Colchester Exit 16 DDI project scheduled for 2020

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Colchester Exit 16 DDI project scheduled for 2020

Tue, 04/09/2019 - 3:38pm -- tim
The I-89 Exit 16 DDI (Diverging Diamond Interchange, looking north) project website is now live

Vermont Business Magazine The Vermont Agency of Transportation (VTrans) is improving the roadway along the US Routes 2/7 corridor, in the vicinity of I-89 Exit 16, to enhance mobility and safety in Colchester (Water Tower Hill/Costco exit). The project area extends from in the Colchester-Winooski town line north for approximately 1 mile to just beyond the intersection of Sunderland Woods Road at US Route 2/7. The core of the project is to reconfigure the existing tight diamond interchange to a Diverging Diamond Interchange at I-89 Exit 16. In part, drivers are diverted to the left side of the road.

The project is estimated to cost approximately $10 million and is scheduled to be advertised for contractor bid in fall of 2019 with contract award in winter of 2020. Construction is anticipated to begin in Spring 2020 and be completed over the course of two full construction seasons, ending in Spring 2022.

Meanwhile. RL Vallee, owner of nearby Maplefield's gas station on Route 7, has appealed the project to the Vermont Supreme Court, which heard the case on April 17. Vallee is claiming the project is in violation of Act 250 on environmental grounds. But the state has countered that the project is not in violation and, in any case, Vallee has no standing as an intervenor in the case.

Maplefields stands at the corner of the access road that leads to Costco. Costco wants to put in a gasoline station and has already installed the pumps. Vallee has long fought the Costco gas station on several environmental issues. Costco cannot proceed to actually pump gas until the Exit 16 interchange has been upgraded.

The first year of construction will consist mainly of utility relocation, ledge removal, and drainage work with the bulk of the roadway construction including the installation of the DDI, the addition of the turning lanes, and the implementation of the pedestrian and bicycle accommodations taking place the following construction season.

Other improvements include:

  • Adding turn lanes at the Mountain View Drive, Hercules Drive and Rathe Road intersections.
  • Construction of dedicated pedestrian and shared pedestrian/bicycle facilities.
  • Modernizing traffic signals at South Park Drive, I-89 Exit 16, Mountain View Drive, Hercules Drive, Rathe Road and at Tigan Street in Winooski City.
What is a DDI?

A Diverging Diamond Interchange (DDI) is an innovative, modern interchange design that can relieve traffic congestion and improve safety for drivers, bicyclists and pedestrians. In a DDI, traffic crosses to the left side of the roadway allowing for ease of access to the interstate by eliminating difficult left turns. With traffic diverted to the left side of the roadway, vehicles making a left onto the interstate entrance ramps do not have to cross oncoming traffic, creating fewer conflict points. The reduction of conflict points eliminates potential user collisions, thus improves safety and vehicle throughput. With left turn movements operating freely within the DDI, the traffic signals no longer require protected left turn phasing, improving overall traffic operations at the interchange. 

With left turn movements operating freely with the DDI, the traffic signals no longer require dedicated left turn phasing, improving overall traffic operations at the interchange. VTrans renderings.


What are the benefits of the Exit 16 DDI Project? 

The Exit 16 DDI Project will improve roadway conditions along US Routes 2/7 for safety and mobility. The DDI is anticipated to reduce traffic congestion and the number and severity of crashes occurring at the interchange of US Routes 2/7 and I-89. The addition of turning lanes and upgrades to the existing signals at adjacent intersections and improvements to pedestrian and bicycle facilities throughout the project area will also help mitigate congestion and safety concerns throughout the corridor. In addition, the DDI design allows for incorporation of the existing Interstate 89 bridges, therefore reducing the project footprint and impacts to adjacent properties. Using the existing infrastructure also dramatically decreases construction costs. Also, the DDI’s channelizing raised islands significantly reduces the number of wrong-way entrances onto the interstate.

Will the DDI cause driver confusion? 

No. Roadway elements such as signing, pavement markings and barriers will assist and guide motorists through the interchange properly.

How long will construction take? 

Construction is scheduled to begin in the Spring of 2020. The project will be completed over the course of two construction seasons and is scheduled to be completed in the Spring of 2022.

How can I learn more about the project?

The Colchester Exit 16 DDI website has an overview of the project and is a one-stop resource for all project related materials. Please visit the Document Library to preview all public outreach and meeting materials. Prior to construction, public meetings will be held to share project information and provide an opportunity for community discussion. Information on the Exit 16 DDI Project will also be available on VTrans social media accounts including Twitter, Facebook, Instagram, and YouTube. In addition, project news and construction updates will be emailed to those who sign-up for our email distribution list. Please submit your email to be added to the distribution list here.

If you have questions or comments about the Exit 16 DDI Project, submit a comment via the Comment Form or email VTrans at

Source: VTrans. 4.9.2019