The area, near the Hillside Tunnel/Kenishka Passage, has been closed for installation of a new tunnel.
Police say they are getting reports that some students from the nearby Hillside Avenue School have been climbing the fence there and going onto the railroad tracks.
"We had police officers and other neighbors say, kids are crossing over that railroad track, and we don't know when oncoming trains might be coming by," said Cranford Mayor Thomas Hannen.
The town tried a barricade to keep kids out but that didn't work, so they added a taller fence. The trouble is, the fence has been down since Hurricane Irene and was never replaced. So the kids make it a short cut to head to school.
Parents are being urged to warn their children under no circumstances to attempt to cross the tracks since it is extremely dangerous.
It is expected that the tunnel work will be completed in about three weeks.
With the tunnel temporarily closed, children walking to school are only being allowed to access Hillside Avenue School from Centennial Avenue, Wall Street, Collins Street, or Hillside Avenue.
Students are being directed to cross Centennial Avenue at Myrtle Street or North Lehigh Avenue, where guards are present to ensure their safe crossing.