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| Re: Underbuilt IND? (1139966) | |||
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Re: Underbuilt IND? |
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Posted by Stephen Bauman on Thu Feb 16 07:05:17 2012, in response to Re: Underbuilt IND?, posted by Outside the Box on Wed Feb 15 19:18:06 2012. There is still the human element called passengers that can affect station dwell time.90 second headways consist of 30 seconds braking; 30 seconds of acceleration and 30 seconds of dwell time. Dwell time is defined as the interval between when the doors open and the trains starts moving again. That 30 seconds is sufficient, if service levels are adequate to meet demand. The old 3rd Ave El also ran shorter consists than current IRT. The MUDC's also had acceleration and braking rates that were roughly half that of current IRT equipment. This more than compensated for the extra length of today's consists. Running 10 car trains at 90 sec headways require very strict headway keeping. Operating at the intermediate station service level capacity is fairly easy. The signal system, which is designed to prevent collisions, will also act as a supervision system. It's when trains operate at less than the intermediate station service level capacity, that a separate supervision system is required. The Moscow Metro (40 tph operation) has clocks that allow crew to keep station dwell to a set time frame. NO!!! The clocks in the Moscow Metro tell the crew how far behind they are from their leader. Similarly, the Paris Metro uses clocks at each station to tell the crew when to depart. In both these instances, they have eliminated the problem of accumulated errors inherent in a system based on dwell time clocks. |
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