Train drivers at South West Trains are to hold a four-day strike in a row over pay and hours.
The Aslef union said its driver members would walk out from 31 March until 3 April.
The union said the dispute had arisen from a break-down in negotiations, with a ballot of its members resulting in 73% in favour of industrial action.
The company said it had offered a pay increase of 4.5%, which would give a driver working in the London area a basic salary before overtime of £40,447 for a 37-hour week.
All other trade unions at the organisation have accepted the deal or recommended it to their non-driver members.
South West Trains said it would run at least 300 train services each day and will have buses from sister company Stagecoach Bus at its disposal from depots throughout the UK.
Managing director Stewart Palmer said: “We are very disappointed that Aslef has taken this decision as we believe that this is a very good offer in the current economic climate.”