HOW GRADE TIME SIGNALS WORK


Two Shot Timer:
In appraoach to a grade time section of track, the train operator first sees the GT 20 sign (20 is the speed).
The next signal aspect is YELLOW over an illumunated "S" or "D" if there is a switch ahead set to the diverging route.
This begins a relay that is timed to clear after a specified duration for the formula:

...................................DISTANCE (to the signal)
.................TIME ..=...-------------------------------
.................................................SPEED


The signal will clear to proceed after the time expires and the next signal turns to Y/S. If not, the next signal remains RED and the train opeator has one more chance to slow the train to the specified speed.

The RESUME sign for the train length is located that number of cars past the end of the timed section.

As with automatic signals, a train on the regular control line cause the signal to display a STOP indication.

One Shot Timer (No diagram):
With one shot timers, usually in approach of the curve, the single signal will clear to yellow or green if the train takes enough time in the approach block. Again, the resume speed sign is at the train length beyond the end of the curve.


How Signals Work
How Grade Time Signals Work
How Station Time Signals Work

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- Joseph D. Korman - The JoeKorNer