vasim said:
Whilst pulling a signal off slowly is not in the method of working, a driver knows what the signaller means. You can't do that with an electric signal anyway, semaphore or colour light.
The rule book says to only clear the signal when the train is at, or nearly at, a stand at the signal. With colour lights you use the nearly at a stand to keep them rolling while they used the slowly pulling off with semaphores as a message to the driver that it was caution rather than I forgot you. The nearly at a stand still applied with the semaphore. The semaphore just allows a bit more communication to the driver.
We sometimes stop freights using the diversionary loop at Laverstock on the slight downgrade on a red to allow the train in the section ahead to get to the top of the bank. Starting the train off on a yellow means he trundles round the loop and gets a rolling start at the bank on the other side rather than getting stopped again at the bottom of the bank. Word of mouth between the drivers lets them know what we are doing and prevents working the loco so hard up the bank from a standing start. It does make a huge difference to the speed up the bank starting at 20 rather than 0.