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| Re: TA is obsessed with CBTC, and ''New'' tech for no reason. (579218) | |||
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Re: TA is obsessed with CBTC, and ''New'' tech for no reason. |
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Posted by Jeff H. on Sun Mar 2 01:18:48 2008, in response to Re: TA is obsessed with CBTC, and ''New'' tech for no reason., posted by trainsarefun on Sat Mar 1 18:58:17 2008. I think what you are missing is that SB is comparing actual CBTCperformance to conventional signal performance in a different time period. Several things have happened since the peak service levels of the 1950s which have cut into the ability of the fixed wayside system. Most of them have to do with trusting, or rather NOT trusting the person in the cab. 1) Automatics were designed to be s/p (stop and proceed) signals. The key-by mechanism of briding the IJ at low speed forced the motorman to come to a complete stop short of the signal, and THEN proceed at RESTRICTED SPEED. Thus closing-in was always possible, regardless of signal spacing. Rules changes 30 rules ago put an end to this practice "officially"...now you needed to call on the radio to key-by. But before the days of event recorders and blame-oriented supervision, experienced motormen often did it anyway to stay on schedule. 2) TA was caught with its pants down in 1995 when the NTSB investigation into the WB accident concluded that emergency braking distances had been allowed to increase substantially beyond the original design assumptions. As a result the overall fleet speed was reduced (doesn't affect tph but schedule speed, and thus trainsets required to meet a given tph) 3) After WB, signal design philosophy became very paranoid. In certain areas (mostly around stations), reduced braking distance margins were allowed based on certain assumptions again centering around motorman competence and willingness to live. These had to be upped resulting in lower throughput. 4) Evidently current rule doesn't permit an in-service train to come partially into a station?! That used to apply only to those trains which were skipping the station or light. The whole premise of station time falls apart if that is the case. 5) Precious dwell time seconds consumed by extra precautions which should not be necessary, e.g. door enablers and pointing at the board. Unfortunately these effects are cummulative over many decades and represent a long-term direction, not the mismanagement of any one particular administration. The TA managed itself into a corner where it needs new signals to survive. You could do the math a certain way and the TA comes out ahead with this approach. An entire generation of operating personnel has been trained to do things a certain way, which is essentially to transfer responsibility from the field personnel to managment. If one were to try to roll back the clock and simply liberalize the practices above, there would be a wreck every week and probably a fatal every year. |
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