Train carriages were taken out of service this week after vandals sprayed them with graffiti while they were in the Horsham railway sidings.
On Sunday night (February 8) two coaches were attacked while they sat in the sidings in Parsonage Road. British Transport Police are investigating.
A spokesman for BTP said: “It can be dangerous not only for the individuals causing the damage. It’s incredibly dangerous and they are risking their own lives doing it as well as those of others.
“It serves no purpose, it costs to repair and the network was affected on Monday. It’s illegal because it’s criminal damage, but also for trespass.”
If anyone has any information about the incident call British Transport Police on 0800 405 040 or text 61016 quoting ref 511 of 8/2/15. People can also call Crimestoppers anonymously on 0800 555 111.
The vandalism in Horsham was one of three sites the Southern Railway network targeted at the weekend.
A Southern Railway spokesman said: “Thirty-four carriages in total were struck by graffiti vandals over the weekend at three of our berthing sites – Stewarts Lane (Battersea) Horsham and East Grinstead.
“Graffiti was discovered at Stewarts Lane at 9.30 on Sunday morning, At East Grinstead at 5.40 on Sunday morning and at Horsham at 11.30 Sunday night.
“We don’t send vandalised trains into service, so unfortunately we ended up having to cancel 15 trains on Monday as a result. All of the carriages have had the graffiti removed and are back in service.”