Truck drivers who lose control at the bottom of the South Eastern Freeway during upcoming road resurfacing works will be expected to drive into the back of a stationary truck to stop themselves.
In a notification about the works, the Transport Department said one of the two arrester beds at the bottom of the freeway would need to be closed at certain times.
Instead, it will provide a truck-mounted attenuator "for use by any errant heavy vehicle".
The head of the South Australian Road Transport Association, Steve Shearer, described it as a "very innovative, but mentally challenging approach".
"It is basically a rigid truck with a massive rear fender with a huge shock absorber system built into it," he said.
Mr Shearer said he would spend time educating both local and interstate truck drivers about the changed conditions.
"From an engineering point of view there's no question, this works," he said.
"It's been used elsewhere in the country and on some roadworks with lower speed events to protect the road workers, but the point we've made is it's counter-intuitive for a truck driver.
Intersection notorious for serious crashes
The intersection at the bottom of the South Eastern Freeway has been the scene of several fatal accidents involving out-of-control trucks over the past decade, including a crash in August 2014 that killed two people.
It also has a history of chilling near-misses, including an incident in September 2019 where the driver of a B-double ran a red light at the intersection after the truck lost its brakes.
The crash in 2014 prompted new rules forcing trucks to use low gear rather than brakes to manage the steep descent into suburban Adelaide.
Mr Shearer said he had been briefed by the department and understands the truck mounted attenuator would be placed on the city-side of the Heysen Tunnels, on the uphill track.
He said during some of the works all vehicles making the downward descent would have to cross onto the uphill track, in what is known as contraflow.
Once they pass the Heysen Tunnels, they would be directed back on to the downhill track.
Mr Shearer said the problem would be getting drivers of out-of-control vehicles to understand they are supposed to collide with the attentuator.
"If they all come over the top of the hill at correct speed in low gear, they won't get into any trouble," he said.
"I actually think what the contractors and the department have come up with is brilliant, the key to making it really work is getting the messaging out to the public.
There will be a 40km/h speed limit during the roadworks, which are due to start this Sunday.
The $35 million resurfacing project is expected to be completed in six months.
