>Metrorail Breaks Down Twice as Often as NYC’s Worst Line

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WMATA posts its service interruptions daily. They also report monthly (PDF) to the Customer Service, Operations, and Safety Committee of the WMATA Board.

I compiled the Metrorail service interruption data for May 2008. My method and categories are described below. The coded data is available here, and the spreadsheet is available here. For a full discussion, see this document.  WMATA has stated that the information in this post is being reviewed for comment.
 
Without further adieu, the data:
 
Miles traveled between failures (more is better):
 
How does Metrorail compare to other transit systems?  The data in the figure above is from the NYC Straphangers campaign (PDF).  Based on some rough figures (6 car trains, 12 mile commute each way, 240 days per year, each delay affecting 2-3 trains in addition to the actual failed one), this means an average WMATA rider could expect to be on a train that is delayed 10 minutes or more three times per year. Compare that to NYC, where it should only happen once or twice per year on the worst line, and less than once per year on the average line.
 
Looking at it another way, the delayed or out of service trains are only 0.6% of all trains. But this means that you’re likely to be delayed in one out of every 180 trips or so, or for the average commuter, about every 4-5 months. When a train is delayed, other trains in the system are also delayed, depending on the severity of the problem. If you assume that three or four other trains are adversely affected, then passengers might expect to experience one delay per month.
 
I think this reflects the kind of service I’ve experienced. I haven’t experienced these kinds of delays in other heavy rail systems, but I will grant you that I ride about 200-300 times more trips on Metrorail than all other rail systems combined.
 
My brother rides BART for his daily commute and does not remember being offloaded ever. My conclusion is that Metrorail probably suffers from higher than typical service interruptions, based on data publicly available from WMATA’s website. Hopefully, I will obtain data for other systems for comparison purposes. I’m not trying to be overly critical of WMATA operations here, they operate a lot of trains and most (92% [PDF]) of them are on time. My commute is affected only on an occasional basis, but it still seems like it’s more often than in other systems with which I have experience.
 
This data is important to the debate about WMATA capital funding (PDF). On the one hand, the lack of capital funding could be contributing to decreased system reliability. On the other hand, system problems run the risk of being perceived as the fault of mismanagement or waste and could make it harder to obtain additional funds.
I have also requested similar service information from MARTA and BART, of Atlanta and San Francisco, respectively. Those two systems, while smaller (in ridership and track mileage), operate similar equipment of similar age.
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About perkinsms

I'm an engineer and father interested in transit, parking and economics.
This entry was posted in calculations, raw data, transit, WMATA. Bookmark the permalink.

5 Responses to >Metrorail Breaks Down Twice as Often as NYC’s Worst Line

  1. Mark says:

    >”an average WMATA rider could expect to be on a train that is delayed 10 minutes or more three times per year.”Honestly, this doesn’t seem too terrible to me. Out of 500 (?) trips, only 3 are delayed? Considering the value of ubiquitous, frequent trains, this seems reasonable. If we assume an average 20 minute trip, plus a five minute wait, then people are spending 12,500 minutes doing train related things each year. Three 10-minute delays is only an extra 0.25%, or the equivalent of increasing the average wait time from 5 minutes to 5 minutes, 4 seconds.

  2. Michael says:

    >Except that other transit systems have much better performance, that’s true. And the affect on ridership is related to the deviation from the mean, rather than the mean trip length.

  3. Mark says:

    >Sometimes(!) mean + x stdevs is what matters.I still think that the standard deviation, or at least the frequency, is reasonable, given that you could be late home once, late to work once, and late on the weekend once, in a year, and I suspect that would be fine.Perhaps other mass transit systems have better reliability, but many do not, and many non-mass transit systems (such as driving 20 miles to work, like lots of people do) have vastly higher variances.Just playing Devil’s Advocate here.

  4. Michael says:

    >WMATA’s asking for $11B in new funding over the next 10 years. People are going to want to know how reliable or unreliable the service is for determining how to react. I think it’s interesting that WMATA reports much better numbers in the annual report (on par with NYC Transit)Can you think of a better way to estimate the reliability based on the data I have? Number of miles total compared to failures = MDBF?

  5. Anonymous says:

    >The average age of NYC’s subway car fleet may now be significantly younger than WMATA’s car fleet. NYC Transit’s new cars are required to meet a MDBF performance figure of over 100,000 miles for a few years after purchase.

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