A car rolled from a car park and through a wooden fence, hitting a train pulling out of a busy commuter station at the start of the morning rush hour.
The car hit a semi-fast train to London King's Cross
The accident happened at Royston station in Herts when the parked car rolled back onto the platform.
It collided with the back of a First Capital Connect train to London King's Cross as it pulled out of the station.
No-one waiting on the platform was hit by the car and the carriage was only "slightly scuffed" in the collision.
Waiting commuters and an off-duty railway worker pushed the vehicle back into the car park, said a spokesman for First Capital Connect.
The fire brigade and British Transport Police were called to the accident, which happened at 0652 BST.
The driver of the train was unaware it had been hit until contacted by train staff.
The train was examined at the next station.
The spokesman added: "Clearly had this happened just before the train arrived at the station it could have been a serious incident."
The wooden fence at the station is due to be replaced with a metal structure, but temporary repair work has been arranged to make it safe in the meantime.