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'89 Liberty MCI

Switches and Junctions Questions

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1. After a Manhattan-bound (5) clears the local track at Rogers junction, how much time must pass before a (3) at Nostrand Avenue can get the green signal to go through the junction?

 

2. After a (3) clears the track, how much time must pass before the (5) can get the green at President?

 

3. After a (2) clears 142 Street junction on its way out of the Bronx, how much time must pass before a northbound (3) can get the green at 135 Street [or the closest the (3) can be to 142 Street junction while waiting for the (2) to clear the tracks]?

 

4. After a train pulls out from, say, the west pocket track at Flatbush/Nostrand Aves, how much time must pass before an impending train can get the green signal to enter the west pocket track?

 

5. Assuming the east pocket track is clear and a train is pulling out from the west track, how much time must pass before the impending train can get the green signal to enter the east pocket track?

 

It seems like it should be a little less since the Tw/Os do not have to wait for the train pulling out from the west track to clear the switches that the impending train needs in order to enter the east track. In that situation the switches needed to direct the impending train to the east track can be set before or while the departing train is on its way out; the impending train just has to wait for the departing train to clear the crossover in order to get the green signal.

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It's not that the signal is "green", it's that the signal is "not red".

 

There are several reasons why a a signal would display a non-restricting aspect, the absence of a train in block is only one of them.

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It's not really about time, it's about trains occupying the same section of track-the section of track between two signals must not be occupied by a train, this is called an Absolute Block.

 

If two trains occupy the same signal block then the trains are not protected from hitting one another because the signal system's circuit isn't opened to present an electrical 'space' allowing signals to turn red and stop arms to come up.

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I meant "non-red" rather than "green." Forgot for a second that in several cases the signals will only be yellow or whatever.

 

I am essentially trying to figure out how many trains per hour that small section of both the westbound and eastbound local tracks shared by the (2)(3)(5) at Rogers JCT currently handle and have the ability to handle based on how quickly the switches can move and the lengths of the signal blocks before each section of track.

 

I also wish to know the minimum interval between the time a train begins pulling out from a pocket track at Flatbush and the time you can have another train parked on that same pocket track (after the first one leaves of course). And the minimum interval between the time a train beings pulling out from the west track and the time you can have another train parked on the east track. Of course a simultaneous east track pull-out and west track pull-in is no issue since trains do not conflict in that case.

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Go down there with a stopwatch and find out yourself. :cool:

 

Tw/O's no longer control the IRT, its all computer.

 

But honestly, that will be the best way to answer all of these and other questions about Nostrand trunk service you may have.

Edited by TwoTimer

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Nothing quite as scary as flying into Franklin Avenue northbound on a (3) or late (4) and "watching ATS kick in..."

 

Well there was that time I almost hit that second homeball coming into 135th Street around the S curve... talk about shaken! :lock:

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