The number of passengers at major railway stations was less than a fifth of the normal level as services were affected on the second day of the strike.
Network Rail said the number of people using its stations on Tuesday, the first day of this week’s strikes, was 12-18 percent of normal, and the situation was similar on Thursday.
Euston, Paddington, Edinburgh Waverley, and Liverpool Lime Street were among the stations with fewer passengers than on a typical Saturday.
Broadband provider Virgin Media O2 said “millions more are working from home” this week.
On Tuesday, its use increased by 10%.
As many as 40,000 members of the Rail, Maritime and Transport (RMT) Union and 13 train operators walked out of Network Rail on Thursday as bitter disputes over salaries, jobs and conditions continued.
Only one train out of five ran, and was limited to most main lines, with about half the network shut down.
Services started late at 7.30 am and were to close early at 6.30 pm.
The last trains were much earlier than usual, such as London Easton to Glasgow at 1.30pm and London Kings Cross to Edinburgh at 2pm.
The disruption will continue on Friday, with only 60% of trains running, mainly due to delays in starting services as signals and control room staff will not be available for overnight shifts.
Members of Aslef’s drivers’ union in Greater England are walking out on Thursday in a separate pay dispute.
Boris Johnson called the attacks a “terrible idea.”
The Prime Minister said: “I think it is important to remember that these strikes are unnecessary.
“I think people should go around the table and fix it.”
He added: “This is a government that has been investing more in the railways than any previous government in the last 50 years.”
Downing Street also called on unions to end their strikes, saying it was “a question for unions” to move forward with Saturday’s action.
A spokesman for No. 10 said: “We do not want to see the strike continue any longer.”
Frank Bird, senior network planner for National Highways, said Thursday morning traffic flow on motorways and major A roads was “remarkably good.”
“The shape of the network is such that the amount of traffic is low,” he told the PA news agency.
“If you’re going in and out of town and city centers, they’re a little too busy.”
Location technology firm TomTom said the congestion on the streets in London at 9am was 83 per cent, up from 75 per cent at the same time last week.
But traffic levels dropped or only slightly increased in several other cities, such as Glasgow (below 40% to 36%), Liverpool (below 49% to 47%), Manchester (64% to 66%) and Newcastle (49% to 50%).
The figures reflect the proportion of extra time required for travel compared to free flow conditions.
The technology firm, which has more than 120,000 sensors in corporate offices around the world, recorded a 22% occupancy rate in the UK on Tuesday, down from 40% on the same day last week.
Steve Montgomery, head of the Rail Delivery Group, which represents train operators, was asked why rail workers were not being guaranteed that the reforms would not necessarily lead to redundancy.
He told the BBC Breakfast that it depended on the extent of the reforms, the popularity of voluntary separation schemes and how many workers could be retrained.
He added: “We believe that once we work on reforms, we hope we can accommodate everyone who wants to stay in the organization.
“So, we just need to go through the process and see how many people are left, and hopefully not necessarily make anyone useless.”
Further talks were held on Thursday to resolve the dispute, but no solution was found.
Kevin Groz, Network Rail’s head of media, told the Times Radio Breakfast: “It’s about negotiating and taking, and at the moment RMT is just take, take, take.
“We are talking about modernizing the ways of working that are old.”
Eddie Dempsey, RMT’s assistant general secretary, said in a statement that “the people are behind us.”
He told the PA news agency: “They think it is a scandal that billions of rupees are being taken out of our industry while workers are being punished.
“Teachers, they are facing the crisis of cost of living, (also) posts, telecom workers, health workers.
“We think there will be more demands for wage increases in the economy and we think that’s right.
“This is a time when wages in the UK have skyrocketed. Wages have been falling for 30 years and corporate profits have skyrocketed.
A spokesman for Rail Delivery Group said: “Our analysis shows that the RMT figures for train operator profits are inaccurate and based on estimates rather than facts.
The figures, published by the Office of Rail and Road, tell a different story. Last year, 20 train operators made a total profit of £ 75 million with a profit margin of only 0.6%.
“Train operator staff costs increased from £ 3.1 billion in 2017-18 to £ 3.6 billion in 2019-20, an increase of 16%. This is partly due to staff increases, but RMT claims Although there has been no increase in staff salaries, it also reflects an increase in salaries during this period.
“The franchise model no longer exists, and train operators are paid a fixed performance fee in the same way as other government suppliers.”