The number of people trespassing on railway lines in Wales has hit a five-year high, according to Network Rail and British Transport Police.
Last year there were 524 separate incidents where people risked their lives on the rail network in Wales and the borders - up 2% from 2015.
The figures show a spike in incidents during the school holidays at Easter and summer time.
British Transport Police (BTP) said it was dealing with incidents every day.
According to the data, one person every hour trespasses on the UK's rail network.
Ch Insp Mark Cleland, from BTP in Wales, said: "We believe the number of children we encounter trespassing every year is sadly just the tip of the iceberg.
"Every single day we are called to the tracks because a train driver has had to sound their horn or apply their emergency brake in a desperate bid to avoid youths on the line, who then run off, seemingly unaware of the danger they have put themselves in.
"We continue to do all we can to keep youngsters safe by patrolling areas where we know they're likely to trespass and prevent them from doing so.
"However, we cover thousands of miles of track and we cannot tackle this issue alone.
"It's not a game. They are real tracks, with real trains and real-life consequences."
'Dangers not obvious'
In 2016, 14 children were caught trespassing by police in Wales, with boys between 14 to 16 the most frequent offenders.
With the Easter holidays in full swing, Network Rail is concerned there could be another increase this month.
Andy Thomas, route managing director for Network Rail Wales, said: "Every April we see a huge rise in the number of people taking a risk on the rail network and it's worrying that these numbers seem to be going up. Britain has the safest railway in Europe but still too many people lose their lives on the tracks.
"The dangers may not always be obvious but trains can travel at high-speeds, so even if they see you, they can't stop in time.
"It may seem harmless to take a shortcut, or fun to play on the tracks, but this is not only illegal, it is also very dangerous. Taking a short cut or messing around on the tracks can result in serious life-changing injuries or death."