Staff on South Western Railway are to be balloted on strike action in a dispute over the continued use of guards on services.
The RMT union says it wants "water-tight" promises over the future of the role - which it says are crucial to safety on trains.
The railway usually runs services between Devon, Dorset and Waterloo.
Rail services have returned to normal after a 24-hour strike disrupted First Great Western services in the region.
Members of the RMT Union walked out in an ongoing dispute over the introduction of high speed trains in 2017. 30% of Sunday services were affected.
Further talks are being held in Bristol today in an attempt to avert another strike.
A three-day stoppage is planned over the Bank Holiday weekend by the RMT union, on top of yesterday's action.
The dispute is over the buffet service and the role of guards on new electric trains being introduced in 2017.
Train cleaners on First Great Western services have just started a 24 hour-strike for improved pay.
They've rejected a 2% offer from sub-contractors Mitie.
The RMT union members are also calling for an end to zero-hours contracts which offer no guarantee on working hours.
The RMT union has announced that Friday's strike planned for CrossCountry Trains has been suspended after "significant progress" was made in talks.
The action was being organised by workers in protest at a range of issues, including training, and the use of league tables to record performance.