Calls are growing for extra safety measures on Adelaide's South Eastern Freeway after a crash involving a truck, a bus and seven cars that "miraculously" caused only minor injuries.
Nine people were hurt after a truck towing a trailer was unable to stop at the base of the freeway on Sunday and ploughed into a bus and other vehicles as it careered through an intersection.
The truck's driver, a 60-year-old man from Queensland, was the most seriously hurt and remained in hospital on Monday with non-life threatening injuries.
His rig rolled during the incident.
The crash prompted calls from the Transport Workers Union for greater safety measures including an extra arrester bed near the end of the freeway, a cut in the speed limit for heavy vehicles from 60 to 40km/h and compulsory training for drivers on navigating steep descents.
"Yesterday's accident was a frightening incident that has yet again displayed to the state that the South Eastern Freeway is a tragic accident waiting to happen," union branch secretary Ian Smith said.
"We are lucky that no one was killed but if nothing is done about the safety on the descent of the freeway, then it's just a ticking time bomb."
SA Police Superintendent Bob Gray said while the crash was still subject to an extensive investigation, "it's absolutely miraculous that nobody was seriously injured or killed".
He said police hadn't yet been able to speak with everyone involved, including the truck driver, but indicated reports of smoke coming from the truck would form part of the investigation.
Premier Peter Malinauskas said while the state government was willing to explore extra safety measures for the freeway, it was first important to determine the cause of the crash, be that driver error or a mechanical failure.
The premier said the issue of an extra arrester bed, to give trucks a final escape route, wasn't without complexity given the physical constraints of the area.
"We're certainly open-minded to explore that issue to make sure the right decisions have been made in the past," he said.
"Obviously the scale of the accident is something that is truly extraordinary.
"But we've got to make sure this isn't just a great escape."
Mr Malinauskas said it must be ensured that "all the appropriate settings are in place" to prevent these types of accidents.
The base of the freeway - where hills commuters, trucks and people driving to Adelaide from the eastern states converge - has been the scene of a number of serious crashes and near misses in recent years.
In one of the worst incidents, two people were killed in 2014 when a sewage truck suffered a major brake failure and crashed into two stationary cars.
In the wake of Sunday's crash, the SA opposition called on the state government to expedite a planning study to bypass freight around the freeway and the city.
Transport spokesman Vincent Tarzia also welcomed renewed discussion around an extra arrester bed.
"South Australians deserve to feel safe when travelling on the South Eastern Freeway and are rightly horrified by this latest frightening crash," he said.
"All options must be looked at because it's clear lives are at risk right now."