A delayed yellow sequence is the result of a route with a reduced overlap set. The driver will approach a red signal which then clears as (s)he draws near. This enforced reduction in speed reduces the risk of SPAD -ing the next signal - the one with little or no overlap.
In Western Region E10k Route Relay Interlockings, the delayed yellow approach is selected automatically by the interlocking if the full overlap is unavailable for some reason.
Last edited by GeoffM on 15/09/2016 at 03:01