Adelaide's South Eastern Freeway has reopened to all traffic after a chicken truck rolled over, blocking all three lanes of the down track for six hours.

Key points: A semi-trailer carrying chickens rolled over on Adelaide's South Eastern Freeway

A semi-trailer carrying chickens rolled over on Adelaide's South Eastern Freeway All three citybound lanes of the road had been closed at Crafers

All three citybound lanes of the road had been closed at Crafers Trucks and buses were unable to get through to Adelaide

Police said the B-double semi-trailer, which had been carting live chickens, jackknifed past the Crafers turn-off about 3:30am.

The road was blocked until 9:30am.

All cars from the Adelaide Hills to the city were diverted down Upper Sturt Road or via Greenhill Road.

Large trucks were not able to use these narrow roads.

More than 100 trucks had to wait to get through until the road reopened, while others were diverted farther east.

Buses were delayed but got through to Adelaide.

"The only thing we can do is ask for people's patience as this is dealt with as soon as possible," Transport Minister Stephan Knoll said.

The truck hit electronic speed signs when it crashed.

"They've got a truck up there ready to get the chickens on board," Senior Constable Mick Abbott said.

"They've got plenty of workers up there. They just have to cut off the power to get SA Power Networks up there as well."

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The RSPCA attended the crash scene.

Spokeswoman Carolyn Jones said the chickens involved in the crash were taken to an Ingham's processing facility at Burton in Adelaide's north where their welfare would be assessed.

Up to 1,000 chickens died.

"Clearly a very distressing scene with so many crates that had toppled over and many birds that were loose," Ms Jones said.

"We'll be monitoring the welfare of the surviving and the injured birds."

Senior Constable Abbott said most of the chickens were still in their crates.

"There's not a lot of loose chickens around the place," he said.

ABC Radio Adelaide listener Liz said drivers were speeding on Greenhill Road despite a traffic jam caused by the diversion.

"If you're speeding through, you're just going to ram up someone else," she said.

The chicken truck crash soon after it happened about 3:30am. ( ABC News )

South Australian Road Transport Association executive director Steve Shearer said the Department of Planning, Transport and Infrastructure should consider installing gaps in the concrete barriers in the middle of the freeway — or making them removable — to prevent similar issues.

"I think we're going to have some pretty serious discussion with Government soon," Mr Shearer said.

"But in the short term, the only thing that can be done is get a little bit more flexible-minded about the management of those barriers because, politically, time is ticking away — the next election is coming — and people remember this sort of thing."

Mr Knoll said the barriers were important to prevent head-on crashes.

In January, the State Government scrapped its Globelink proposal for a major road around the eastern side of the Adelaide Hills to get trucks off Adelaide roads after a feasibility study found the expense was not justified.

Mr Shearer said the Government should still consider a less expensive alternative.