In Boston, subway passengers are reminded to stand back from the platform and watch the train doors as they close. But unlike some major rail systems, the MBTA doesn't warn riders that the gap between the platform and the train could also pose a risk.
Last Friday, a 45-year-old woman was injured as she got off an Orange Line train when her left leg became caught in the gap, causing a deep cut. Officials said the gap was about 5 inches. Several passengers helped free her by pushing the train away from the platform.
Because the space between the platform and the train is so small — usually less than 4 inches — and injuries are rare, the MBTA has not felt a messaging campaign is necessary, said Joe Pesaturo, an MBTA spokesman.
A 4-inch gap is what national standards call for at train stations, said Carl Berkowitz, a New York-based transportation expert who specializes in accidents involving pedestrians, passengers, and bicyclists.
"Using the word 'gap' can underscore the size of the space," Berkowitz said. Gaps in the New York City rail system can be as wide as 14 inches, he said.
In 2016, when the newly renovated Government Center station reopened, a stenciled message to "Mind the Gap" — a phrase best associated with the London subway system — was added along the edge of the platform. The reminder was placed there because the platform is on a curve, causing larger gaps in certain areas, Pesaturo said. The Green Line also uses two distinct trolley designs, varying the space between cars and the platform.
The London subway system launched its signature "Mind the Gap!" audio message in 1969. But Mike Horne, the author of a book series about the 11 lines of the London Underground, wrote that the warning likely dates back to at least the 1920s, when trains with doors spaced evenly throughout the cars, not just at the ends, were introduced.
In those days, the warning was likely shouted out by train workers. Photos indicate that written warnings were added to stations in the 1930s.
Variations on the phrase are used in railway stations around the world, from Paris to Tokyo to Singapore.
In addition to audible warnings and visible cues, physical changes to trains and platforms can also decrease gaps, Berkowitz said. They include extending the bottom edges of railcar doors and installing strips called rubbing boards, changes that can narrow the gap without causing damage to the train if it sways on the track.
When an 18-year-old woman was killed in 2006 after falling into an almost 8-inch gap on the Long Island Rail Road in Queens, New York's Public Transportation Safety Board conducted a special study, "Managing the Risk of Station Platform Gaps." The study prompted major changes to the commuter rail system, including physical elements to narrow the gap and audio and visual warnings.
Since then, there has been a significant decrease in gap-related incidents on the Long Island Rail Road, Berkowitz said.
Emily Williams can be reached at emily.williams@globe.com