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Approach Control

Approach Control

Approach control is where a signal , with a route set for a diverging line with a lower speed limit than the 'straight ahead' line, is held at a restrictive aspect until a train approaches it. The signal is usually held at red, but occasionally approach control from yellow may be seen. The purpose is to ensure that the driver has slowed sufficiently for the diverging route; if the signal wasn't approach controlled, the driver would only know that they were taking the slower route when the junction signal came into view- too late to reduce speed. The size of the speed difference between the two routes governs the time at which the signal clears; sometimes it may be immediately after the train passes the previous signal, in other locations there may be an additional delay.

At locations where the diverging speed is relatively high, and approach control from red would cause an excessive reduction in speed, Flashing Yellows are used to provide warning of the diverging route.

Crucially, the driver must never expect the signal to clear to a proceed aspect, and failing to heed this has resulted in numerous SPADs .

Illustrated examples of approach control, with further detail, are available in Clive Feather's article on approach control.

Last edited by Steamer on 27/11/2017 at 17:15