British Transport Police is seeking a man who was caught on CCTV risking his life by crossing railway tracks to catch a train at Crosskeys station near Newport, Wales.
A video of the incident has been released in an effort to identify the trespasser.
The incident took place at 8pm on Wednesday 15 May and saw the man jumping across the opposite platform, walking across the tracks and around the front of the train onto the other platform.
He then tried to open the doors to the train but failed to do so as the train moved away.
In a statement, Inspector Mike Jones, officer in charge at British Transport Police Cardiff, said: "I am genuinely appalled to see that, despite our constant warnings, some people are still willing to risk their lives by trespassing on the tracks.
"This shocking footage clearly shows the man pass around the front of the train, in the direction it is about to move, to try and get on board.
"I am absolutely dismayed to see people are willing to risk their lives for the sake of a few seconds rather than waiting for the next train. It is utter stupidity."
Inspector Jones added: "I cannot emphasise enough the dangers associated with this type of stupid behaviour. It is simply not worth it.
British Transport Police has asked anyone with information to contact 0800 40 50 40 quoting reference B7/WA of 30/05/2013.
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