Vandals have thrown a child's scooter at a ScotRail train, causing widespread disruption for several hours.
The metal toy was dropped from a bridge and hit the train's pantograph, which connects it to overhead power lines, leaving debris over the wires.
Services between Edinburgh and Glasgow via Bathgate were halted after the attack at Airdrie in North Lanarkshire.
The incident just before 6pm yesterday forced the cancellation or delay of trains for around two-and-a-half hours.
An investigation has been launched by British Transport Police (BTP).
A rail source said: "It's lucky that whoever threw that did not get an electric shock from the overhead wires.
"The safe working distance from the overheads is 9ft as the 25,000 volts can jump that distance and is attracted to metal items."
A spokeswoman for the ScotRail Alliance, which includes track owner Network Rail, said today: "This appears to have been an act of mindless vandalism.
"We will do all we can to assist BTP to catch the perpetrators.
"A ScotRail train, not in passenger service, was vandalised around 6pm yesterday evening near Airdrie, when a scooter was thrown onto its roof, striking the pantograph and depositing debris on the overhead lines.
"The line was blocked for a time to allow teams to remove the scooter and for the train to be moved.
"Services heading west to Milngavie and Helensburgh had to terminate at Bathgate, with buses replacing trains.
"At the other end of the line buses were also running between Helensburgh Central and Dumbarton Central."
Trains began returning to normal around 8:30pm.
BTP said the incident had caused "widespread disruption" to the network.
A spokeswoman said: "At around 5.50pm, BTP officers were called to the over bridge at Gartlea Road and upon arrival with Network Rail they retrieved a large children’s scooter from the top of a train that had stopped there.
"It is thought that the scooter was thrown by someone who was on the bridge.
"Officers would like to speak to anyone who may have seen people acting out of the ordinary or loitering in the Gartlea Road area, adjacent to Halfords and Morrisons petrol station around the time of the incident."
Investigating officer Constable Mark Harrigan, said: “This was a particularly alarming incident for the driver of the service in question and in particular was a great inconvenience to the wider public who were subjected to lengthy delays and cancelled services as a result of this reckless act of vandalism.
“Fortunately no one was hurt, but trespassing on the railway or risking coming into contact with overhead wires is incredibly dangerous. Criminal damage to the railway can result in serious and even fatal consequences for rail passengers, workers and those committing the damage."
BTP said anyone with information should call 0800 405040 or text 61016, quoting reference number 377 of 5/1/17.