Wellington commuters will be left to their own devices on Wednesday for five hours while bus drivers walk off the job over stalled contract negotiations.

The Wellington Tramways and Manufacturing and Construction unions said bus operators working for GO Wellington and Valley Flyer will be undertaking strike action between 9am and 2pm.

GO Wellington, Valley Flyer, Mana Coach Services and the unions were about to enter into negotiations around the unions' claim for a regional Collective Employment Agreement to cover all three companies, which would affect approximately 280 GO Wellington and 100 Valley Flyer union members, NZ Bus general manager operations Zane Fulljames said.

"We advise customers to make alternate arrangements for their travel on Wednesday from 9am. With the strike not occurring until 9am and a return to work at 2pm we anticipate school services will not be impacted at either end of the day."

The Airport Flyer service would still operate during the strike period, Mr Fulljames said.