Signal Question

[B3 Via Av U]

I noticed that on the 6th Avenue side of the Manhattan Bridge, there is a signal with a bunch of numbers on it right on the tunnel portal on the N/B side.

 

 

What is this signal supposed to be? All answers are appreciated.

 

 

Perhaps TwoTimer can answer this.

 

Thanks!

[Threxx]

I noticed that on the 6th Avenue side of the Manhattan Bridge, there is a signal with a bunch of numbers on it right on the tunnel portal on the N/B side.

 

 

What is this signal supposed to be? All answers are appreciated.

 

 

Perhaps TwoTimer can answer this.

 

Thanks!

 

 

A signal to direct the flow of trains onto 6th, probably.

[mark1447]

The numbers are Speed restrictions. 20 is common around the system, which means the train has to be at or below 20 MPH when passing the signal or the train will "trip" (aka go into EM Brakes) along the way.

 

Learn more about Signals:

 

http://www.nycsubway.org/articles/signals.html

[TwoTimer]

I guess I was summoned...

The numbers are Speed restrictions. 20 is common around the system, which means the train has to be at or below 20 MPH when passing the signal or the train will "trip" (aka go into EM Brakes) along the way.

 

Learn more about Signals:

 

http://www.nycsubway...es/signals.html

Buzzzzzzzzzzzzzzz. For one, timers are timing the amount of time the train is in that particular block, calibrated to clear the next one (or the one leaving the block on one-shots) based on a given speed which equals that amount of time.

 

He is probably talking about the pair of signals close together near the portal. The first one is a repeater, which just mimics the signal right behind it. It has a REP plate on it (with the numbers). It was installed because the one behind the pole is almost invisible until a train is almost on top of it. It has no train stopping ability, which the website doesn't say (no stop arm on a repeater, EVER). Also, the speed limit on top of the bridge and coming down is 25, under grade time (assuming you read the whole section on signals). It is safe to do 21-24mph on the bridge, depending on the spot. There is no GT25 sign near the portal. And also, 20 is sorta common but its not THAT common. Training tells you to be 5-7mph below the posted speed, since most timers are incorrectly calibrated. Experience alone dictates what one can do at any given timed signal, sometimes that, sometimes even slower, a handful of times more. A few popular spots...

 

20mph - Broadway Bridge , not timer enforced. Williamsburg bridge has timers, which indeed clear at 20.

25mph - Manhattan Bridge on the span itself, with the exception of a couple they clear at 21-25 depending on the signal. There's one on the n/b Broadway side on the span that only clears at 19. Most train operators just keep it at 20 and clear everything nicely.

25mph - North Channel Bridge . Its typical to enter the block higher than this, then brake it down, clearing this one shot at 10-15, then powering up down the other side.

20mph - South Channel Bridge . Clears much lower than 20.

[Fan Railer]

Random question, but if you run a yellow timer signal before it clears to green, will the following red signal operate normally and clear to yellow? or does this situation count as running the timer and therefore will result in the red signal not clearing?

 

Only asking bc it seems like standard operating protocol to allow the yellow signal to clear to green before proceeding forward.

[Kamen Rider]

one would think that clearing the timer properly would take precident. however anything could happen as this is the MTA we're talking about, and "thinking" is not a requirment to get a job there.

[TwoTimer]

Ok ill do a crude diagram for you.

 

X__________[GT25]O__________O__________O__________O

 

Train is at point X... moving along at 25mph. Passes GT25 sign and continues along at 25. Assume all signals are calibrated correctly. When train gets to the yellow one, it will turn green, the one following will turn to O. Process repeats itself until the head of the train leaves the timed area. Assuming no other speed restrictions or station, wrap it back up.

 

If train comes at said signal at 20mph, the yellow one will go green at a distance in front of him. If train comes at said signal at 30mph, he will pass the O with the following one still red. Assuming the train slowed down (well below 25mph) for the red, it will clear to green (both signal blocks timers met simultaneously).

 

Now lets put the time factor into the equation.

 

Train comes at the GT sign at 30. Train slows down to 20 by time it reaches the O. The next signal will clear, as the amount of time the train spent in the block is equal to as if it was going 25 the whole time. T/O's that know all the signals are calibrated correctly won't "challenge" that first one, as that only loses a teeny amount of time (after braking it back down, ur going 20 when u should have been going 25).

 

Now lets hit that first red.

 

All the blocks are evenly spaced out, it takes 5 secs to go from block to block at 25. Train passes GT25 at 50mph. Goes past the O (the following signal remains red of course). Hits the next signal. Enough time didn't pass for the first one to clear.

[B3 Via Av U]

I rode the on my way to Herald Sqaure yesterday and figured out what you (TwoTimer) meant about the double signals at the portal. Thanks!