Train driver RMT members at 14 rail operators will take strike action on February 1 and 3 over jobs pay and conditions.
This includes Great Western Railway (GWR) which runs services in Devon and Cornwall.
The decision by the union to strike on February 1 coincides with a TUC day of action where several unions are coordinating their strikes during the cost-of-living crisis.
RMT general secretary Mick Lynch said: "Our negotiations will continue with the rail operators to create a package on jobs, conditions and pay that can be offered to our members."