The Vermont Agency of Transportation (VTrans) is about to begin construction on a highway interchange project unlike any other in the state, the department announced recently.
A diverging diamond interchange, or DDI, will be built starting Jan. 23 at Interstate 89's Exit 16 in Winooski, north of Burlington. The DDI will carry traffic from U.S. Highway 2/U.S. 7 under the freeway in a manner that has proven to be safer, increases vehicular capacity, and allows construction without impairment to the existing interstate.
First planned in 2012, the new type of highway junction was finally approved by the state seven years later. The design has become increasingly popular in other parts of the United States, but the Winooski DDI will be Vermont's first.
A video on the VTrans project webpage explains how the traffic flow will work with the new Diverging Diamond Interchange.
"The DDI is an innovative traffic configuration where vehicular traffic crosses to the left side of [the U.S. 2/U.S. 7] roadway between the two signalized intersections," according to the video. "This eliminates difficult left hand turns without increasing the number of lanes or traffic signals."
VTrans Shows What a DDI Can Do
In addition, the agency held a public meeting on Jan. 12 to give an update on the $14 million project's timeline and what drivers can expect when traveling through the exchange.
Michael LaCroix, the project manager of VTrans, noted that making the public aware of the DDI project is important because groundbreaking for the first phase will be at the end of January. He also said that the project footprint expands beyond the highway off-ramps and interchange area, WAMC Northeast Public Radio in Albany, N.Y., reported.
"The scope of the project is reconstruction of [U.S. 2/U.S. 7], otherwise known as Roosevelt Highway, in the town of Colchester, and it begins at the Winooski town line," he explained. "[From there], it goes 1.05 mi. up north toward Colchester Village and includes not just the roadway corridor but … improvements at signalized intersections as well."
The largest part of the Winooski DDI project is reconfiguring the highway exchange to the new interchange designs.
For the brief time drivers will cross over to the left side of the road on the DDI, LaCroix pledges that the new lane markings will be clear to them even in winter.
"It's only 400-ft.-long, at most, and almost all of it is underneath the interstate bridges," he explained. "I can understand people's discomfort of being on the left side of the road and not having any sort of direction. We're going to have very robust pavement markings so that they'll be more durable during the winter when the plows come through."
Blasting on Project No Cause for Concern
The contractor for Vermont's first DDI is Williston-based S.D. Ireland Construction.
Kurt Hutchins, the assistant project manager of S.D. Ireland, outlined to WAMC where and when blasting is planned, what to expect, and the precautions being taken. He said the blasting is the biggest public concern his company is hearing about regarding the project.
"People see movies and they think there are going to be fireballs and rocks flying everywhere," Hutchins added. "That is not going to be the case; it is going to be controlled."
He said people can expect a small series of explosions and a short delay between each one that will cause less ground vibration. As the charges will be placed underground, Hutchins explained, blasting mats will be stretched over the top of the trenches to keep debris from flying out.
"It will feel like an 18-wheeler drove by," he assured. "The blasting will not be loud, just a small rumbling and that's about it."
One resident at the meeting, though, expressed doubts about the DDI design.
"I've been in a variety of states where they have these [DDIs], and they are good for some areas, but I don't necessarily find that it would be good for up here. It's just going to make for mass confusion, especially with people that don't know how to manipulate in the multiple traffic patterns."
It must be noted, though, that these same objections have been voiced in other places across the country, but once those DDIs were in place, motorists quickly adapted to the road pattern and realized their benefits.
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