Truck drivers and their families have blocked a main road leading into Adelaide's CBD to protest against unsafe driving conditions.

They gathered on King William Road in response to last month's crash at the start of the South Eastern Freeway that resulted in the death of two people in stationary cars when they were hit by an out-of-control truck.

A similar accident involving an out-of-control truck killed a man standing at a bus stop near the same intersection four years ago.

On Tuesday police cleared the intersection as yet another truck barrelled through the intersection without being able to stop.

Tony Sheldon from the Australian Workers Union said drivers were being pressured to cut corners and wanted better working conditions.

"We're literally seeing South Australians die on our roads," he said.

"We're seeing this pressure being applied where people around the country are losing their lives, our mums, our dads, our brothers and sisters and our children."

Mr Sheldon said economic pressure on trucking companies not to maintain their vehicles had resulted in truck drivers being pressured to work "extraordinary hours".