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| Re: LIRR East Side Access / Roosevelt Island F Station (557076) | |||
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Re: LIRR East Side Access / Roosevelt Island F Station |
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Posted by straphanger9 on Mon Jan 21 07:34:29 2008, in response to Re: LIRR East Side Access / Roosevelt Island F Station, posted by Russ on Mon Jan 21 05:16:19 2008. True, that would avoid Queens Plaza, but you'd still have problems at 36th St. The (express) and the  (local) would both be switching onto Queens Boulevard from the same origin track (the one from 21/Queensbridge). Therefore if EITHER an (waiting for  to clear express track) or (waiting for  or  to clear 36 St. station) were stuck on that approach track, both the and would be delayed. Furthermore, while the enters 36 St., and service is delayed.Put this in rush hour with one of those "sick passenger" conditions, and because of the Queens Plaza issue between the and (with the local stopping on the express track) that exists independent of any changes to the , and you now have delays on every single Queens Blvd. line. Only way around those kinds of delays is to run everything express around the incident train, but then you'd have as many as 5 services using the express track and everything committed to the express until Roosevelt Ave. Operationally it just leaves no room for error.Optimum TPH IS probably around 40tph - if the platforms are empty save for a handful of intelligent and alert passengers, no one holds the doors, and all equipment is in perfect order. However, this is never the case. There has to be a bit of room for error such that delays can be filtered out, not go on forever or extend down multiple lines. And that's why 30tph is about as reasonable a standard as possible on those local tracks. Furthermore, in response to what you said to RonInBayside, the  // are able to "pull it off" (ie run three trains on one track) because of the headways built into the scheduling. For comparison...During rush hours: service is 7-8 minutes (rush hour), and 10 minutes (midday). service is 6 minutes (rush hour), and 10 minutes (midday). service is 10 minutes (rush hour and midday)There are fewer trains. In a typical rush HOUR, that means there'd be 6 's, 10 's, and 7-8 's...that's 23-24 tph on those tracks. And none terminate on the shared trackage (60th St. tunnels - TSQ before the goes express). Lower Manhattan never sees 3 services on the same track because when the is running, the is via Bridge. And with the terminating at Whitehall, that makes a lot of sense. To prove this, even with the ending at Whitehall, delays at Rector can be common...waiting for that middle track to clear at Whitehall.Meanwhile, on Queens Boulevard: service is 4 minutes (rush hour), and 7.5 minutes (midday) service is 4 minutes (rush hour), and 7.5 minutes (midday) service, as above is 6 minutes (rush hour), and 10 minutes (midday) service is 6 minutes (rush hour), and 10 minutes (midday)Peak, that's 30 tph on the express (just about capacity - Chris R16/R2730, you were right) and 20 tph on the local. Which means that the (which like the and runs 6:00/10:00), would put the line to EXACTLY, capacity.But then you factor in 2 trains turning at CTL, and the complications of the interlockings before 36 St., as well as the trickle down of delays to Queens Plaza, and the necessary slowdown in operation resulting from all this, and you're over capacity. To put it simply, 2 of every 3 trains has exactly 120 seconds to pull into CTL, discharge passengers, announce last stop, pick up a switchman, make sure no geese on the train, close down, punch for the relay, get the lineup, and move out...and those signals into CTL have to clear to restart the clock on the next train coming in. So combine that issue with the issue of both tracks at / slightly beyond capacity, if there's any service disruption - if a local needs to skip a few stops, or an express needs to scrape the wall, then that will lead to major delays along the entire line, and probably one of Railman's "mushroom cloud" posts. :P |
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