Bus drivers in Gloucestershire and Herefordshire are set to take industrial action in the run-up to Christmas over a pay dispute.
Stagecoach workers in Gloucester and Ross-on-Wye are angry that they have been offered a smaller pay-rise than colleagues elsewhere.
The action - which was backed by 67% of drivers - includes an overtime ban and could escalate to walkouts.
Union leader Trevor Hall said he hoped public disruption would be minimised.
Stagecoach management have been given 10 days notice of the action, which could start on 19 December.
The Gloucester and Ross drivers say they have been offered a 2% rise, but their equivalents in Cheltenham have been given a 4.5% increase.