“This train will not service Brookland.” If you’ve ever ridden Metro during a delay, you’ve probably heard some variation of these words. That’s because Metro is “expressing” your train, meaning it’s skipping stops to recover.

Graphic by the author.

We recently discussed “schedule adjustments” as a way Metro tries to mitigate delays. While schedule adjustments keep headways more even, which both guards against overcrowding and bunching as well as mitigates waits for people ahead of delayed trains, skipping stations allows the delayed train(s) to catch up.

Small windows of time can make a systemwide difference

Skipping a station can save a train about a minute. Every minute counts, both for minimizing overall delays in the system and keeping delays from creeping into the opposite direction.

In the graphic above, if the delayed train were 11 minutes behind and ran express through, say, NoMa and Brookland, it’d make up two minutes on its way to Fort Totten. It would also increase the gap from the train behind from one minute to three minutes.

This technique is also used to cut delays down during unscheduled single-tracking. We explained that use last year.

When they reach the end of a line, most trains turn and run in the opposite direction. There is generally a scheduled layover (called “recovery time”) that lasts between half of the headway and the full headway.

That means a train with a scheduled layover of six minutes has that amount of time before it needs to return inbound. If it’s 10 minutes late, it’s going to be delayed in the other direction even if it turns around and leaves immediately when it reaches the end of the line.

What about passengers whose stations get skipped?

Of course, the cost of skipping stations is that passengers who want to board or alight at the skipped station have to wait for the next train, which can cost them a few minutes.

Most of the time, though, trains are stacked up behind the delayed train, and when that’s the case the extra wait is only a minute or two. While it’s inconvenient for passengers who need to get off at one of the stops their train is skipping to disembark and then take the next train, the actual delay is rarely huge.

Metro usually only skips more lightly used stations. I’ve been riding the northern end of the Green Line daily since 2007. When train operators are told to skip stops there, it’s almost always West Hyattsville and/or College Park. They almost never skip Prince George’s Plaza because so many more people use it than the other two. They don’t skip Fort Totten because it’s a transfer station, and Greenbelt can’t be skipped because it’s the terminal.

Tagged: metro, transit, wmata

Matt Johnson has lived in the Washington area since 2007. He has a Master’s in Planning from the University of Maryland and a BS in Public Policy from Georgia Tech. He lives in Dupont Circle. He’s a member of the American Institute of Certified Planners, and is an employee of the Montgomery County Department of Transportation. His views are his own and do not represent those of his employer.