NYC Subway Mid-Station Signals

From what I remember when I was a regular NYC subway rider and what I see on current videos, there usually are signals mid-platform at some/all stations which are amber (or red). I am curious as to why these signals are in use. The operator knows that the end of the platform approaches, and the signal beyond the end of the platform usually is green or amber. What is the purpose of these signals

Station timers are mainly to make sure the train operator approaches and enters the station at an appropriate speed.

In the case of Canal St on the A,C,E for example- there are switches at the end of the platform and of there is a train crossing over it is to protect that train. Even if the signals at the end of the platform are clear, the mid platform signals are still active.

Another example is if the station is on a downward grade, it is to make sure the train stops properly.

There are other reasons which others will post (the ones above are the only ones I can think of at the moment).

Would they be able to allow 2 trains in a station at the same time? I know Jamaica LIRR prior to COVID, I'd sometimes see 1 train entering the single "transfer" tracks that each side has where the doors open on each side while another train was still leaving the station.

gprimr1 wrote: ↑Sun Nov 07, 2021 11:37 pm Would they be able to allow 2 trains in a station at the same time? I know Jamaica LIRR prior to COVID, I'd sometimes see 1 train entering the single "transfer" tracks that each side has where the doors open on each side while another train was still leaving the station.

In the case of Canal St I think one train would have to 'key by' the station timer signals (with permission, of course) if the other train is leaving the station.

A similar situation is 145 St on the B, D when the B terminates in the middle during the day and has to cross over to the local track when leaving the station. In that case an approaching downtown D is actually stopped mid platform until the B has cleared the switch.

I had always assumed that having two short blocks would speed service in areas (like stations) where speed is slow. There is no need for the outgoing train to completely vacate the station before the subsequent train starts to enter. There will always be a red signal between the two trains. When the last car of a departing train passes the mid-station signal, the following train can start to enter the station. By the time the second trains gets to the mid-station signal, the first train will have completely vacated the entire station and the mid-station signal can go to yellow.

In the NYC subway system the basic rule is to have two red signals between each train. The exception to that is if supervision gives the following train permission to close in on it's leader because of an emergency situation where the first consist cannot completely clear the station. It's a safety precaution.

In "classic" NYC Board of Transportation signal design, the signals 1/4-way in from the station entrance and 1/2-way in are there for headway performance, to get the next train into the station as close behind the leading train as can be done safely. There is usually an insulated joint without a signal 3/4-way in under those circumstances.

This is very typical in close headway situations like the trunk lines in manhattan. Towards the outer ends of the lines away from manhattan, less common - headway performance is less demanding.

DaveBarraza wrote:In "classic" NYC Board of Transportation signal design, the signals 1/4-way in from the station entrance and 1/2-way in are there for headway performance, to get the next train into the station as close behind the leading train as can be done safely. There is usually an insulated joint without a signal 3/4-way in under those circumstances.

This is very typical in close headway situations like the trunk lines in manhattan. Towards the outer ends of the lines away from manhattan, less common - headway performance is less demanding.

It seems to me that the rationale for mid-station signals is primarily that adding blocks will have effects on signals prior to the station, thus helping to keep the upstream blocks moving by giving more green or yellow signals.

Once a departing train clears the mid station signal then the signal at the station entrance can be approach allowing following train to access station faster. Next preceding signal can then be green. Without mid signal following train has to wait until leading train completely clears station for following train to get a yellow at station entrance. Proceeding signal anywhere from 500 - 1500 feet from station can get a green instead of yellow.