British Transport Police investigating a malicious obstruction at Wivelsfield railway station have released CCTV images of a girl they wish to speak to.
A group of girls, believed to be aged in their teens, were on the platform at the railway station.
One of the girls grabbed hold of a bicycle and threw it onto the tracks, said police.
The incident happened at 6.50pm on November 14.
An approaching train then struck the bike at speed and the bike was dragged down the tracks, added police.
A BTP spokesman said: “The mindless act of vandalism could have ended in far more serious consequences.
“Thankfully no one was injured during this incident.
“There was significant disruption to the service as repairs were made and the bike untangled from the train.”
Anyone with information should get in touch by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 544 of 14/11/2017.
Alternatively, people can contact Crimestoppers anonymously on 0800 555 111.