Canterbury flooding: Truckies finally get access to State Highway 1 Ashburton Bridge

Heavier vehicles can once again drive on the flood-ravaged Ashburton Bridge, in what will be welcome news for truck drivers.

All trucks - except for those with overweight permits - can cross the bridge between 7am and 7pm, the NZ Transport Agency (NZTA) said on Thursday.

Light vehicles now have permanent access to the bridge.

The bridge, on State Highway 1, crosses the Ashburton River and is the primary transport route for southbound travellers. It closed on Tuesday morning after days of wild weather in the Canterbury region.

"Pier testing yesterday, using heavily-laden trucks, showed negligible movement, indicating that the pier has stabilised and the structure is robust," said Waka Kotahi NZTA system manager Pete Connors.

He said caution is needed as debris is still being removed from underneath the bridge.

"We need to keep monitoring the bridge deck and the pier for any movement during the day. 

"After a week of use, we need to reassess the situation and decide if we can allow broader access for the freight industry."

An Ashburton bypass opened on Tuesday night after the wild weather also knocked out alternative routes. Trucks with overweight permits will have to keep using the detour for the time being - adding at least an hour to the journey.

"When you're running big trucks it all adds cost so getting this route open again is pretty for moving freight and keeping the freight cost-effective," Ashburton District Mayor Neil Brown said.