The former Barton Buses part of Trentbarton is facing four consecutive Mondays of strikes, starting on 10 September in a pay dispute.
The company hopes to be able to run some services on the 11 affected routes.
Routes from Nottingham are expected to be affected after 76 of the 164 union members voted to strike, in a ballot in which 108 members voted. The former Barton Buses part of the business employs 230 drivers, of the 1,000 employed as a whole by Trentbarton, and retains separate contracts and pay negotiation dates.
A 2.5% pay award was implemented in June, backdated to April, but Unite wants a 3% award.