Up to 1,000 bus drivers across Adelaide have gone on strike, demanding safer conditions and better pay.

Bus drivers began their action at 3am with the strike expected to last for 24 hours, impacting up to 80 per cent of bus services across Adelaide.

The Transport Workers' Union said it had been negotiating with Torrens Transit — the company that operates 80 per cent of Adelaide's bus network — since October over workers' pay and conditions, after the previous agreement had expired.

Adelaide's bus network was privatised by 2000, the same year the Adelaide Metro brand began. 

More train and tram services were put in place to help provide other transport options, but Adelaide Metro users were urged to find an alternative route to and from work or to work from home.

Transport Workers' Union official Sam McIntosh told ABC Radio Adelaide a decision to strike had not been taken lightly.

"We absolutely apologise for [the] inconvenience today and please know this decision to take industrial action ... we never take lightly, and it's a last resort — we need to draw a line in the sand for the future of the industry," he said.

Mr McIntosh said a recent union survey found half of respondents had been assaulted on the job and 25 per cent of those assaults were in the past 12 months.

The union is seeking full screens to protect drivers from being assaulted and is calling for more security on the network and on interchanges across the day, rather than just at night.

He said while some buses currently had screens, they did not go the full length.

"Drivers are getting punched or attacked with a weapon around the screens," he said.

"Clearly it is not adequate and what it leads to is a job that is fundamentally unsafe and no-one is allowed to be surprised that drivers are leaving in droves.

"We also need conditions that mean the drivers actually want to do this job. This used to be a sought-after job, it used to be a really valued job and career."

Drivers are seeking a 14 per cent pay rise and improved conditions in regards to penalty rates and annual leave loading.

Greens concerned over 'dud deal'

Greens transport spokesperson Robert Simms said his party supported today's strike action.

"We are very, very concerned that workers are getting a dud deal and we certainly support their call for better conditions, improved safety and improved wages," he said.

"[The problem] started years ago when we privatised the bus network and we are seeing this with so many essential services in our state.

"What the government should be doing is looking at trying to bring our bus network back into public hands, they're talking about doing that with our trains and we welcome that, but they need to be doing it with our buses as well.

"Once we have these services back into public hands then we can ensure there are better conditions and better services for customers."

Government investigates reversing bus privatisation

Industrial Relations Minister Kyam Maher said the government would be looking into the feasibility of returning buses into public hands.

"My colleague [Minister] Tom Koutsantonis's department is looking at the feasibility of when bus contracts come up whether they can be brought into public hands," he said.

"It is a lot more difficult than the trains and trams that was only [privatised] very recently, these arrangements [for buses] were made almost a quarter of a century ago, but it is being investigated."

He said he hoped the parties could come to an agreement soon.

"We would encourage the parties to keep talking, the inconvenience that many South Australians will endure as a result of these sorts of strike actions is disappointing," he said.