Four "reckless" youths who tied a metal ladder to railway tracks in West Lothian are being hunted by police.
Officers said the consequences could have been "catastrophic" when an Edinburgh train ploughed through it at Livingston North station.
The Scotrail driver spotted the ladder and applied the brakes, but was unable to stop in time.
The youths were witnessed tethering the ladder to the tracks.
They remained at the scene to watch as it was hit by the train.
British Transport Police tweeted an image of the crushed ladder in a bid to trace those behind the incident which happened earlier this month.
PC Craig Wilson said: "The ladder could have easily been propelled onto the platform and struck a member of the public. Not to mention the fact that this train could have been derailed.
"It might have seemed like fun but the consequences could have been catastrophic."