It is only months since a truck hauling an excavator blocked a tunnel on the major Canberra road for several days, leading to a $1.2 million insurance bill.

During Thursday's incident, the truck was carrying a wall of pre-cast concrete and hit the nearby Commonwealth Bridge, shutting down one westbound lane about 2.30pm, ACT Policing said.

Motorists were warned of delays, but by about 3.45pm the truck had been extracted from the bridge and the lane reopened by police.

There were no reported injuries, while the bridge suffered what looked like minor damage where tiles above the road had crumbled.

A spokesman from WorkSafe ACT said inspectors were at the site, but had determined the matter needed no further investigation.

The scenario felt all too familiar for some, who compared it to the truck crash last October that shut down traffic on the arterial road for more than 48 hours.

The repair bill for that crash was $1.2 million, which doesn't include the $260,000 incurred by Roads ACT for the immediate clean-up.

The crash was one of two on Canberra's roads on Thursday afternoon.

A four-car prang on the intersection of Gungahlin Drive and the Barton Highway closed two lanes of traffic about 2.15pm.