Workers at Chiltern Railways, Northern Trains and Transpennine Express say they will walk out in a dispute over pay but no dates have been set.

A series of large-scale rail strikes have already happened this summer, causing disruption for millions.

“Strikes are always the last resort, but you can see from the votes and turnout just how angry our members are,” said train drivers’ union Aslef.

Mick Whelan, general secretary of Aslef, added that train companies needed to come up “with a proper proposal… to prevent another strike and all the disruption that causes”.

A spokesperson for the Rail Delivery Group, which represents train operators, said: “We want to give our people a pay rise, but to fund it unions must recognise that as an industry that has lost 20% of its revenue, we can either adapt or decline.

“Instead of causing further disruption to passengers and businesses, we urge the Aslef leadership to continue talks so we can change our services to meet new travel patterns, improve punctuality and secure a bright, long-term future for our people.”

Drivers at 12 UK train operators now have mandates to strike, raising the prospect of the largest walkout yet.

What train strikes have already happened?

The strikes already held this summer have particularly affected commuters who cannot work from home and many people travelling for leisure during the school summer holidays.

Train drivers from the Aslef union staged walkouts at nine operators on Saturday 13 August, and at seven a fortnight earlier.

Separately, about 40,000 members of the National Union of Rail, Maritime and Transport Workers (RMT) walked out on three days in late June, with 13 train companies and track operator Network Rail affected. They work in roles including guards, cleaners and maintenance workers.

This was described as the biggest rail strike in three decades. The involvement of Network Rail’s signalling staff across Britain meant half the railway was completely closed and some areas were affected even though their local train operator was not directly involved.

Similar RMT strikes took place on 27 July, 18 and 20 August, this time involving staff at 14 train companies and Network Rail.

On 18 and 20 August, staff in the TSSA union walked out too, describing it as the first day of nationwide, multi-operator strike action by its members in a generation.

A very small number in the Unite union also took part in a strike.

No more strikes by the RMT or TSSA are currently scheduled.

Will there be more strikes?

All sides say they don’t want more, but they could happen if negotiations don’t produce a breakthrough. Unions have to give two weeks’ notice of action.

Lately, the tone of interviews has suggested significant disagreements remain.

The RMT’s Mick Lynch said talks would continue this week to seek a solution, before a decision was taken on whether to launch further industrial action. But he said it was “very likely” given the distance between the two sides.

Drivers’ union Aslef only recently started official talks with the Rail Delivery Group.

Negotiations will be complex because they then have to talk to the individual train operators. Aslef’s General Secretary Mick Whelan has said it’s not a one-size-fits-all process.

On Thursday he added: “We are calling on the companies to come to the table with a proper proposal to help our members, their drivers, buy this year what they could buy last year. That is the way to prevent another strike and all the disruption that causes.”

Unions have repeatedly called on the transport secretary to intervene, arguing he is blocking progress and should give employers the flexibility to make an offer that they can accept.

In an interview with me in late June, Grant Shapps acknowledged the government set the mandate for negotiations, and had final sign-off on what was agreed in them.

However, he said it was not his place to get directly involved, it was for unions and employers to solve the dispute between them.

What’s it all about?

Rail bosses say they want to give workers a pay rise. But they and the government insist changes are needed to “modernise” the railway, end some outdated working practices and save money.

They argue that with passenger revenue lower than before the pandemic, and after billions of public money kept services going, neither taxpayers nor passengers should have to pay more to cover the funding gap. So higher wages must be funded by reforms.

However, unions say workers need a pay rise that reflects the rising cost of living. They highlight the RPI measure of inflation is currently over 12%.

They also insist job security, terms and working conditions must not be sacrificed under any changes – some of which they strongly disagree with.

One group of more than 3,000 managers in the TSSA union have voted to accept a pay offer from Network Rail, which runs and maintains the infrastructure.

The government and Network Rail have called for other groups of workers to be able to vote on a similar offer. That was for a 4% pay rise in the first year and 4% in the second – which Network Rail describes as an 8% deal over two years.

There would also be a guarantee of no compulsory redundancies during that time, and benefits such as discounted rail travel for family. However part of the second year’s increase would be conditional on reforms.

Unions point out the offer is still below inflation – RMT General Secretary Mick Lynch has called it “puny” – and say they’re not against modernising, but they have concerns over the impact some changes could have on safety.

Plus, that offer is from Network Rail and not the train operators – so it only applies to about half the workers who took part in the national strikes.

Things aren’t as far advanced in negotiations between the train companies and the RMT, although discussions continue. The only potential pay rise that’s been talked about since June has been 2% plus 1% conditional on reforms.

Another bone of contention between Network Rail and the RMT has been changes to the way maintenance teams work.

This would involve job losses which Network Rail hopes could be achieved voluntarily. It has started a formal consultation designed to push through the changes whether or not the union agrees.

The RMT and TSSA are also campaigning against plans to close most ticket offices.

The Rail Delivery Group insists no decisions have been taken, and they’re speaking to the unions about moving members of staff out from behind glass windows into the public area to provide face-to-face assistance.

It also says there’s been a huge drop in the number of passengers using ticket offices in the past decade.