Origins of Elizabeth S-Curve?

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Thirdrail7

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The speed limits for the outer tracks (1 and 4) remained 55mph with no change, but with ACSES the code drop to 45 was probably removed. I am not sure. Thirdrail can probably give more upto date info on that.

Jis, the cab signal drop was indeed dropped. If one goes through the curve today it is indeed much quicker then before. This is one area where PTC has actually benefited things.
The cab signal codes were not dropped. Even if they were dropped, the actual distant signals approaching the area going west on 1, 2 and 3 track can't display a clear since it doesn't have a clear aspect. Neither can the automatic signal on 4 track at the same location. However, the distant signal is capable but you're already down to 45mph. Going east, the distant signals on A and 1 can't display a clear aspect while track 4 and B aren't signaled east. 2&3 track east are capable of displaying clears which is why it isn't likely see the cab drop go away until they change the signal system completely. This is because they want certain locations protected in case there is ACSES failure.

There was a plan to change the signals so you could receive a Cab Speed 80. However, since you'd have to physically change the signal bridge, it is unlikely to occur until the convert the territory to 562 (which is slowly occurring.)
 

jis

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Thirdrail. Thanks for the clarification.

So effectively at what speed can the Acelas go through those two curves today? I suppose they can accelerate as fast as possible after meeting the signal restriction on the segment protected by the signal? I guess I am still a bit confused.
 

Thirdrail7

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Thirdrail. Thanks for the clarification.

So effectively at what speed can the Acelas go through those two curves today? I suppose they can accelerate as fast as possible after meeting the signal restriction on the segment protected by the signal? I guess I am still a bit confused.
You're not confused Jis. You hit the nail on the head. They cab signal drop approaching Elmora is on a timer. An acela will suffer the forced compliance of reducing speed to avoid the penalty. It will knock you down to roughly 60mph going east and 45 mph going west (since the track speed is lower). As soon as it releases you may accelerate and you will hit toe curves at track speed.
 

Thirdrail7

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The timer starts when you pass the signal's impedance bond. You needn't pass another signal or impedance bond for the upgrade. I believe they are set for twelve seconds. At any rate, after the 12 seconds, the cab signal indication will allow for a greater speed...assuming there is nothing ahead. This is beneficial since it releases regardless of speed.
 

Touchdowntom9

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The cab signal codes were not dropped. Even if they were dropped, the actual distant signals approaching the area going west on 1, 2 and 3 track can't display a clear since it doesn't have a clear aspect. Neither can the automatic signal on 4 track at the same location. However, the distant signal is capable but you're already down to 45mph. Going east, the distant signals on A and 1 can't display a clear aspect while track 4 and B aren't signaled east. 2&3 track east are capable of displaying clears which is why it isn't likely see the cab drop go away until they change the signal system completely. This is because they want certain locations protected in case there is ACSES failure.

There was a plan to change the signals so you could receive a Cab Speed 80. However, since you'd have to physically change the signal bridge, it is unlikely to occur until the convert the territory to 562 (which is slowly occurring.)
Sorry for digging up a very old thread, but is this still the way in which the signally is done in 2022 even with full PTC implemented? Or has it been made to be 80mph cab signal for the express tracks as you mentioned it might be? Lastly, what is 562?
 

jis

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Sorry for digging up a very old thread, but is this still the way in which the signally is done in 2022 even with full PTC implemented? Or has it been made to be 80mph cab signal for the express tracks as you mentioned it might be? Lastly, what is 562?
The area has been converted to 562, and civil speed limit is now specified through ACSES transponders and not via track circuit speed code hackery. That is how speed limit for Class A trains (Acela with tilt enabled) is enforced at IIRC 80mph on tracks 2 and 3.

Rule 562 is the NORAC Rule that applies to operation on territory where Cab Signals are used without fixed Automatic Block Signals. In case you are interested in the gory details which spans several pages of printed material take a look at, for example - NORAC Operating Rules Tenth Edition (big PDF file) page 114.
 

dlerach

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I believe that the southern portion of the curve is 2° (3000 ft), which is sharper than the northern portion. While that's not sharp for most of the United States, for the NEC that's pretty sharp. With 6" superelevation an Amfleet should be able to traverse the curve at about 88 mph. As Anderson remarked, though, it's not so much the degree of curvature; it's that two curves in opposite directions are stacked on top of each other. Because there's no spiral between the curves, there's very little potential for superelevation, and thus the brutally low speed limit emerges. With no superelevation, an Amfleet should be allowed something like 55-60, which, surprise surprise, is not far from the actual speed limit.
 

Touchdowntom9

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I took the Acela last week outside of rush hour so not too much traffic. We entered the curve at about 50mph but hit close to 75/80 as we were in the middle of it. Seemed odd as I wasn’t sure why we would dip from 100 to 50 just to accelerate again in the middle of the curve
 
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