Sentence:  The colour-light signals admitting directly to the platforms and the inner <WSD>starters</WSD> (for short-length departures well up the platforms) are two-aspect, while those immediately beyond them are three-aspect, but elsewhere four-aspect signals have been installed in association with route indicators. 
Meaning of the word marked with <WSD> tags:  A railway signal controlling the starting of trains from a station or some other location, more fully called a starter signal or starting signal.