BOSTON — An environmental group is taking the Baker administration to court over its decision to temporarily lift restrictions on the carpool lane along Interstate 93 to ease traffic congestion.

On Tuesday, the Conservation Law Foundation filed notice in U.S. District Court in Boston that it intends to sue the state Department of Transportation, alleging that the change violates the federal Clean Air Act and state environmental laws that designate lanes for carpoolers. The suit will ask a federal judge to return the lane to restricted use.

"The decision to close the HOV lane was made hastily and clearly violates state and federal laws," said Staci Rubin, a senior attorney at the foundation. "The HOV lane was created to improve air quality and to encourage the commonwealth to move more people in fewer vehicles."

Rubin said feedback from public transit and bus companies suggest that opening up the lane to general traffic has caused delays for commuters who use the HOV lane.

"This is benefiting single drivers from the North Shore while burdening people who live closer and use public transit," she said. "That's just blatantly unfair and contributing to our congestion and air quality and climate crisis."

The Tobin Bridge, a primary access point to Boston for those driving on Route 1, has seen heavier-than-usual traffic as crews work on a two-year renovation of the aging landmark. Commuters have been finding alternative routes in and out of the city, which has increased traffic on I-93 and other highways.

To help relieve the congestion, the Department of Transportation in May opened the high-occupancy lane between Medford and the Zakim Bridge in Boston to all motorists, regardless of how many people are riding in a vehicle. While the switch is meant to be temporary, MassDOT officials are considering keeping it open to traffic for the duration of the bridge project.

But the HOV lane closure has drawn criticism from environmental groups and transportation advocates who say the move is wrongheaded.

Chris Dempsey, director of the advocacy group Transportation for Massachusetts, said his group backs the legal challenge against MassDOT's decision to open up the carpooling lane, which he said "goes against its own stated goal of moving more people in fewer vehicles."

"Decisions like this one have left Greater Boston with the worst traffic congestion in the country," he said.

Transportation Secretary Stephanie Pollack declined to comment Tuesday on the pending litigation, saying she hadn't had a chance to review the complaint.

State lawmakers representing the North of Boston region, including Reps. Frank Moran, D-Lawrence, and Tram Nguyen, D-Andover, wrote to MassDOT in June expressing concerns about the changes to the lane, which were implemented without public hearings or input.

The 2.6-mile HOV lane north of the city is one of two sections of the highway designed to encourage carpooling during peak hours. The other is along a five-mile stretch of the Southeast Expressway between Furnace Brook Parkway in Quincy and Morrissey Boulevard in Boston.

North of the city, travel in the inbound HOV lane is usually restricted between 6 and 10 a.m., on weekdays. During those times, vehicles must have at least two occupants in order to use it.

On the Southeast Expressway, so-called "zipper lanes" change for the morning and afternoon commutes, allowing HOV travel northbound from 5 to 10 a.m., and southbound between 3 and 8 p.m. on weekdays.

The Tobin Bridge's two-year rehab will involve lane closures on the north and southbound sides of Route 1. Two of the three northbound and southbound travel lanes will be open during the day, and one of the three in each direction will be open overnight.

The MBTA is also encouraging people to use the commuter rail and offering free fares for inbound trips on the Silver Line 3, between Chelsea and South Station, as well as additional Blue Line capacity. Officials are also encouraging commuters to use the Haverhill or Newburyport/Rockport rail.

MassDOT said crews are using accelerated techniques to speed up the maintenance project, which is expected to wrap up by 2021.

Christian M. Wade covers the Massachusetts Statehouse for the Times and its sister newspapers and websites. Email him at

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