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| Re: 2nd Ave Subway Setback (811605) | |||
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Re: 2nd Ave Subway Setback |
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Posted by Stephen Bauman on Wed Jul 22 06:25:50 2009, in response to Re: 2nd Ave Subway Setback, posted by Easy on Tue Jul 21 21:22:00 2009. Two tracks with less frequent stops is the way to go.That's a prescription for reduced capacity. The number of people per hour a system can carry is the capacity/train x trains/hour. So, given cars and trains of similar size, the system that has the higher service level capacity (tph) will have the greater capacity. There are two determinants to service level capacity: capacity at the terminals and capacity at the intermediate stations. Consider two systems operating at near capacity with different intermediate station philosophies. The first system has frequent stations with fewer people serviced at each station; the second system has half the number of stations each servicing twice the number of passengers. The minimum headway (the reciprocal of service level capacity) for intermediate stations is essentially the sum of: braking time; acceleration time and dwell time within the station. The nominal times for these parameters are 30 seconds each for a minimum headway of 90 seconds or 40 tph. Reduce the number of stops by half and force the passengers to board the remaining stations. The dwell time will at least double. This will increase the nominal dwell time to 60 seconds and the minimum headway to 120 seconds or 30 tph. Want crowded trains? Decrease the number of stations. |
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