The RMT is to hold a fresh strike ballot at South Western Railway in the long running dispute over the role of guards on trains.
The dispute at SWR is the first high profile action subject to new legislation.
The new Government rules mean new ballots have to be held every six months to ensure union members are still in favour of industrial action.
The union has called for more days of action before the current ballot expires.
A three day walkout starting on Friday week and two more days of action in September.
The vote begins on Thursday and will last until early next month.
Saturday 1st September 2018 (48 hour strike)
Sunday 2nd September 2018 (24 hour strike)
Saturday 8th September 2018 (24 hour strike)
Saturday 15th September 2018 (24 hour strike)