Kids have been risking their lives by crossing live railway tracks, leading to a stark warning ahead of the half-term holidays that it is "extremely dangerous".
Rail bosses said trespassers were putting their lives and others at risk with a rise in cases - noted especially in Gloucester and Bristol.
Network Rail and British Transport Police (BTP) said that people should not go on the tracks and that they are not "a playground".
More than 250 people have risked their lives since the start of April by trespassing on the railway which runs from Paddington to Penzance, as well as through Bristol and Gloucestershire.
The majority of these incidents have been reported around Gloucester, Stroud, Moreton-in-Marsh, and in and around Bristol, especially near stations and level crossings.
Many of the reports have involved children and young people. Several incidents of people walking on the tracks in these areas have been reported to BTP, including incidents involving a group of young people crossing the live track at Moreton-in-Marsh station last week.
Several measures have been put in place to tackle the issue, including additional signage, installing cameras, and hosting educational events. As well as the risk of being struck by a train, electrification on parts of the route add further danger, as 25,000 volts of electricity can jump from overhead lines.
Fast moving trains, slippery lineside conditions and unsteady ground combine to create a serious risk, reported BristolLive.
Andy Phillips, Network Rail programme manager for route crime, said: “Incidents of trespass on the railway cause issues for everyone using the network, where an individual could sustain life-changing injuries and in the worst-case scenario, loss of life.
"The railway is not a playground and what they are doing is extremely dangerous. It is disappointing to see people blatantly disregarding their own and others’ safety.
"We urge parents, teachers and other adults in responsible positions to ensure children understand the risks of trespassing, as well as encouraging the public to report any trespass incidents they witness via the BTP text service on 61016."
Embedded Inspector Dan Collins Young from British Transport Police said: “We see hundreds of people taking risks on and around the railway every year, resulting in tragic consequences or life-changing injuries. Both outcomes are avoidable.
“People should never anticipate when the next train is due – particularly as train services can run at any time of day or night and travel at high speed.
"Our network of uniformed and plain-clothed police officers, and over 150,000 CCTV cameras, monitor the railway 24/7 – we will actively pursue and take positive action against those who fail to comply with the simple instruction not to trespass.”
Trespassing is illegal, and people doing so could face a fine of up to £1,000, as well as being left with a criminal record. Anyone who spots someone trespassing is asked to contact BTP by texting 61016 or calling 0800 40 50 40. Always ring 999 in an emergency.
BTP and Network Rail run a hard-hitting safety campaign, You Vs Train, which highlights the devastating consequences that trespassing on the railway can have.
