‘Temporary’ Green Line Slow Zone Approaches 1-Year Anniversary

An arch of the newly refurbished Lechmere Viaduct, pictured from Charles River Dam Road.
While the Green Line extension was being built, the MBTA also rehabilitated the Lechmere Viaduct over the Charles River to reinforce the century-old concrete spans with carbon fiber and replace the track infrastructure on top of the viaduct. The viaduct re-opened to transit service along with the rest of the new Green Line branch to Union Square on Monday, March 21, 2022.

A stubbornly persistent slow zone on the Green Line’s Lechmere Viaduct, the arched bridge over the Charles River, offers a case study in the MBTA’s struggles to retain credibility with riders who endure disruptive construction projects but have yet to see any tangible benefits.

Since 2020, the T has enacted two extended closures of the northern portion of the Green Line to facilitate major work on the Lechmere Viaduct (sometimes referred to as the East Cambridge Viaduct), the bridge that carries Green Line passengers between Lechmere Station in East Cambridge across the Charles River to Science Park/West End in downtown Boston.  

But in spite of all the work that’s been done, a “temporary” slow zone that has forced trains to run at a walking-pace crawl is now approaching its one-year anniversary. 

As part of the Green Line Transformation program, the T first shut down the viaduct in early 2020 for a thorough renovation of the structure.

The $87.4 million project involved a range of work, including the renewal of 3,500 feet of tracks, 70,000 feet of new signals, and reinforcement of the viaduct’s 12 concrete arches with carbon-fiber wrap for structural support, according to the project website

During the rehabilitation project, workers also replaced the overhead catenary system – the wires that supply electrical power to trains.

The project, originally set to span 18 months, reached substantial completion in March 2022.

The viaduct upgrades were done in tandem with Lechmere Station’s closure, relocation and reconstruction as part of the Green Line Extension project, whose first branch, to Union Square, also opened in March 2022. 

“With these improvements, Green Line riders can look forward to an increase in capacity and the expansion of dependable service into Cambridge,” said MBTA Chief of Capital Transformation Angel Peña in an MBTA announcement celebrating the project’s work. 

But almost immediately, riders noticed that trains were crawling across the newly-refurbished viaduct at unusually slow speeds.

In August, the T announced a month-long closure of the northern section of the Green Line, including the viaduct, in conjunction with its closure of the entire Orange Line. 

In a statement about that closure, the MBTA acknowledged that there had been problems with the newly-installed overhead wire on the Lechmere viaduct that had forced trains to run slowly.

When the line re-opened in mid-September, the T claimed that it had finished making “adjustments to the overhead wire on the East Cambridge Viaduct that eliminated a temporary slow zone, allowing trolleys to operate at the system’s designed speed of 25 mph on a permanent basis.“

“Green Line riders should note that slow zones will continue to be in place temporarily for about one week where the work was performed,” read the T’s statement. 

But according to data from TransitMatters, there has been no improvement to average train speeds across the viaduct since then, even after the T opened five new stations extending Green Line service from Lechmere to Medford in December.

According to TransitMatters’ data, the median travel time for trains running from Lechmere to Government Center – an approximate 1.5-mile stretch serving five stations – was 9.4 minutes on Wednesday, January 11. 

Trips in the opposite direction from Lechmere north to Ball Square – a longer 2.7-mile trip with the same number of station stops – took a median travel time of 8.4 minutes.  

“The MBTA continues working diligently to execute safe and rapid strategies to eliminate slow zones across the system. The slow zone is in place at the East Cambridge Viaduct as the MBTA awaits custom ties for the 110-year-old bascule span of the viaduct,” Lisa Battison, MBTA spokesperson told StreetsblogMASS over email last week. 

No date was given, but Battison said the ties will be replaced as soon as they become available.

“While these custom ties are being replaced, the MBTA will use this opportunity to access and replace rail. Based on projections related to working and weather conditions on the open deck structure over the Charles River and the availability of resources and materials, the work to remove the slow zone is scheduled to be completed in the spring of 2023,” said Battison. 

This rail replacement will be in addition to the track that was allegedly renewed during the Lechmere Viaduct Rehabilitation project.

Even the 25 mph speed target – still unmet – may be the product of reduced expectations.

In the T’s design-build contract for the Green Line Extension, released in 2017, the agency called for contractors to design for maximum inbound and outbound speeds of 50 mph between Science Park and the Red Bridge Interlocking, the complex of bridges located just north of Lechmere Station where the D and E Green Line branches split to Somerville and Medford, respectively. 

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