Workers at Network Rail and 14 train operators will now strike on 18 and 20 August, as well as 27 July.
Workers at Network Rail and 14 train operators are to strike on 18 and 20 August in a row over jobs, pay and conditions, the RMT union has said.
It comes after thousands of train operator and Network rail workers walked out in a national strike in June – the biggest of its kind in decades.
It caused disruption for millions of commuters.
On Wednesday, the union announced that it would also stage a one-day strike on 27 July.
Separately, train drivers at eight rail companies have also agreed to strike on 30 July in a dispute over pay, union Aslef has said.
During the strikes in August, some 40,000 workers across Network Rail are expected to walk out.
RMT general secretary Mick Lynch said the government and rail industry needed to understand that the “dispute will not simply vanish”.
“They need to get serious about providing an offer on pay which helps deal with the cost-of-living crisis, job security for our members and provides good conditions at work.”
He said the union would remain open for talks “but we will continue our campaign until we reach a negotiated settlement”.
Andrew Haines, chief executive of Network Rail said: “By announcing even more strike dates, the RMT has dropped any pretence that this is about reaching a deal.”
He said the best interests of passengers and staff is taking “second place to the union’s bosses’ political campaign”.
Earlier this week, Network Rail made workers a fresh pay offer it said was worth more than 5% – but the offer depended on workers accepting “modernising reforms”.
The industrial action in June, Britain’s largest strike in 30 years, brought the rail network to a standstill.