DAMAGE to the railway bridge at Rosehill Rd on Warwick's northside from a heavy vehicle incident is expected to be fixed by tomorrow afternoon and the Allora back road re-opened.

As reported the bridge, near the John Dee abattoir and with a height limit of 4.4 metres, was damaged late on Monday when a prime-mover and low-loader trailer transporting an excavator struck it.

Queensland Rail and the Department of Transport and Main Roads (TMR) immediately cordoned off the bridge for safety reasons and diverted traffic.

A Queensland Rail spokeswoman said yesterday the bridge was expected to be fully repaired by 5pm tomorrow.

"What has happened is that the bridge has been pushed out of alignment by about 80cm," the spokeswoman said.

"Our crew working on the site is confident they will be able to complete the repairs in the expected timeframe."

Someone who could be in for a shock is the driver of the truck or its owner, who will most likely be liable not only for the cost of the repairs but a fine as well.

"Motorists who damage Queensland Rail infrastructure can be fined up to $8800, in addition to the repair bill," the spokesperson confirmed.

The driver was taken to hospital for observation on Monday evening after the excavator accidentally tipped off the trailer during the recovery process. He was in the cabin of the machine at the time but was not injured.

A Southern Downs Regional Council spokeswoman said it had created detours but it was the final call of Queensland Rail and TMR as to when the road would re-open.

SDRC Director of Engineering Services Peter See said traffic today and tomorrow would continue to be detoured around the site, along Oehlmann and Ogilvie Rds and Lyndhurst Lane, with heavy vehicle drivers reminded that Lyndhurst Lane has a 12-tonne load limit.