Three youths were recorded on CCTV interfering with the telephone used to contact the signaller at Ducketts Crossing in Daleside Road, Pudsey.
One jumped onto the tracks before running across the line to get to the telephone box.
Inspector Granville Sellers, of BTP in Leeds, said Ducketts Crossing was the most problematic in the Leeds area. There were 30 incidents at the crossing in a three-year period.
Insp Granville said: “These lads were just larking around but level crossings are dangerous places and they need to be used properly.”
News of the investigation into the June 6 incident comes as British Transport Police launches a campaign to warn people about the dangers of trespassing or failing to stop for signals at level crossings.
In the last year there were 24 such offences in the West Yorkshire area.
BTP recorded 3,615 offences at crossings nationally in the last year, with incidents ranging from trespass to failing to stop at signals.
The majority were motorists who failed to obey signals and warning lights.
Officers are carrying out extra patrols close to crossings and are visiting schools to give safety talks during Operation Look this week.
As part of the campaign, the Yvonne Arnaud Theatre Group will also be performing monologues from their play, Off The Level, close to problem crossings.
Inspector Becky Warren said: “We will not hesitate to enforce the law, but convincing people to change their habits at crossings is a vital part of what we do.
“We spend a lot of time talking to schools and businesses about the importance of safe level crossing use, and we want to use this week to engage with the public who use level crossings on a daily basis.”
Darren Furness, head of level crossings at Network Rail, said: “Britain has one of the safest railway networks in the world. However, level crossings do pose a risk and everyone needs to take care when crossing.”