The Transport Workers Union says Cleanaway drivers have been forced to work longer hours to cover roster gaps, with some denied leave because of staff shortages.

It says the company's actions have impacted the ability of the drivers to manage fatigue which could result in accidents.

TWU state secretary Ian Smith said the workforce didn't take the decision to strike lightly.

"Driver fatigue puts every single person on or around our roads at risk," he said.

"Cleanaway knows this because drivers have reminded them time and time again, and yet it's still trying to ram through dangerous rostering changes that will make it harder for drivers to get the rest they need to work safely."

Mr Smith urged the company to return to the bargaining table to negotiate a deal that supported safe rostering.

The strike was expected to disrupt garbage collections across four council areas in Adelaide but a Cleanaway spokesperson said residents were encouraged to leave their bins out as usual.

"We expect there to be some disruptions to household collections on Friday, however we will ensure contingencies are in place to minimise any impact," the spokesperson said.

The company said it would continue to negotiate with the TWU in good faith.

"We will continue to engage transparently with the Transport Workers Union to reach an agreement as soon as possible," it said.

Australian Associated Press