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| Re: TA is obsessed with CBTC, and ''New'' tech for no reason. (578866) | |||
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Re: TA is obsessed with CBTC, and ''New'' tech for no reason. |
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Posted by trainsarefun on Sat Mar 1 11:30:21 2008, in response to Re: TA is obsessed with CBTC, and ''New'' tech for no reason., posted by Stephen Bauman on Sat Mar 1 09:29:08 2008. However, the existing wayside system with "discrete" trippers permits service levels far in excess of what is currently operated.I don't know that in practice that's true. It seems like a lot of the benefit of 'station time' ('ST') signals is not given any effect because exactly where blocks are, for good reason, shorter - approaching and through stations - because the following train cannot close in behind a leading train until the rear of the leading train has cleared the starting (leaving) signal out from the station, so instead of the blocks being the shortest encounters, it seems that practically the block is the longest because the following train is stopped at the entering signal to the station not yet in the station, and the leading train is over a train length away by the time it clears the station's leaving signal. Based on this sort of observation, I'd hazard to guess that a lot of the benefit of shorter blocks exactly where they'd do the most help in moving things along at low speed is thereby eliminated, since the station seems to practically be treated as a long block longer than a train length. The reasons for this? Well, maybe they're worried about passengers trying to board the following train before it has fully platformed and actually opened its doors, but I think we can shoot this reason down very fast, since from our operating friend Robert, we know that this is done on the Canarsie Line, and there's nothing different between CBTC and the traditional signal system that would prevent cretinous behavior by passengers. The second reason that comes to mind, to borrow an expression of Jeff's, is that they're worried about 'suicides', and thus the procedure in effect, although I'm given some pause by this, since even under the procedure in place, the engineer hell-bent on collision could just pass by the station, gathering speed all the while, and plow into the train ahead of her, or at least giving the emergency braking abilities of her train some testing, something that I gather CBTC wouldn't allow the engineer to do. But then, CBTC is seemingly guarding against death wishes; maybe that's the goal, though? The theoretical service level improvement for CBTC will be less than 5% over the current system. At least on the Canarsie Line, unless there's automatic control of trains operating at higher speeds into and out of the terminals, I gather that we're agreed that while, say, CBTC will leave it theoretically possible to run in excess of 24 tph - I'll trust your numbers for terminal capacity, although from what I've been reading on here, possibly the Canarsie terminal wouldn't have permitted 24 tph in capacity, but on that end of the line, I suppose that one could maybe get out of it by saying that some trains would be short-turned at Myrtle Av (somehow, let's not bother with how, now) - the 8th Av terminal capacity would set the actual capacity limit. In that respect, it seems that part of improving capacity on the line would have to include construction of tail tracks at the terminals. UNLESS automatic control of trains would result in more actual terminal capacity. I suppose that will become clear if the line sees service in excess of 24 tph. |
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