As a northern entrée to Waterbury, the newly constructed traffic roundabout joining Routes 2 and 100 opened to traffic earlier this week.
Engineers say the roundabout will improve traffic flow as well as safety at the busy intersection, which once handled a peak of 12,000 mostly rush-hour vehicles per day.
The modern traffic roundabout, popularized by the British, is found throughout the world in countries from Australia to the United Arab Emirates, with 30,000 arterial connectors in France alone.
However, traffic roundabouts — or rotaries — have been slow to win acceptance from some Vermont drivers, accustomed to the stop-and-go flow of the traffic light.
Engineer Carl Richardson of the South Burlington-based design firm Stantec says the roundabout will improve safety for drivers and pedestrians, while reducing queues that once stretched as long as 600 feet.
“With the roundabout, you have a more free flow of traffic and you don’t have the yellow or red signals at the intersection that cause delay,” Richardson told Waterbury residents earlier this year at a public hearing. “You have yield conditions versus stop conditions that have been proven to provide more capacity to motorists.”
Officials chose to redesign the Waterbury intersection after the Vermont Agency of Transportation in 2007 conducted a traffic scoping study to analyze the flow of cars, trucks and pedestrians at the intersection.
Officials considered a couple of options before choosing the roundabout, including the installation of additional traffic signals. They also considered making no changes at all, and simply accepting longer waiting times as hundreds of state workers return next year to downtown offices destroyed in 2011 by Hurricane Irene.
Yet the roundabout offers a few primary safety upgrades, engineers say. The large circular design compels drivers to slow upon entering the intersection, with traffic flowing in one direction rather than three — features that allow improved visual contact with pedestrians. As an ancillary benefit, motorists may make U-turns without incurring a high risk of collision; all they need to do is go around the circle.
Studies conducted by the U.S. Federal Highway Administration have shown the design reduces overall crashes at an intersection by 37 percent, with a 90 percent reduction in crash-related deaths.
Some Vermonters may also appreciate an expected reduction in air pollution, as drivers spend fewer minutes per day idling at the intersection.
With the roundabout largely done — just finish work and landscaping remain — the construction focus will shift a couple of hundred yards north to Interstate 89 on- and off-ramps at Exit 10.
This fall, crews are doing preparatory work for a project next year that will replace the decking on both northbound and southbound lanes of the interstate, and completely replace a bridge over Stowe Street that’s part of the northbound exit ramp.
In addition, planning continues for an overhaul of a mile-long stretch of Main Street, from a point near Route 2 through downtown to the bridge over the Winooski River.
Main Street will be completely rebuilt, sewer and water lines replaced, utility lines buried, and sidewalks brought up to modern standards.
The starting date for that job has not been firmed up; it depends in large part on how long it takes state officials to negotiate easements and rights of way along Main Street.