CUNNINGHAM Highway motorists were forced to swerve to avoid debris after a truck carrying a 40-tonne excavator crashed into the Swanbank Rd overpass.
Police said the truck hit the bridge just after 10.30am, while Warwick-bound on the highway.
The truck somehow continued on after the impact and was only intercepted at the eight mile intersection, just outside Warwick - about 100km from the bridge strike.
Ipswich communications room co-ordinator Sergeant Jose Alonso said engineers were trying to ascertain the extent of damage caused to the bridge.
"On first inspection it looked like the damage was quite extensive," Sgt Alonso said.
"Parts of the bridge fell to the ground and a net had to be set up after the highway was reopened to catch any other pieces that may have come off."
Traffic was diverted while inspections were carried out.
Police said the Cunningham Hwy Warwick-bound was reduced to one lane at the Swanbank exit, while traffic on the bridge itself was only allowed to pass in one direction at a time.
It was understood that those arrangements would continue at least until inspections were complete.
The incident occurred only a short distance from the Ripley Rd overpass, where a bridge strike at the beginning of 2012 prompted a drawn-out project to increase the clearance height.
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