Sentence:  The collision occurred when an up empty electric train travelling on the up main through line <WSD>overran</WSD> the inner home signal and rammed the side of the departing 6.14 p.m. Waterloo-Weymouth steam train, which was leaving platform 12 for the down main through line. 
Meaning of the word marked with <WSD> tags:  To run past; to run beyond.