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| Re: Crowley Wants (7) Train to LaGuardia Airport ? (1163004) | |||
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Re: Crowley Wants (7) Train to LaGuardia Airport ? |
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Posted by Stephen Bauman on Thu Jun 21 12:41:28 2012, in response to Re: Crowley Wants (7) Train to LaGuardia Airport ?, posted by Outside the Box on Thu Jun 21 11:48:30 2012. They also used to run shorter trainThey ran 11 car trains after the 64-65 World's Fair. They ran 36 tph until the financial crisis of the 1970's. They ran 9 car trains in 1954, when the TA documented 36tph operation in their annual report. The difference in train length, means the leader must travel further to clear the signals behind him when leaving a station. The two extra cars comes to 102 feet. At 30 mph, this comes to 2.3 seconds additional headway time. If there were no recovery time for 36 tph operation, the extra length would reduce service levels to 35.3 tph. key by red signals. That's a red herring. Keying by was not necessary to maintain peak service levels. If you run a simulation, you will discover that 40 tph operation is possible without encountering even a yellow signal. Current emergency braking performance seems to be less than in the past. That was certainly demonstrated by the NTSB tests after the Williamsburg Bridge crash. However, the effect of poorer emergency braking performance on service level capacity is easy to calculate. In fact, it's exactly the same calculation made above for longer trains. Emergency braking rates determine minimum spacing between trains. The more important braking factor in determining maximum service levels is service braking rates. These have not changed - as demonstrated by the NTSB tests after the Williamsburg Bridge collision. Organizational practices might had been better then too. Just having crew in place before trains are pull into terminals speed up turnaround time, esp at 111th st and Willets Pt. +1 However, that's neither an equipment nor a safety issue. It's simply an acknowledgement that the people in charge should know what to do. BTW, don't leave out Main St and Times Sq, where crews have to be waiting. Running 40tph requires low station dwell time. The time allotted seems to be 30-40 seconds, depending on train performance. 40 tph means 90 second headways. The 90 seconds consists of 30 seconds of braking time, 30 seconds of acceleration time and 30 seconds of dwell time. If you bother to time the actual acceleration and braking times, you will find that both come in between 20 and 30 seconds. You need better railcar interior and door layouts than what is present on A division for that. Division A interiors have been consistent since the introduction the the LV-WF cars in 1939. They ran 36tph with R12/14/15's and R33/36's. The interior dimensions are virtually identical to the R62's currently operating. The interior designs are not that much different than the R142's that would be used with CBTC. |
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