More travel disruption is hitting the UK over the next few days, including on FA Cup final day when thousands of people would expect to be travelling by train to see the showpiece game.
Between 40 and 50 per cent of normal services will run on three strike days but there will be wide regional variations, the Rail Delivery Group (RDG) representing train companies said.
Train drivers in the Aslef union walked out on Wednesday, with another day of protest action planned for Saturday, while workers in the Rail, Maritime and Transport (RMT) union are on strike on Friday.
Aslef general secretary Mick Whelan said: "They [managers] seem to want thousands of per cent productivity [increase] for a 20 per cent pay cut."
Passengers are advised to plan ahead and check the times of first and last trains.
Sylvia Lewandowska, 46, an NHS orbital prosthetist at Royal Berkshire Hospital in Reading, said her journey to commute from London Paddington was delayed by an hour, forcing her to reschedule four appointments.
"I have to wait an hour for my train so all my patients will have to wait," she said. "It's affecting my patients because they are from different parts of the UK and many are elderly."
Another delayed passenger at Paddington, Uwe Kraeker, 60, from Freiburg, Germany, said: "It's pretty frustrating.
"I understand people fight for better working conditions and wages but when they strike on public transport they take the rest of the country hostage."
The strikes will affect 15 train companies, with services due to start later and finish much earlier than usual – typically between 7.30am and 6.30pm.
Mr Whelan said at a picket line in Newcastle: "If you spend months in a room, tell people things aren't acceptable to you, then they produce a deal that contains those things, then they are setting the deal up to fail.
"That is a deliberate act on behalf of both the government and the people that we're dealing with. They do not apparently want a resolution."
Train strikes across the UK – in pictures
The RDG said about half of the network would shut down on the RMT strike day.
On Aslef strike days, about 40 per cent of trains will be running but there will be regional variations, with some operators running no services at all.
It is likely that evening services on some lines will be affected on the days before each walkout, so passengers are advised to check the last train times on the evenings before strike days and the following mornings.
Aslef will also start an overtime ban at 15 train operating companies on Thursday that could cause disruption, especially in and out of London.
The strike will affect football fans travelling to London for the FA Cup final between Manchester City and Manchester United on Saturday at Wembley Stadium.
Supporters wishing to travel to the game by train from Manchester on the day have been advised not to do so.
Britain's worst day of strikes in more than a decade – in pictures
Strikes on Saturday will also affect more than 100,000 people travelling to the annual Epsom Derby, music fans travelling to Beyonce’s Renaissance world tour concert at the Tottenham Hotspur Stadium in North London and cricket fans travelling to watch the England v Ireland Test match at Lord’s in West London.
“The upcoming rail strikes called by the Aslef and RMT leadership will not only affect our passengers’ daily commute, but will also impact those travelling to and from the FA Cup final and other events across the country, causing disappointment and frustration for tens of thousands of people,” an RDG representative said.
“It will also inconvenience families who have been looking forward and have planned their half-term holidays. It will also further burden our people who have already lost thousands of pounds at a time of financial strain.
“We understand the impact of these strikes on individuals and businesses alike, and we can only apologise for this unnecessary and damaging disruption.
“While we are doing all we can to keep trains running, unfortunately there will be reduced train services between Wednesday May 31 and Saturday June 3, so our advice is to check before you travel.
“Passengers with advance tickets can be refunded fee-free if the train that the ticket is booked for is cancelled, delayed or rescheduled.”
The unions say they have not been given a pay offer they can recommend to their members.
Officials say support for strikes remains strong among workers as well as the public.
Aslef says train drivers have not had a pay rise for four years.
Both unions claim the government is preventing the train companies making an acceptable offer, which ministers deny.
“These strikes have been co-ordinated by union leaders to disrupt passengers in a week which will see major events such as the first ever all Manchester FA Cup final, the Epsom Derby and a number of concerts and festivals across the UK,” a Department of Transport representative said.
“Not content with impacting the hundreds of thousands of people who have looked forward to these events all year round, unions are also targeting their own members’ pockets by forcing them to miss out on pay every time they strike.
“The government has facilitated a fair and reasonable pay offer, now union leaders must do the right thing and put this to their members.”