It happened fast.

The Maryland Transit Administration announced Thursday that it was shutting down the Baltimore area’s light rail line indefinitely out of concern for rider safety.

The move, which took effect Friday, has left thousands of daily riders without daily service, instead relying on shuttle buses to ferry them between light rail stops.

MTA Administrator Holly Arnold cited two separate mechanical issues discovered in vehicle inspections as the cause for the shutdown. Baltimore’s aging light railcars are in the process of critical rehabilitation work that is also long overdue, leaving some transit advocates wondering how the state let the situation get to where it is.

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So what’s wrong, why, and how did we get here? Here’s what you need to know:

What mechanical issues caused the shutdown?

A recent maintenance inspection following an Oct. 21 fire event revealed punctures in high-voltage conduits that connect rail cars to their power source, Arnold said at an emergency news conference Thursday. Vehicle overhaul contractor Alstom assisted the agency in conducting a risk assessment, and initially determined the issue did not require a full suspension of service. One person suffered minor injuries during the Oct. 21 fire, Arnold said.

Inspectors found a second mechanical issue with the cables that connect rail cars to one another, which Arnold said caused multiple smoke events over the past two years. A risk assessment for this issue similarly did not necessitate full suspension of service on its own.

Arnold and her team decided to pull the entire fleet from service “out of an abundance of caution” to inspect each rail car for the same problems.

How long will the light rail be out of service?

It’s unclear. Arnold said that her team and engineers from their rehabilitation contractor are working quickly to determine how many vehicles have the mechanical issues. She said that as soon as they have eight rail cars ready for action, limited service will resume, and that full service will be reinstated once they have 19 rail cars.

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On Friday, she tweeted out a photo of rail cars being repaired and wrote: “The @mtamaryland and Alstom teams have been working nonstop on vehicle inspections and are beginning repairs. We’ll be sharing our progress regularly as we work to restore service.”

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Will this affect other modes of public transit?

Shuttle buses will stop at light rail stations and offer service to riders while the rail cars are fixed up. Arnold acknowledged that this could affect service levels on Baltimore’s LocalLink and CityLink bus lines as 30 vehicles were being pulled from their normal routes to provide the shuttle service. This could mean slower bus service for students who rely on the MTA to get them to school.

The suspension of light rail service does not affect Baltimore’s Metro SubwayLink, a heavy rail line, or the three lines of MARC commuter train service, which includes service to Washington, D.C.

How many light rail cars does Baltimore have and how old are they?

The MTA light rail fleet consists of 53 rail cars, which Arnold said range in age from 24 to 31 years old. Light rail service debuted in 1992 in conjunction with the opening of Oriole Park at Camden Yards, where there is a station.

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The typical healthy lifespan of a light rail car is 30 years, Arnold said, meaning Baltimore’s fleet is approaching or has already met that benchmark.

Rail cars typically go through a “midlife overhaul,” a process of significant maintenance and rehabilitation meant to prolong a rail car’s lifespan. For the Baltimore light rail, midlife means 15 years, so ideally the process would have started with the oldest rail cars around 2007.

But a contract for the midlife rehab work wasn’t awarded until 2013, and was supposed to be wrapped by 2018, according to Mass Transit magazine. It’s unclear if the mechanical issues that have sidelined the light rail cars are happening to ones that have already been rehabbed, but Arnold did say that those issues are related to the midlife overhaul.

What will be the effect of recently announced transportation budget cuts?

The MTA has been dealing with a multibillion-dollar backlog of needed rehabilitation work across all of its transit modes that goes back years.

Officials announced proposed cuts to the state’s transportation budget earlier this week, but said that operations for “core service” on Baltimore’s transit lines would not be affected. Arnold said budget cuts won’t affect the planned-but-delayed overhaul of light rail cars, but that complete replacement of the fleet with brand new rail cars could be pushed back.

Daniel Zawodny covers transportation for the The Baltimore Banner as a corps member with Report For America. He is a Baltimore area native and graduated with his master's degree in journalism from American University in 2021. He is bilingual in English and Spanish and previously covered immigration issues.

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