Increasing Capacity on Metro

Metro ridership has been steadily rising for years. The Orange Line in Arlington and Fairfax, the "Orange Crush," has the worst crowding. In 1994, when I lived near Court House Metro, I could get a seat on my commute into DC. By 2000, I would only occasionally get a seat living two stops further out at Virginia Square. Now East Falls Church is my closest station, and most mornings it's unlikely I'll get a seat. There is no way someone at Court House ever gets one.

Metro has added some 8-car trains, which help. There is a fairly simple operational change that I believe can add capacity at no extra cost. Philadelphia has used this since 1956, and call it A and B trains. New York City called it "skip-stop" until they recently ended the practice.

Here's how it works. During rush hour each train is either an "A" train or a "B" train. Each train skips some stops. "A" trains start at Vienna and skip Dunn Loring and Virginia Square. "B" trains also start at Vienna and skip East Falls Church and Clarendon. (Skipped stops should be the least used stops, and should come in pairs, to balance ridership between the A and B trains).

The trip from Vienna to, say, Farragut West becomes 24 minutes instead of 27, a 10% time savings. The entire trip from Vienna to New Carrollton shrinks from 57 minutes to 54, saving 5%.

That time savings could allow Metro to save cars and run longer trains. There are more than 20 trains operating on the Orange Line during rush hour. Freeing up one train will allow 3 6-car trains to be extended to 8-car trains, thereby increasing the capacity.

The shorter runs could also allow more trains. Right now, Metro can't fit more actual trains through Rosslyn, but one day that might change if they send Blue Line trains up the Yellow Line, change signal technology, or build new river crossings. If it does, or if they try this on a different, less constrained line, Metro could run the same number of physical trains more frequently. Instead of 360 second headways, for example, they can reduce to 342 second headways, increasing the capacity of a line by 5%.

How does this affect passengers? Most will benefit, but some will be inconvenienced. Here are outcomes for commuters to DC from Virginia stations:

• Vienna to DC: 2 stations reduced ride time (BIG WIN!)
• Dunn Loring to DC: Increased waiting time and 2 stations reduced ride time (about a wash)
• West Falls Church to DC: Either 1 or 2 stations reduced ride time (WIN!)
• East Falls Church to DC: Increased wait and 1 station reduced ride time (slightly negative)
• Ballston to DC: 1 station reduced ride time (WIN!)
• VA Square to DC: Increased average wait and 1 station reduced ride time (slightly negative)
• Clarendon to DC: Increased average wait; no time savings (lose)
• Court House/Rosslyn to DC: No change

A small minority of riders traveling to one of the skipped stations also experience increased times waiting for their train. In a few cases, they may actually have to change trains if both their boarding and deboarding stations are served by different trains.

Vienna, WFC and Ballston riders all benefit, Clarendon riders lose about 3 minutes average waiting time, and Dunn Loring and EFC riders may be slightly negative or about even. The three benefiting stations represent roughly two-thirds of the ridership of these 7 stations, while Clarendon represents about 8% of the ridership. Therefore, two-thirds of the riders benefit directly. And everyone benefits from reduced crowding on the trains because of the increased capacity afforded by longer trains.

Plus, this same system could work on the other lines, too, including ones not at maximum capacity. It's probably easiest on the Red Line, since it does not have to merge with another line like the Orange does with the Blue and the Yellow does with Green.

They've been doing it for more than 50 years in Philadelphia. When I lived there (near a "B" station), it was just considered normal operating procedure. If it can work there, why not here?

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Steve Offutt, Arlington Orange Line rider

(This post is cross-posted at steveoffutt.com and Greater Greater Washington, along with almost 50 comments.)

Comments

[Steve Offutt]

Hello Dharm,

Thanks for you comment.
Where I first encountered this system was in Philadelphia, which has
two tracks like Metro, so I would disagree with your premise that it
only works in places with four tracks.  It was my experience that
having the A/B service reduced travel times for the majority of
riders.  It did increase travel times for a minority of riders
(including me), as you point out, so there is an appropriate balance to
find.  In my scenario, average commute times are reduced, so benefits
outweigh costs for riders, even in the absence of any capacity
improvements.

As a long-time Orange line rider, I see very few people disembark at
Virginia Square or Clarendon inbound in the morning or board there
outbound in the evening (which is when I propose the service would be
in effect; not all the time).
Undoubtedly, reducing dwell times can help, too, although I am told
that the real problem is that the Rosslyn tunnel is essentially at
capacity; only x trains per hour can get through--which is a problem
independent of dwell times.

My idea is not a final solution by any means.  There are dozens of
ideas--most of which cost significant money (including yours of buying
million-dollar cars)--that will help Metro deal with its crush of
passengers.  One advantage of this idea is that is very cheap and
easily reversible if it doesn't work, so there's little downside to
testing it.  I'm not positive it will work.  What I do know is that it
worked in Philadelphia in quite similar circumstances, so I don't see
why it wouldn't work here, too.

Thanks again.
Steve

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[Dharm]

This does not make any sense. Other agencies such as the CTA have eleminated skip stop service. It only makes sense in places like New York where you have 3 or 4 tracks which allow for the skipping of stations. In our case, the stations are not all that closely spaced out and there are a significant number of people that get off at the Orange line stations under Wilson so skipping them simply makes anyone getting off at those stations commute longer. Finally, the way the switch at Roffyln is currently set up during rush hour there are two Orange line trains followed by a Blue and delays are bad. Imagine if dwell times at stations are not even then the timings could be thrown off even more. This idea should be quickly discarded to the rubbish bin where it belongs. The only real way to solve the crowding problem is to buy new cars with four doors per side and fewer seats. Dwell time not the number of stops is the limiting factor in how many trains can be pushed through the system.