The Winooski circle can best be described as a traffic circle, an oval or a traffic circulator (Daryl Benoit's description--he is former CCRPC staffer). What Winooski's facility is not--it is not a modern roundabout.
Best example, take three of the 120-foot diameter Shelburne Street roundabouts (as designed for construction in 2017), or three of the Montpelier downtown Keck Circles, or three of the Middlebury roundabouts—three of these fit inside the Winooski facility with plenty of room to spare. Or, drop six of the 90-foot diameter full-service Manchester Center Grand Union roundabouts, still room to spare inside the Winooski circulator. Take two of the two-lane 172-foot diameter Brattleboro Keene Turn roundabouts and they fit easily inside the Winooski facility.
Big diameters means high speed, means higher crash rates. Solution to Winooski--tear out the middle area and put too normal sized two-lane roundabouts and provide lots of resulting unused space to the businesses which front the north/west/east sides of the street. This means, for example, no more going through the sidewalk "squeeze" at Sneakers, safe walk mode crossings all round, and much slower speeds. Besides the inside area gets no use at all now.
Current roundabout practice for urban areas with walk and bike mode use are 90-130 feet diameter for a single laner and 150-180 feet diameter for a two laner. All 10 Vermont busy street roundabouts (plus two under construction) conform to these diameter ranges.
Roundabouts are all about safety and cut overall serious injury and fatality rates by about 90%. Ditto for single lane roundabouts for walk mode. Seniors are particularly vulnerable at intersections when walking or driving. While a quarter of all fatalities in the U.S. occur at intersections, more than half all senior driver fatalities occur at signed or signaled intersections. Except for depth perception senior drivers ability equals that of younger drivers. Not a single walk fatality has yet occurred at the more than 4,000 U.S. roundabouts since the first roundabout was built in 1990 in Las Vegas. No wonder AARP advocates replacing existing traffic circles with roundabouts. But here in Burlington our walker fatality rate at our 75 signalized intersections is about one per decade plus lots of serious injuries during recent years.
The Burlington Walk Bike Council seeks a demonstration roundabout next summer at an all-way stop intersection so all our residents can have some first hand experience with a roundabout without having to go to Middlebury, Manchester or Montpelier downtowns. Also on VT 15 there are roundabouts in Cambridge, Hyde Park and a new one under construction in Morrisville (Waterbury US 2/VT 100 on Main Street also under construction).
Finally, for New York State Department of Transportation “roundabouts first” policy dates from 2005 and now is the approach of other state departments in Virginia, Rhode Island, Florida and Maryland. Vermont was the first to have a state law requiring consideration of a roundabout at any dangerous intersection because of the safety improvement offered by the roundabout. It’s the law!