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2 October 2013 Last updated at 16:38 BST
The train driver was forced to apply the emergency brake when he saw the woman at Waterbeach on 12 September.
Richard Schofield, from Network Rail, said it was "one of the closest near misses we've seen".
British Transport Police is trying to trace the woman, who failed to stop despite the flashing lights and warning signals.
A cyclist came within seconds of death after failing to stop at a level crossing in Cambridgeshire.