Patrols at railway crime hotspots are being stepped up to try to prevent a traditional seasonal rise in problems.
Parents are being urged to warn their children about the dangers
Last year, Network Rail named a number of locations around the north-east of England as areas with high numbers of vandalism and trespassing incidents.
This year there will be high-visibility police presence at railway stations on Teesside and in County Durham from the end of this week.
Uniformed officers will be involved along with plain-clothes officers.
Sgt Alan Davidson, who is based at Darlington Railway Station, said: "We are going to have high-profile patrols round the Stockton, Billingham, Middlesbrough areas and Darlington.
Difficulty judging speed
"There will also be officers patrolling in plain clothes and unmarked vehicles."
Last year in the Middlesbrough area in July and August, there were nearly 70 vandalism offences, in Darlington 50 to 60 offences.
Sgt Davidson said trespassing was an ongoing problem on the railways and children saw older people doing it and copied them.
He said: "It's been proven that the younger element have far more difficulty judging the distance and the speed that the trains are travelling."
He said there were school visits to warn about the dangers and a national campaign and urged parents to warn their children about the dangers.