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Metro FAQ: Why does Metro run express trains in one direction during single-tracking?

Twice this week, attempted suicides have caused single-tracking during busy times. In both cases, Metro sent trains in one direction express through the single-tracking zone. Why would it do this?

The Metro system has two tracks on each line. There are interlockings, where trains can change tracks, every so often. Whenever they single-track, the track that's open has to take turns carrying trains in each direction. Generally, Metro will send a few trains going the same direction through at once and then reverse the track.


A diagram of how single-tracking works. Graphic by the author.

Of course, the reason that delays accrue quickly is because it can take a train 4 or 5 minutes to clear the single-tracking section. While a train goes through in one direction, trains going the other direction are holding (and stacking up) on the other end.

On Wednesday, when a person jumped in front of a train at Rhode Island Avenue just before the start of the evening rush hour, Metro sent outbound Red Line trains through normally. But inbound trains were run through without stopping. By doing this, Metro mitigated the delay.

This is because Metro trains lose about a minute stopping at each station. The train is generally stopped only for about 30 seconds, but there's also the time lost to deceleration and acceleration.

The normal travel time between Union Station and Rhode Island Avenue is about 4 minutes. If Metro sends 2 trains through in the same direction (with the second about 90 seconds behind), the time it takes Metro to reverse the single-tracked section is about 6-7 minutes.

That means the cycle time is about 12-14 minutes.

But if inbound trains skip intermediate stops, they can save time, which reduces the cycle time. If outbound trains take 6 minutes to clear, but inbound trains can do it in 3 or 4 minutes, the cycle time is reduced from 12-14 to 9-10 minutes.

It does create additional delay for anyone boarding or alighting at those stations, at least those going in the direction skipped. But anyone going through the zone saves time.

However, Thursday's incident at Waterfront was more problematic. Metro sent northbound trains through from Navy Yard to Archives without stopping. That meant that northbound Green Line trains skipped L'Enfant Plaza, and riders couldn't transfer to or from the Blue or Orange lines. A passenger at Waterfront who wanted to catch the Orange Line would first have to take a Branch Avenue train to Navy Yard, then a Greenbelt train to Archives, then a Branch Avenue or Huntington train back to L'Enfant Plaza.

Metro did try to mitigate problems somewhat by running all Yellow Line trains to Greenbelt, and those trains did stop at L'Enfant. But it was still a mess. Of course, given the delays, it likely would have been a mess no matter what Metro did.

But aside from the L'Enfant Plaza issues, skipping stations in one direction looks like a promising way to mitigate delays during an unplanned service disruption.

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 Greenbelt. Hes a member of the American Institute of Certified Planners. He is a contract employee of the Montgomery County Planning Department. His views are his own and do not represent the opinion of his employer. 

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I love "explainer" pieces like this one. They teach me things that make me look smart at cocktail parties! My friends all look to me as the Metro "expert", but really if they read GGW, they'd know as much as I do! Thanks, Matt!

by Aimee Custis on Mar 7, 2014 11:28 am • linkreport

During the Red Line issue on Wednesday, they also turned around every other Glenmont bound train at Judiciary Square, so that service up towards Shady Grove (this was in the 3:30 timeframe, so just as rush hour was starting) would not be overly affected. I thought that was a very smart move on Metro's part.
The only downside was that the best "announcement" was a WMATA employee standing up on the mezzanine at Gallery Place with a bullhorn. There were transit cops there for crowd control, but they weren't clued in as to what was going on, and the announcements from both the trains and the station speakers were barely audible.

by Joe in SS on Mar 7, 2014 11:29 am • linkreport

So here is my question isn't there a Rail Yard between Noma & Rhode Island Ave why not have trains switch tracks there ? There has to be some tracks at the Yard that allows tracks to switch tracks.

Also Rhode Island Ave was a terminal so there has to be a switch track somewhere near it when going toward Noma.

Heres to hoping that the next time that build a line they add sliding walls like many other systems have.

by kk on Mar 7, 2014 11:41 am • linkreport

@kk

There is a rail yard between NoMa and Rhode Island Ave, but it's really inefficient to switch trains there because of the way it's configured. If you look at it in google maps, you can see that the only way to switch from the northbound to the southbound track is to enter the yard, double back, double back again, and then exit.

Also, maybe since Rhode Island Avenue was never intended to be a terminal station permanently, they built the switch track to the north of the station.

by japanesehamantashen on Mar 7, 2014 11:58 am • linkreport

Seem to me you can mitigate the problem by sending a bunch of trains through as express and letting the last one make stops. Or, let the first train make a stop at the far station, and the second train at the close station.

Sure that costs some time, but it will get people to those stations.

You have to make good announcements though. Which is where WMATA will fail.

by Jasper on Mar 7, 2014 12:13 pm • linkreport

Anyone boarding at Waterfront wanting to get onto the orange or blue eastbound last night should have been directed to walk to L'Enfant.

Does sound like it was a small number though, if that my my evening commute I would walk to L'Enfant any day it wasnt raining.

by Richard on Mar 7, 2014 12:20 pm • linkreport

I think this only makes sense if there's a significant imbalance in the direction of travel at the affected station(s). That's probably something they could figure out in advance and work into their emergency operations plan.

by JohnB on Mar 7, 2014 12:44 pm • linkreport

@Richard,
I remember seeing the rail twitter feed showing bus service to use between M Street/Waterfront and L'Enfant.

by Transport. on Mar 7, 2014 1:12 pm • linkreport

@Jasper

I've been on a RL train that was expressed through 2 stations of single tracking, with announcements that the train behind us would make all stops, so it can/has been done. (I remember seeing a lot of Metro tweets describing the express...but your point about announcements is totally true.

It may be a rare occurrence though.

by Rob K on Mar 7, 2014 1:30 pm • linkreport

@ Transport

Another thing that could help when there are big delays with a rail line make buses that travel near the station and other stations nearby free around the effected area.

In the case of Rhode Island Ave & Noma that would not work hardly any buses go by Noma but for Waterfront they could have the 74, A9, V7 & V9 free between Waterfront, L'Enfant Plaza & Navy Yard so that anyone boarding between those stations could get on free.

by kk on Mar 7, 2014 1:35 pm • linkreport

I think they chose to express through L'Enfant to limit the effect on the YL line. Inbound YL trains had to share the track with inbound and outbound GR trains. Allowing inbound GR trains to stop would have increased wait times for YL trains.

Having trouble figuring out why they chose to express the inbound rather than the outbound GR though...

by DC Transit Nerd on Mar 7, 2014 1:39 pm • linkreport

For the relative size of Metro, I would hope that for an incident (of whatever nature) occurring at any particular spot they have pre-set plans on what they will do. So for a suicide attempt, signal issue, broken track etc where the recent Rhode Island incident occurred, Metro would have set plans (day and time dependent) to express trains in X direction, allow 3 to pass, etc.

by JDC on Mar 7, 2014 2:02 pm • linkreport

Or if we didn't have the bs transfer penalty then taking the bus to a different station and then getting on the train would be free!!!!

by MLD on Mar 7, 2014 2:05 pm • linkreport

@kk

The reasons why using the trackage on Brentwood Yard to crossover trains is not practical are:

  • The yard trackage is restricted 15 MPH
  • Movements would need to be coordinated by the yard tower
  • Central control can not see where the trans are withing the limits of the yard

by Sand Box John on Mar 7, 2014 2:11 pm • linkreport

@ Rob K:I've been on a RL train that was expressed through 2 stations of single tracking, with announcements that the train behind us would make all stops, so it can/has been done.

Good to hear that. I wonder if it was planned or mostly spontaneous.

your point about announcements is totally true.

Occasionally, the blue line bypasses Arlington Cemetery. Announcements are awful, often only announced after the doors close. Or only given from the riding train, instead as a station announcement.

Anyway, announcements are not metro's best side. It still happens regularly that trains depart from Franconia-Springfield during rush-hour with the color of the train only being announced while or after the doors close and the train departs. How hard is it to announce the color of the train, wait 15 seconds and then close the doors? That should not matter even if the train is holding up another train.

by Jasper on Mar 7, 2014 3:12 pm • linkreport

@Transport - People were definitely using the buses they advertised; the 74 is normally fairly easy to get on and get a seat from L'Enfant south, but it was packed last night, and we had to skip at least one stop because the driver had no one getting off and no room for any more passengers.

by Moose on Mar 7, 2014 3:34 pm • linkreport

@Jasper Arlington Cemetery station closes at 7pm Oct-Apr and 10pm Apr-Sept. This is a noted part of the schedule, so I'm not sure it's necessary to make an announcement any different than regular service announcements. Unless of course you mean that they skip the stop during the day...

by DC Transit Nerd on Mar 7, 2014 3:50 pm • linkreport

Well done as always, Matt. I was coming inbound on the YL during this, and noticed they were trying something different.

I've wondered the same thing about using Brentwood Yard as a crossover of sorts. While there is a crazy amount of switches there to route anything pretty much anywhere (it does look like there are proper turnouts for NB<>SB, sort of), it makes sense that the yard tower control and the speed limit makes it unfeasible.

Cool stuff.

by Rich on Mar 7, 2014 4:30 pm • linkreport

@Rich

Actually there is not a crazy amount of switches, depending of the movement trains would only have to go through 2 crossovers.

I also for got to mention, none of the track in the yard are configured to transmit speed commands, hence the reason why the trains would be restricted to 15 MPH, trains would also have to come to a complete stop after losing speed commands before proceeding on at the restricted 15 MPH limit and WMATA's operational rules prohibit the movement of passenger carrying revenue train on yard tracks.

by Sand Box John on Mar 8, 2014 1:39 pm • linkreport

They should use this same feature to run express trains during regular rush hour, to connect the core with the periphery. e.g. on Red Line, express Silver Spring to Union Station, and then again Dupont to Bethesda.

by SJE on Mar 10, 2014 12:17 pm • linkreport

I was stuck waiting on a Yellow south toward Huntington. They ran two or three green lines before the Yellow and then it was a Rush Plus to Franconia. Why on earth they would continue running a rush plus to Franconia when they had significant backups on the Green/Yellow lines was beyond me. I hopped on the Franconia Yellow Rush Plus thinking at least the platforms in Alexandria won't be crowded, but right before we got to Braddock Road, WMATA's wisdom prevailed and that Rush Plus train was changed to a train to Huntington (albeit, I wonder how many people didn't board it like I did because of the Rush Plus).

However, I still don't grasp how it made sense to have any rush pluses in this encounter because you had the Blue Line working fine and your Yellow Line was so backed up that you would be lucky to even clear half of the normal number of Yellow Lines to Huntington at that hour. So the solution should have been to say no RP here and that due to the delays, if people were headed to Franconia, they should simply head over to Metro Center. Honestly this would have been faster for them and I imagine many did.

by Brad on Mar 10, 2014 3:49 pm • linkreport

My Yellow Line train from VA to Greenbelt did STOP at L'Enfant for nearly 5 whole minutes, but did NOT let anyone off in all that time! Had to go to Archives, get onto the southbound train and wait for three whole other northbound Green Line trains to come through, unload, and on-board the southbound before we got to leave for L'Enfant again. And then we got off on the exact same side of the platform that we had lingered on for 5 minutes without letting anyone off or on. So then there were five-trains worth of people that had to alight.

So I guess there were time savings for the 200 people on the three northbound Green Line trains, but not for those on my Yellow Line, and not for the thousands of people on those same three Green Line trains trying to get to L'Enfant.

I think the difference between a TRANSFER station and a non-transfer station need to be taken into account. Because at least the MAJORITY (if not nearly all) of the passengers gets off at a transfer station rather than goes through it.

Also it was absurd for my Yellow Line to STOP at L'Enfant for 5 minutes and not let anyone off.

Or maybe I'm just not getting it.

by C.C. on Mar 11, 2014 12:34 pm • linkreport

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