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| Re: W train returning when Phase I of the 2nd Av subway opens in December 2016?. (1386587) | |||
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Re: W train returning when Phase I of the 2nd Av subway opens in December 2016?. |
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Posted by Stephen Bauman on Mon Feb 22 18:25:45 2016, in response to Re: W train returning when Phase I of the 2nd Av subway opens in December 2016?., posted by randyo on Sun Feb 21 18:27:31 2016. The problem with paper railroading vs the real world is that while running times between locations are often in odd amounts such as 2 min and 15 sec, scheduling even computer generated can only be done to the nearest half minute.This is an example of NYCT's ineptness. One of scheduling's commandments is not thou shall work in 30 second increments. Indeed, if you look at IRT schedules from the early 1900's, you will see they calculated arrival times in 15 second increments. All this without computers - only pencils and green eye shades. (Actually they used graph paper, T-Squares and triangles.) One of the first tasks in analyzing an engineering problem is to determine what precision and accuracy is required. Let's look at the merge problem. It takes approximately 1 minute for a train to clear a switch. If trains are operating on 2 minute headways, there will be 1 minute of free time between trains. If each train is within 30 seconds of its scheduled arrival time, there will not be a merging conflict. For 90 second headways (40 tph), the envelope is 15 seconds. Neither can be accomplished, if schedules are resolved to 30 second accuracy. Other systems do operate at close to the nominal 40 tph. Schedules are resolved down to the second. There are clocks in each station to alert the crew whether they are ahead or behind schedule. They trust the crew to alter dwell time accordingly. NYCT has a lot to learn. |
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