More than 7000 school students are expected to be inconvenienced by a second statewide bus strike in Tasmania in as many weeks.
State-owned Metro's 370 drivers will stop work on Friday morning, angry their demand for a three per cent per annum pay rise is not being met.
Metro is offering two per cent but says some drivers will be more than 30 per cent better off over three years because of changes to wage classifications.
Chief executive officer Heather Haselgrove says drivers would reach the top rate of pay more quickly under Metro's offer.
"It currently takes 10 years of service to achieve the top level of pay," Ms Haselgrove said in a statement.
Around 13,000 commuters are expected to be affected, half of them students.
Motoring organisation RACT is warning Hobart could experience some of its worst ever traffic on Friday morning.
"Holding the state to ransom really is what I see this company doing, not the workers," Unions Tasmania boss Kevin Harkins told ABC radio.
Drivers previously stopped work for four hours last Thursday and the Rail, Tram and Bus Union says it will also take action next Tuesday evening.