State transportation planners are drafting proposals to reduce congestion and improve safety at the interchanges where Interstate 495 meets the Massachusetts Turnpike and Route 9, improvements that local officials say are needed to accommodate future growth along the I-495 corridor.
Planners are also exploring ways to reduce congestion on a nearby stretch of Route 9 in Westborough and Southborough.
The interchange proposals are largely designed to lessen the interweaving of traffic streams as they move from one highway to another, said Calli Cenizal, project manager for the study.
“You’re driving really fast up 495, the cars coming off Route 9 are going more slowly, and you have this weave pattern,” Cenizal said. “It causes crashes. It’s a huge safety issue. There’s a short amount of distance. There’s not a lot of time to act and react to what’s going on.”
The same issues are at play at the interchange of I-495 and the Mass. Pike (Interstate 90), Cenizal said. Vehicles changing from one highway to another have to weave through other traffic as they approach and depart from the toll plaza.
The I-495 interchange with I-90 was the site of 208 crashes from 2007 to 2009, the most recent years the state made available; the interchange with Route 9 saw 106 crashes during the same period.
The state Department of Transportation presented its preliminary recommendations for addressing the issues last month, and a draft report is expected to be completed next month. (Once it is released, the state’s draft report will be available online at www.massdot.state.ma.us/planning.)
Funding, however, has not been lined up for the improvements, which the state estimates would cost in the neighborhood of $130 million to $140 million altogether.
Officials in the towns that surround the interchanges — Hopkinton, Southborough, and Westborough — expressed support for the recommendations.
“Obviously, we’re in favor of improving the traffic flow through there and the safety,” said Elaine Lazarus, Hopkinton’s director of land use, planning, and permitting. “Those do need to be addressed.”
“If you drive up and down 128, you can see interchange after interchange, bridge after bridge, massive amounts of money being spent,” said Eric Denoncourt, Southborough’s town planner. Interstate 495, he said, “is sort of the forgotten highway.”
At the interchange of I-495 with Route 9, state planners recommend “braided” ramps for traffic exiting I-495. Such ramps would allow vehicles to bypass oncoming traffic, rather than weave through it.
At the interchange of I-495 and I-90, planners recommend a more complex series of fixes. In the short term, additional signs would be posted to help corral drivers into the correct toll lanes as early as possible, and a curve in the ramp onto I-495 northbound would be flattened out to make it safer, particularly for large trucks.
Eventually, a direct ramp from I-495 north to I-90 east would be added, the I-495 south offramp would be expanded, and the I-495 south onramp would be widened, among other changes.
If the proposals are implemented, exiting vehicles would no longer be required to weave in and out of other traffic.
Paul Matthews, executive director of the 495/Metrowest Partnership, called the interchange a major gateway for the entire region. “It’s backed up all the time, both on the Pike and 495,” he said. “For years we’ve heard that interchange is a major choke point.”
As for Route 9, planners recommend widening it between Computer Drive, just west of the I-495 interchange in Westborough, to Deerfoot Road in Southborough, and improving several intersections along the roughly 2-mile stretch.
“There’s a need for capacity in the highway system,” said Denoncourt, noting that Route 9 “becomes a parking lot at certain times of the day.”
On Interstate 495, the number of cars actually went down between 2004 and 2011, but the corridor is the site of substantial planned development, and planners expect large traffic spikes over the next two decades.
State projections show peak-hour traffic increasing by 15 to 20 percent or more by 2035, which would mean an extra 2,000 cars per hour on some stretches during certain hours.
“It’ll be a lot more cost-effective to build the infrastructure now, before the growth comes,” Denoncourt said.
Jim Robbins, Westborough’s town planner, said officials in his community are in favor of the proposed changes, but he said the key will be finding the money to implement them.
“The report is nice. Everybody is in favor of speeding traffic through the interchanges,” he said. “But if there’s no money to carry out the recommendations, then it’s just another study that sits on the shelf.”
Such a large project would likely require a mix of federal and state funds, and some components — such as the Route 9 improvements — could be paid for by the local communities and developers. In order to be eligible for federal funding, the interchanges need to be identified as top priorities by regional planners, and placed on long-range transportation plans.
“On the plus side, we’re not talking a Band-Aid,” said Matthews, the 495/MetroWest Partnership director. “That being said, any time a project is that expensive, it makes it harder to fund.”
Matthews said the political process around funding could prove tricky because I-495 separates Southborough and Westborough, and each community is in a different metropolitan planning organization. The regional bodies make decisions on how to spend transit dollars, and Matthews said the state should take a leadership role in coordinating them.
Denoncourt, the Southborough planner, said he doesn’t think I-495 is always given its due when it comes to transportation funding. “They do a lot of these studies, but there’s not a lot of money spent on 495,” he said. “I think it’s unfortunate.”
Cenizal, the project manager, said the recommendations could potentially be implemented piecemeal so that not all of the funding would be needed at once.
“These improvements can be made independent of each other,” Cenizal said. “You don’t necessarily need all of the changes to take place to see a benefit.”Calvin Hennick can be reached at firstname.lastname@example.org.