Home Asides Under new metric, Transit finds more trains late

Under new metric, Transit finds more trains late

by Benjamin Kabak

In an effort to improve its internal metrics, New York City Transit recently reevaluated the way it judges on-time train performance. Now that the agency is counting delays brought about by service changes or construction and maintenance disruptions, the numbers look ugly. According to a report released today, Transit’s on-time rate has plummeted to 50 percent on the weekends and 75 percent during the week. “I actually have a couple of horror stories here with respect to the different lines that have particularly low absolute on-time performance,” NYC Transit President Howard Roberts said, referring to the 1 line which had been slowed due to the ceiling collapse at 181st St.

While I understand the need to measure on-time train performance, I have to wonder if this is the right metric. New Yorkers don’t really expect subway trains to run “on time” because the schedules, while available, are rarely used and aren’t considered gospel. The better indication of on-time performance involves train wait times. If I just miss a B train during the day, I expect to wait 8-10 minutes for the next one. If I’m waiting longer than that — no matter what time the schedule comes — I consider the next train to be late. I also come prepared for longer headways on the weekends considering the extent of the service changes. My approach, though, is simple: If the trains run on time, great; just don’t make me wait longer than I ought to for the next one.

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2 comments

Alon Levy October 27, 2009 - 4:49 pm

When a train or bus comes every 8-10 minutes, I want to know exactly when it comes so I know if I’ve missed it. When it comes every 4 minutes it’s less important, but it’s important to make sure the trains are spaced exactly 4 minutes apart. Otherwise, wait times increase rapidly. The problem is that, if half the trains come 6 minutes after the previous trains and half come 2 minutes after, then three quarters of the riders will have waited for a 6-minute train, for an average headway of 5 minutes. This also means the 6-minute trains will be much more crowded, increasing dwells and causing further delays.

For the 1, schedule adherence is less important than consistent headways. But for trains that share tracks with other trains, it’s necessary for scheduling purposes. If NYCT can’t trust that the 2 will arrive at the 142nd Street Junction halfway between the preceding and following 3 trains, some trains will have to be delayed.

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Cap'n Transit October 27, 2009 - 7:48 pm

Yes, but if the trains have eight minute headways and all of them are exactly eight minutes late, how can you tell? Rather than having a “late” metric for frequent lines, they should get points off if a train arrives in between scheduled times, as in Alon’s example, and more points off if one is missed altogether. Maybe one point off for bunching, because it wastes time and money.

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