I'm quite intrigued by your timer system in your signalling. Other than CBTC, the subway uses fixed block signalling right? Well dont the trains receive speed codes for the TOs to follow rather than use timers to regulate speed? But I heard the trains here dont have in-cab signalling. Or are timers some additional safety feature to the signalling system exclusive to NYC subway only? When are where were they first implemented? I wonder if my perception of how timers work are correct:
TOs know that they going to pass a timer once they see a GT or ST sign and thus slow down to the speed as printed on the sign. There are timers that give u 1 chance or 2 chances to clear. Its about presetting the signal to show a clear aspect after a fixed amt of time from the point a train is detected in a block. The time given is pre-determined by how long a train takes go pass a certain section at a certain speed and that if they reach the signals faster than the preset time the signal assumes the train is going too fast and makes it trip the arm to stop it. But do engineers add a few seconds more to this preset time to cater to small allowances in train speed or that whatever they calculate before hand is just set as accordingly? Does anyone in here know the exact time preset for all the timers across the subway? Typically, How much time is given?
So a 'stopwatch' in the signal starts once a train enters a traffic block and after the preset time, the trip arm retracts and the signal turns green and the S disappears. For one shot timer, its only one try to clear while for two shot timer, the first barrier wont have a trip arm but will have a signal to let TO know if they have cleared the first timer then the second signal will have both trip arm and signal ready to trip a train if its going too fast.
For station timers, its basically to allow the back train to inch up to the front one at a station so long as its under the GT speed prescribed. If the train is inching to the front one too fast, the signal just before the platform will trip it before any collision?
When I was in NYC last June, i wasnt able to notice a timer. All the signals looked the same to me. Is one characteristic of a timer include having the S light at the bottom? What other characteristics are there to tell from a normal signal and timer signal? Are timers compatible on CBTC-ed lines?
For wheel detectors, are they supposed to work in hand with timers? Basically the driver must slow down to the prescribed speed before passing the signal that has the WD light if not he will be tripped. Again, is this something thats exclusive to the subways? When and where were they first implemented?
I know there's a guide on this on nycsubway.org but i still dont quite understand how it works after reading it multiple. So, hope i can clarify my doubts here![:)]()
TOs know that they going to pass a timer once they see a GT or ST sign and thus slow down to the speed as printed on the sign. There are timers that give u 1 chance or 2 chances to clear. Its about presetting the signal to show a clear aspect after a fixed amt of time from the point a train is detected in a block. The time given is pre-determined by how long a train takes go pass a certain section at a certain speed and that if they reach the signals faster than the preset time the signal assumes the train is going too fast and makes it trip the arm to stop it. But do engineers add a few seconds more to this preset time to cater to small allowances in train speed or that whatever they calculate before hand is just set as accordingly? Does anyone in here know the exact time preset for all the timers across the subway? Typically, How much time is given?
So a 'stopwatch' in the signal starts once a train enters a traffic block and after the preset time, the trip arm retracts and the signal turns green and the S disappears. For one shot timer, its only one try to clear while for two shot timer, the first barrier wont have a trip arm but will have a signal to let TO know if they have cleared the first timer then the second signal will have both trip arm and signal ready to trip a train if its going too fast.
For station timers, its basically to allow the back train to inch up to the front one at a station so long as its under the GT speed prescribed. If the train is inching to the front one too fast, the signal just before the platform will trip it before any collision?
When I was in NYC last June, i wasnt able to notice a timer. All the signals looked the same to me. Is one characteristic of a timer include having the S light at the bottom? What other characteristics are there to tell from a normal signal and timer signal? Are timers compatible on CBTC-ed lines?
For wheel detectors, are they supposed to work in hand with timers? Basically the driver must slow down to the prescribed speed before passing the signal that has the WD light if not he will be tripped. Again, is this something thats exclusive to the subways? When and where were they first implemented?
I know there's a guide on this on nycsubway.org but i still dont quite understand how it works after reading it multiple. So, hope i can clarify my doubts here
