Brooklyn-bound (A) (C) train spacing

[geoking66]

I was at York Street in the early afternoon waiting for a Manhattan-bound and in the other direction I noticed, in sequence, , , and trains pass by and scheduled literally right on top of each other. I'm pretty sure the just got out of the station before the came in. As a regular Lex rider, this surprised me, since I've barely seen anything this close even during rush hour. I'm curious as to how such close spacing could be achieved on a fixed-block system.

[Abba]

I was at York Street in the early afternoon waiting for a Manhattan-bound and in the other direction I noticed, in sequence, , , and trains pass by and scheduled literally right on top of each other. I'm pretty sure the just got out of the station before the came in. As a regular Lex rider, this surprised me, since I've barely seen anything this close even during rush hour. I'm curious as to how such close spacing could be achieved on a fixed-block system.

 

Well they each run like every 10 min.So there is a train like every 2.5 min or so.

[TwoTimer]

Yup, you're just not used to seeing so much service in the IND. Same signal setup as in the IRT, its just such service is actually scheduled. Have you seen the Lex during Plan 4 on weekends (snowstorms) when the are all local? Same thing.

[Amtrak7]

Yup, you're just not used to seeing so much service in the IND. Same signal setup as in the IRT, its just such service is actually scheduled. Have you seen the Lex during Plan 4 on weekends (snowstorms) when the are all local? Same thing.

 

So that means that the Lex can fit a couple more trains during rush hours, unlike what the MTA claims?

[R68 Subway Car]

They evenly space trains to avoid them bunching together.

[geoking66]

Yup, you're just not used to seeing so much service in the IND. Same signal setup as in the IRT, its just such service is actually scheduled. Have you seen the Lex during Plan 4 on weekends (snowstorms) when the are all local? Same thing.

 

I'm guessing platform length has something to do with it as well, considering 90 feet (or almost two IRT or one and a half IND cars) makes a big difference in perceiving headways.

[TwoTimer]

So that means that the Lex can fit a couple more trains during rush hours, unlike what the MTA claims?

On weekends, jerome and pelham trains run on 8 min headways, dyre trains 12 to 15. All combined, its about a train every three minutes or so, roughly rush hour frequency.

[MikeGerald]

The subway system as built in 1904 and extended since then was and remains capable of a train arriving every 2 minutes. This is two-minute headway standard was established for all of the subway lines built since then. In 1904 the fixed block signal system was a technological marvel, where the interlocking junctions were protected, and the signal / switch system worked hand in hand with each other, to enforce train and driver behavior.

 

When while the subways today, except for certain sections (#7 line, E and F lines in Queens, Lexington Avenue #4, #5 and #6), generally do not have scheduled trains running every 2 or 3 minutes - the systems are capable of such feats. Now there may be certain sections of routes - say the Cranberry Tunnel for the A and C lines at am rush hours, or the 60th Street-BMT tunnel to/from Queens -- may have trains every 2 or 3 minutes apart at the height of the am rush hours - most lines do not have that frequency of service.

 

One thing that has changed over the years or decades is the speeds obtainable by the trains, and the efficiency of the braking system - which has and effect on the spacing of trains, and the distances between them. In the past many trains were allowed to "key-past" some red-signals to help relieve congestion, however newer rules and practices these days have cut down on the amount of "keying by" a red signal.

 

In any case just because a particular line (say the C train) is scheduled for trains every 10 minutes, does not mean that the whole line (as in the signals/tracks/switches) is only capable of running a train every 10 minutes.

 

Mike