Comments on: Under new metric, Transit finds more trains late http://secondavenuesagas.com/2009/10/27/under-new-metric-transit-finds-more-late-trains/ A New York City Subway Blog Mon, 13 Feb 2012 12:58:20 +0000 hourly 1 http://wordpress.org/?v=3.3.1 By: Cap'n Transit http://secondavenuesagas.com/2009/10/27/under-new-metric-transit-finds-more-late-trains/#comment-66120 Cap'n Transit Tue, 27 Oct 2009 23:48:05 +0000 http://secondavenuesagas.com/?p=4144#comment-66120 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. 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.

]]> By: Alon Levy http://secondavenuesagas.com/2009/10/27/under-new-metric-transit-finds-more-late-trains/#comment-66116 Alon Levy Tue, 27 Oct 2009 20:49:28 +0000 http://secondavenuesagas.com/?p=4144#comment-66116 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. 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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