The Chittenden County Regional Planning Commission is working with VTrans to look into what the Interstate 89 corridor should look like several decades from now.

The two organizations are calling their effort the I-89 2050 Study. Some of the people behind the study briefed a wide range of South Burlington city officials on it Wednesday night.

The decades-old proposal of building Exit 12B on Hinesburg Road in South Burlington is one of five options on the table in the study. The other four involve various re-configurations of Exit 13 or Exit 14.

“After we narrow down which interchanges to look at, we’re really going to be looking at comprehensive bundles (of improvements), and I think if you think about Bundle 1, kind of do everything we can to not have to spend tens of millions of dollars,” Chittenden County Regional Planning Commission executive director Charlie Baker said.

The five options will be evaluated through metrics like efficiency of movement, community livability and traffic safety. The traffic safety piece of a possible Exit 12B — which showed a projection of fewer crashes on the highway corridor if the exit is built — caught the attention of Donna Leban of the South Burlington Bicycle & Pedestrian Committee.

“With adding an interchange, I’m not quite sure how you assume that it’s going to have fewer crashes,” she said. “Because you’re adding a whole bunch of extra traffic there, and you’re adding a lot of speed that isn’t there now.”

VHB, a Massachusetts-based engineering firm, has a South Burlington office.
The director of that office said that even with more crashes on, and near, Hinesburg Road, Exit 12B would reduce crashes by a large enough amount in other areas to lead to a net reduction overall.

“If you add 12B, what we do know is that it draws traffic off of Williston Road and some traffic out of Exit 12 — increasing the crash expectancy around the interchange but reducing it elsewhere, and so the net/net is what’s shown here,” VHB South Burlington managing director David Saladino said.

The latest construction estimate for Exit 12B is $29 million. As steep as that sounds, it’s actually come down significantly in the last two years — it was $42.4 million when the study began.

Saladino also argued that some of Exit 12B’s construction cost would be recouped on maintenance. The existing highway overpass would be replaced with a new bridge, and upkeep is a great deal more expensive for a bridge 60 years old or more than it would be for a new bridge.

“The interstate was built in the early ’60s,” he said. “All of these bridges were also built at that same time, the ’60s. We assume about a 75-year lifespan for bridges. We’re getting close to the end, the end time, for most of the bridges through this section.”

Wednesday night’s session was open to the public, but there will be a public forum in South Burlington a week from tomorrow — Thursday, March 18th. You can find a link to the Zoom meeting here, as well as comprehensive information about how the I-89 2050 Study is progressing so far.