You might recognize the concept from transit systems at airports that use glass walls and sliding doors that open only once the vehicle moves in. The technology is also common on subway systems in Asia and increasingly in Europe, but it has not been deployed on a major US transit system.

Now the T might borrow a much higher-tech idea from the other side of the world: building a wall to separate riders from arriving trains.

The boarding process on Boston subway platforms can be so unruly that transit officials have tried taping lines on the platforms to keep new passengers from blocking departing riders.


Platform doors are often seen as a safety measure, to prevent passengers from accessing or falling on active train tracks. But Massachusetts officials see them primarily as a way to bring more order to the sometimes-chaotic boarding and disembarking process. Coupled with other new technology, the doors could even be used to help steer riders to cars with fewer passengers.

“You can begin to create visual cues and visual barriers so that people know where the door’s going to open,” state Transportation Secretary Stephanie Pollack said. “If you’ve ever been in some of the systems in Europe, they even have overhead information that tells you not only where the cars are but which ones are fuller so you can sort of locate yourself on the platform and align yourself with the ability to walk right into a car.”

The impetus for the idea is the arrival of the first new Red Line cars beginning next year — which, unlike the patchwork of cars in the current system, will all have the same dimensions. Because the barriers would be in fixed locations, subway cars have to be a uniform length to align with the openings.


Officials are also planning a full car replacement in the next decade on the Green Line, which currently operates different models. The Blue Line and Orange Line each already have uniform fleets, though the Orange Line is also set for a full replacement in coming years.

The platform doors are included on a draft list of projects the Massachusetts Bay Transportation Authority is targeting for 2040, giving them similar priority status as a planned extension of the Silver Line to Everett and a pedestrian tunnel between the Downtown Crossing and State Street stations. While these projects aren’t guaranteed to happen, that they made it onto the agency’s official planning documents indicates the MBTA is serious about deploying them.

Proponents for platform doors say they speed up boarding — and cut down on delays — by making it clear where the train will stop, and acting as another guide for boarding riders to stand aside to let passengers disembark first.

“Crowding tends to be diminished,” said Charles Moerdler, a member of the New York City transit authority board who has so far been unable to persuade his colleagues to adopt platform doors. “Instead of people spreading out all over the platform, they know that the doors will open in a given place. So they are essentially moving themselves to positioning where the doors will open, and that has the impact of making it a little more disciplined in terms of getting on board.”

It’s similar to another concept tested by the T in recent years, of putting tape on the ground to mark where passengers should stand as doors open. Officials said that system helped speed boarding somewhat, but train doors did not always align with the tape.


And with or without platform doors, subway riders would still need to be taught to stay clear of departing passengers. Pollack said the barriers could include visual cues directing passengers where to stand — but it’s anybody’s guess whether impatient Boston riders would heed the directives.

At this early stage, it’s not yet clear what kind of barriers the T would consider, and whether they would be used across the entire system or on some lines or at certain stations. Some barriers stretch from floor to ceiling, while others are approximately at head height. They are often made with glass, but some makeshift systems simply use concrete barriers or metal fences near platform edges.

Though simple in concept, barriers have unique challenges, Moerdler said. They can be difficult to build at stations with curved platforms or other unusual contours, and they require proper maintenance to ensure the doors open and close as needed.

Also, trains must stop at very precise locations so the doors on the cars and the platforms are perfectly aligned when they open. The T expects to install new signal systems in the coming years that will ensure trains stop at the exact location of the door openings.

In Hawaii, the Honolulu transit system will install shoulder-height platform doors on a new elevated train system opening in 2020. The cost there is pegged at $1.3 million per station, but it could be much more in older subways where stations may have to be retrofitted to accommodate the doors. In Montreal, transit officials once estimated such a project would cost about $7.5 million a station.


Hawaii officials said the barriers are primarily for safety reasons.

“Any life saved would be worth every penny we put into the purchase,” said Bill Brennan, a spokesman for the Honolulu transit system.

On the MBTA, there have been 15 deaths on the subway system since July 2014, compared with 47 on the commuter rail system over the same period. Many, but not all, rail deaths are suicides.

Patrick Sherry, a University of Denver professor who studies railroad safety, said that because so many of the deaths on the commuter rail system are away from stations, it’s reasonable to instead focus the barrier systems on subways. Also, subway platforms are more crowded, making it more likely that a passenger might accidentally fall onto the rails, he said.

Sherry said more transit systems in the United States should install the technology, but they also must work with public health officials and community groups to address underlying causes of suicide, such as by directing vulnerable people to hot lines and mental health resources.

For more information about recognizing the signs of suicide and seeking help, visit www.mass.gov/dph/suicideprevention or www.suicidology.org. Additionally, the Samaritans will talk at any time, by phone or by text, at 1-877-870-HOPE (4673). The National Suicide Prevention Lifeline is 1-800-273-TALK (8255).


Adam Vaccaro can be reached at adam.vaccaro@globe.com. Follow him on Twitter at @adamtvaccaro.