can cross the second lane.