If 25,000 volts passes through a human body the result is not a pretty sight. You probably don’t want the gory details, but they are important - right down to the jokes. This is a story of death intended to save lives. First, black smoke comes out of your ears and nose. Then you start to shake, not because you’re practising a new dance routine, but because your blood is boiling. Then your clothes melt and stick to your skin. Finally, because humans are two-thirds water, you pop like an unpricked sausage in a microwave.

After that your remains are scraped into bags and buckets by people who hope they have learned to be tough. And someone has to tell your nearest and dearest that you won’t be coming home tonight because you got too close to the overhead power cables on a railway line.

John Roker, community safety officer for Railtrack Midlands, has warned thousands of schoolchildren of the grisly consequences of messing about on railways. Most of them remember his message, some of them word for word, for years. Mr Roker, also known as Uncle JR, has worked on the railways for 35 years, and has been doing his current job since 1994. A Londoner with the gift of the gab, he says Railtrack has its faults, but it does take safety seriously. And the people who are jeopardising the network’s safety are children.

Railtrack believes that 90 per cent of the 350 cases of railway crime reported every day - that’s one every 15 minutes - are committed by young people under 17. Five-year-olds have been caught putting objects on the track, while eight-year-olds have been seen playing “chicken” in front of high-speed trains.

A Railtrack survey in 1998 found that 30 per cent of 11 to 16-year-olds admitted to railway vandalism, and 20 per cent said they had taken short cuts along or across the track. While the survey was conducted in vandalism “hot-spots” - usually deprived urban areas - it indicates the scale of a problem the company says costs pound;30 million a year. And that’s not to mention the 11,500 hours of delay. Nor the 250 deaths of adults and children, the trauma of which spreads like ripples in blood, affecting families, train drivers, rail staff, police and schools.

In July this year, Kymberley Allcock, eight, and Sophie George, seven, were hit by a train while playing on the railway near Borth, Ceredigion. The two, who were out on a summer picnic with Sophie’s mother, her partner and three other children, were believed to have been dropping stones through a bridge to the river below. They were killed by a diesel train packed with holiday-makers.

Their deaths were, according to Huw Lewis, chairman of the council in the girls’ home village of Tre’r-ddol, “the worst tragedy that has ever hit us. The village is in a state of shock.” He says the railway line was unfenced and the area was popular with walkers.

And in August this year, a Liverpool Daily Post photographer snapped a gang of 30 children - some as young as eight - playing on the lines near Anfield. They laid their heads on the track to see if they could feel the vibrations of oncoming trains.

It is incidents such as these that Railtrack wants to prevent. Just before the summer holidays - the peak time for railway crime - it launched a safety awareness campaign aimed at the 22,000 schools on sites within two miles of a railway line. The substantial pack invites schools to become partners with Railtrack in its fight against crime. It links into the national curriculum and opens doors to resources on the web and on video. Aside from classroom activities, it contains graphic pictures of burned and scarred youngsters, and encourages schools to target parents with leaflets such as Where is Your Child?

The main thrust of the pack is information. And rightly so, says Gary Quigley, learning and support manager at the all-boys Woodlands school in Coventry, where Uncle JR is a regular visitor. Mr Quigley runs a successful personal and social education programme. He says the only way forward is to help children make informed choices. The just-say-no approach doesn’t work. “Kids won’t be bullied into believing things. All you can do is present them with facts so they can make informed choices. For example, John Roker won’t say ‘don’t play on the railways,’ but he will ask kids how they think they can get out of the way of tens of tonnes of metal hurtling towards them at 125mph.”

The power of peer pressure worries Gary Quigley and Railtrack. Mr Quigley calls it probably the biggest untapped pressure in education. “When kids go through their teenage years the approval of their peers is far more important than anything adults can offer. Many girls and lads are just not strong enough to stand up and say, ‘hey, I’m an individual. I do what I like’.” Pop star Britney Spears’s support for sexual abstinence is making it “cool” for teenage girls to say no to sex, says Gary Quigley. “Railtrack has to make vandalising the railways unattractive and not cool behaviour.”

The safety pack was put together with the help of Julia Shephard, a Swindon headteacher on secondment to Railtrack. She says simply warning young people they may die has little impact. “You need to personalise it. Youngsters who throw stones at trains see them as inanimate objects - they don’t think that the driver could be their mum or their dad, and they don’t think of the passengers as people they might be fond of. I hope our work in schools will help them learn to see the human issues.”

Despite years of ad hoc education, with each rail region running its own schools programme, trespass and vandalism are as big a problem as ever. This year, for example, Railtrack will spend pound;20m on fencing, even though “as soon as you put it up in some areas it is ripped down”, according to Sue Nelson of the company’s corporate affairs department.

Railtrack is looking for a culture shift, says Ms Nelson. “We are at the start of a very long road. We want to make vandalising the railways as unacceptable as drink-driving.”

So what is it about young people and railways? Is it the danger? The need for a secluded space? Or just the desire to cause trouble? Gary Quigley says there is an element of power and freedom in being able to wander around a railway, which, unlike a road, is not constantly in use. “And then of course, if you are that way inclined, there is the ability to do something disruptive.”

Julia Shephard talks of the excitement. “Some youngsters get an adrenalin rush from putting themselves in danger and there is a lot of peer pressure involved. And youngsters use the railways as a place to get away from adults - some anti-social activities, such as drug-taking, happen there.” In 1993 the battered body of two-year-old Jamie Bulger was left on a railway line.

The most obvious sign of railway vandalism is the “tagging”, graffiti that appears in staggeringly dangerous places - on embankment walls at the entrance to mainline London stations, for example. Aside from the risks children run “tagging” trains and trackside property, the graffiti cost millions to clean up and can obscure signs and safety messages.

Sue Nelson says the “golden age” of steam has lodged in the national psyche. People tend to regard railways with a nostalgia they would not dream of lavishing on the M1, for example. They find it difficult to see them as dangerous. “Thomas the Tank Engine has a lot to answer for,” she says.

Ignorance is a huge part of the problem. Young trespassers probably do not know, for example, that a third of the rail network is electrified - through overhead power lines or a “third” conductor rail. And they almost definitely would not know that you do not have to touch the cable or the third rail to be killed. High-voltage electricity can “jump” up to nine metres. Julia Shephard says children just do not understand the risks.

Mike Sutton, a former teacher who has worked on the railways for 25 years, agrees. Mr Sutton is Railtrack’s assurance manager in Swindon, and has been involved in a Home Office scheme to keep people under 17 out of court. Instead of meeting a magistrate, they meet the people they have offended against. About once a fortnight, representing Railtrack, he gets to chat with a young person who has trespassed on or vandalised the railways. He remembers two teenagers who broke a glass signal lens. When they were told they had disrupted trains for hours and could have caused an accident involving hundreds of people they burst into tears. They hadn’t realised, they said. They thought it was just a two quid bit of glass.

In reparation the pair were asked to spend 12 weeks weeding the school playgrounds. At the end of the 12 weeks they asked if they could do some more. Mike Sutton says there are no bad children, just ones who suffer from a lack of self-esteem and whose parenting leaves a lot to be desired. “While we cannot tolerate what they do, I am left feeling that there are no out-and-out evil people, just bored ones.” He is pleased that Railtrack has “decided to stop moaning and dismissing it all as ‘society’s’ problem”. He says: “If we didn’t do something we would all still be shaking our heads in 10 years’ time. We now have a 10-year strategy to educate the up-and-coming generation.”

One member of that generation has already been won over. John Roker was called in to talk to eight-year-old pupils in a Milton Keynes primary, some of whom had been trespassing on the railway. The head said he would prefer frightened kids to dead ones. So Mr Roker showed the children pictures he would usually save for teenagers. “There were a few white faces, but no one blubbed - until afterwards. A teacher brought along a little boy crying so hard the tears were almost coming out his ears. He said he hadn’t realised about the electricity.”

For a free copy of the Railtrack safety pack contact Graphic Ad, 0113 2786579.