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| Re: W train returning when Phase I of the 2nd Av subway opens in December 2016?. (1386711) | |||
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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 Tue Feb 23 19:42:21 2016, in response to Re: W train returning when Phase I of the 2nd Av subway opens in December 2016?., posted by randyo on Tue Feb 23 15:16:57 2016. Creating schedules with running times resolved with greater precision and accuracy than 30 seconds is a necessary step to operating at 30-40 tph without merging conflicts. Whether the ability to key-by is necessary to maintain 30-40 tph isn't germane to whether such schedules are required.Was keying-by required to maintain 30+ tph? There are 3 important reasons why it wasn't used. First, the schedules were created so that every train saw nothing but green signal aspects. That's what the graph paper, T-squares and triangles (and Euclid's 5th postulate) guaranteed. Second, braking is one component of headway. Keying-by at slow speed increases braking time. Minimum headway is based on a much shorter time than keying-by provides. Third, the practice of keying-by to maintain schedules was banned by the Transit Commission in 1929. The only reason for keying-by was to pass a broken signal. I will be the first to admit that 30+ tph could not be maintained in the presence of broken signals. I have done what were and maybe still are referred to as “replacement time” checks to determine the actual time it takes for a train to fully clear a station and the followers to enter and it is usually more than the one minute you cite. What exactly is your definition of "replacement time" and how did you measure it? |
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