A spokeswoman for NSW police confirmed the male truck driver had died following the incident near the intersection of River Forest Road, close to a popular spot known as 'Pooh Bear Corner'.

The man had been travelling south on the Kings Highway near Braidwood when his truck rolled around 8am.

Emergency services and police were still on the scene as of 1pm Saturday. A Fire and Rescue spokesman said the the cabin of the truck had been crushed.

Traffic was affected in both directions, backed up for several kilometres along the Kings Highway, with delays easing but expected to continue into the afternoon. One lane was initially closed and alternating 'stop slow' traffic control measures remained in place.

A Canberra woman told Fairfax Media she was on route from Batemans Bay when saw the accident blocking off traffic about 9.20am.

"It was on one of the hairpin turns," she said. "There were at least six police cars, fire and rescue and ambulance all there and they were still getting the person out of the car when we went by.

"I heard sirens earlier around 8.30am."

There were further traffic delays along the Kings Highway on Saturday afternoon, following a multi-vehicle accident at Nelligen. No serious injuries were reported in the crash and the road was cleared around 2:20pm.

25 people have now died on NSW roads this year and police are urging motorists to take care over the long weekend.

An investigation into the circumstances surrounding the Clyde Mountain accident was underway and the driver of the truck had not been identified.

A Batemans Bay woman said traffic in the area was still heavy at 12.30pm.

"I'm coming down the mountain, but no traffic is moving this way, it's only coming up," she said.

For the latest on traffic conditions, motorists are advised to check www.livetraffic.com.

With Katie Lockley