South Australian drivers are furious after a section of a major highway in the state's south-east developed deep cracks, leaving them  "dodging potholes" fewer than six months after the road was upgraded.

Asphalt resurfacing works were undertaken along a 2.5km length of the Southern Ports Highway, between Beachport and Millicent, in May of this year to correct the road shape and improve the overall condition.

The road required a further spray seal surfacing to be applied over the asphalt to waterproof the pavement, however weather conditions affected this.

The Department of Infrastructure said the "area experienced heavy rain before the surfacing could be applied and the continuing wet conditions had caused moisture to enter the pavement causing potholes".

Further concerns were raised around the white lines not yet being painted — they should have been completed by August — and the speed limit still being capped at 80kph. 

Heather Burdon, from the Beachport Community group,  said it was not just the Southern Ports Highway — all the roads across the region were in poor condition.

"There are no edges to the road, just drop-offs. Numerous people have reported dented rims, tyres, shredded blowouts.

Ms Burdon said it was not enough to keep fixing the issues when they arose — the Southern Ports Highway needed a complete overall.

"The road is way past its use by date. It was meant to last about 30 years and the Southern Ports Highway is definitely older than that," she said.

She said the repairs should have been better planned and the weather should have been expected.

"Why would they be trying to do that sort of work In the south-east in May and June?

"It's just dangerous," she said.