A security guard who witnessed the violence said it was lucky no-one was killed.
The guard on duty at the closed concrete-paving plant Marshalls next to the station helped police pull teenagers away from the level crossing as the gates came down for a high-speed train to come through.
Police used spray and had their batons drawn to break up trouble-makers who were clashing on the level crossing at Nutbourne train station, in Broad Road on Friday, September 18.
Lucky to be alive
The G4S employee, who did not want to be named, said: "There were about 300 teenagers in the car park and on the station.
"A lot of the trains that go through don't stop '“ I'm surprised there wasn't a fatality.
"I was trying to stop people, from going on to the track, and then the gates came down and we had to quickly grab people '“ it was quite scary."
The fights broke out between teenagers from Leigh Park in Havant, and Chichester, who began shouting at each other from one side of the station to the other.
They then met on the crossing as the train gates came down.
The security guard said the teenagers descended on the village for a party in a field behind the Marshalls site, organised on social networking website Facebook.
He said teenagers as young as 13 travelled from Portsmouth, Worthing, Bognor Regis and the surrounding areas for the night.
Only two 13-year-old girls remained until the morning after staying in the field in sleeping bags.
He added: "It's different with adults, when there might be a row, but with kids they all group together and if it kicks off they all join in.
"But it could have been a lot worse.
"If it had gone on until the early hours of the morning the kids would not have had any way to get home.
"They were told there were going to be music tents and alcohol. There was lots of alcohol, but there was one bloke with a small amp."
Residents in the area said they think the youngsters had a trial run for the party two weeks ago when a group went to the same field for the night.
Chidham and Hambrook Parish Council vice-chairman Steve Clark said it was an unusual thing to happen in the area.
"I have lived here for 20 year and it's the first thing that has happened in my time," he said.
"Let's hope it's a one-off and the police will keep an eye on it.
"If things get a bit out of hand, like a ball being kicked against a house, that's okay, but this is obviously a bit more than that."
A Network Rail spokesman said: "This is completely reckless behaviour.
"Not only do you have 200-tonne trains travelling at anything up
to 80mph, there is 750 volts of electricity running through the third rail.
"Both of these could easily have seriously injured or even killed someone.
"Our message is simple '“ do not trespass on the railway otherwise you risk your own life and the safety of others."
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