A train windscreen was smashed when a brick was hurled from a station bridge at Goldthorpe.
Three youths were seen standing on the bridge at the time of the attack.
Now British Transport Police (BTP) officers are appealing for information about what happened on July 29.
PC Sandra Murray, the investigating officer said: “The 15.25 Plymouth to Leeds service was approaching Goldthorpe station at about 6.30pm when a brick was thrown at the windscreen from a bridge.
"Three youths were seen standing on the station bridge, one of whom threw the brick at the train. The windscreen was damaged as a result, but fortunately neither the driver or passengers were injured."
BTP say they are keen to find those responsible as officers are concerned the youths do not realise the dangers of throwing objects at moving trains.
Officers want to trace three boys seen standing on the station bridge at the time, aged between 13 and 15, one of whom was wearing a red chequered top.
PC Murray added: “Fortunately on this occasion, no one was injured as a result, however the consequences could have been far worse."
"This was an extremely foolish and dangerous act, which put the driver and passengers on the train in danger.
“Patrols have now been stepped up in the area to catch and deter any vandals from carrying out this type of extremely dangerous crime.”
Anyone with information is asked to contact British Transport Police by calling 0800 40 50 40 or texting 61016 quoting B8/NEA of 06/08/2013. Alternatively, call Crimestoppers on 0800 555 111.
