Police investigating the Selby train crash are concentrating their inquiries on how a vehicle came to be on the railway line.
GNER's high-speed passenger train travelling from Newcastle to Kings Cross hit a runaway car and then collided with a freight train. At least 13 people died in the accident.
A Highways Agency spokesman said the M62 bridge has a standard 30 metre-long barrier in place before vehicles get to the actual bridge.
Inspector Steve Page, of Humberside Police, said the force was now examining how a Land Rover, which was pulling a trailer, came to be on the track.
It is suspected that the driver, a 36-year-old Lincolnshire man, suffered a blown-out tyre which caused the vehicle to veer off the motorway before it reached the bridge over the rail line.
The M62 bridge was built in 1974 and is one of 589 Highways Agency bridges over railway lines, of which 230 are motorway bridges.
Highways Agency representatives joined Railtrack, British Transport Police, the HSE and a six-strong team from the Transport Research Laboratory in Crowthorne, Berkshire, at the accident scene.