A pay dispute between a bus company and the Transport Workers Union which sparked strike action and frustrated Victorian passengers has been referred to the Fair Work Commission.
About 600 CDC Victoria drivers struck for 24 hours on Tuesday, shutting down more than 70 routes in Melbourne's east and west as well as in Ballarat and Geelong.
More industrial action is flagged for Friday and next week amid demands from the union for a four per cent pay rise, as the company offers 2.5 per cent.
State government contractor CDC late on Tuesday confirmed it had applied to the Fair Work Commission seeking mediation following a fruitless meeting with the union.
Throughout the day, nearly 50 canned routes in Melbourne's east and west and 25 services in Ballarat and Geelong left many commuters stranded and angry.
"When buses 160 and 161 are running they're rarely on time," Damian Fleming wrote on Public Transport Victoria's Facebook page.
"But today's industrial action has made things 10 times worse."
"'Possible' service disruptions to CDC bus services today ... why don't you just say 'buses cancelled'? Even your app doesn't say buses cancelled," Sarah Barker Hong wrote.
"No prior notification at our local train station! Not happy!"
Buses are set to resume from Wednesday's first service but a four-hour strike is planned for the same routes between 2pm and 6pm on Friday.
Similar action is also likely for the following Tuesday and Friday, after Victorian children return from school holidays, and in coming weeks may extend to another bus operator, Transdev.
"We have not taken strike action in the bus industry for 20 years," TWU national vice president John Berger said.
"This (pay) claim is not limited to CDC, it's across the bus sector and there are another 600-odd drivers with Transdev who might also take action."
CDC Victoria chief executive Nicholas Yap said Tuesday had been a "difficult day" and apologised to customers.
He added the company's pay offer included "industry-leading benefits".
Drivers are also seeking a one per cent increase in superannuation.