Members of the UK's biggest rail union began their latest walkout at midnight - it will last 48 hours
Just one in five trains are expected to run on Friday and Saturday, hitting services throughout England, Scotland and Wales
A spokesperson for the Rail Delivery Group, which represents train companies, says constructive talks are continuing as part of a "painstaking process"
RMT Union boss Mick Lynch tells the BBC there needs to be "a bit of goodwill from all parties" to find a solution
Other workers - including traffic officers in northern England who work on motorways - are walking out for the first time today
And Abellio bus drivers in south and west London who are in the Unite union are also on strike for 48 hours
The cold weather meanwhile continues with heavy snow in central Scotland
That's it for our live coverage of the rail strikes today, thanks for following along.
You can read the latest about the action affecting services across the UK here, and keep up to date with the latest weather information here.
This page was written by Jo Couzens, Anna Boyd, Emily McGarvey and Sam Hancock. It was edited by Jeremy Gahagan and Chris Giles.
Image source, ReutersWe're going to pause our live rail strike coverage soon, but before we go, here's a roundup of today's main events:
Today's rail strike is set to continue into this evening and throughout tomorrow, meaning many services will either not be running during rush hour or will finish early.
You can find a complete list of affected operators and information on when their trains will run on the National Rail, external website.
Meanwhile, Network Rail is advising people to only travel if absolutely necessary.
In London, the strike has caused severe delays on the Elizabeth line, while the Bakerloo, and the Overground are all part-suspended. A number of other lines are also experiencing minor delays.
On the roads, National Highways, external, which manages motorways and major A roads in England, is not currently reporting any issues from traffic related to the strikes or resulting from the cold weather.
Traffic Scotland, external, the equivalent body for Scotland, is warning motorists of the risk of snow and ice in Highland and Western Isles, Grampian, Central, Tayside & Fife, the regions of Strathclyde and the Southwest, Lothian and Borders.
Image source, .As we've been reporting, the UK's industrial action is not limited to today's walkouts by rail staff, bus drivers and highway workers.
Weeks of disruption are expected as a result of pay disputes and strikes across numerous sectors.
It's not just teachers, nurses and rail workers - more strikes in more professions are due to take place next week.
If you're not sure why people go on strike, or how the whole system works, this quick rundown will get you up to speed.
Amid nationwide strike action across various sectors - rail, mail and nursing - teachers in Scotland are due to stage their own walkouts in the New Year.
Action on 10 and 11 January is planned, with one day targeting primaries and the other secondaries. It follows similar strikes across the country in November and just last week, all of which led to schools being closed.
Teachers in Scotland recently rejected a 5% pay increase offer, arguing instead for 10%. A new offer, which included rises of up to 6.85% for the lowest paid, was dismissed by the country's largest teaching union as "insulting".
The action could well spread to other parts of the UK too, with a number of ballots about whether to strike currently open in unions that would affect schools in England and Wales.
Image source, SSENAbout 1,600 properties in Shetland remain without power as engineers try to restore supplies after heavy snowstorms disrupted electricity supplies at the start of the week, leading to a major incident being declared.
Teams of engineers travelled by ferry to Shetland during the week to help. About 150 engineers are now battling snow and ice to rebuild Shetland's overhead power lines and reconnect properties to the network.
Energy firm Scottish and Southern Electricity Networks (SSEN) said it aimed get the majority connected by the end of the weekend.
However, some "small clusters" on the west side of Shetland's mainland may not have power back until Monday.
Image source, Graham SmithWith transport networks disrupted thanks to the strikes and the continuing cold snap causing problems for people and businesses across the UK, delivery robots have been out and about in the snow in Cambridge helping out in the run-up to Christmas.
But it seems the icy conditions proved too much for one of the little helpers as it tried to mount an icy kerb.
Graham Smith says he came across the "poor little mite" struggling in thick snow blanketing Cherry Hinton.
Starship Technologies, which run the robots, says they were designed to run at temperatures as low as -20C (-4F).
Image source, Harry BellA photo taken on Sunday shows several of the robots merrily trundling along a snowy pavement in the city.
But the following day Graham says he spotted the autonomous bot in trouble.
"Wheels spinning like crazy," he said in a Facebook post. "We gave it a push onto the path, it very politely thanked us and carried on its way.
"Should it have been let out on its own in these weather conditions? It didn't even have a scarf."
He says he lifted it up to help it on before it "shunted backwards and forwards a bit, and then said 'thank you very much' before heading away".
We haven't seen the last of the snow yet, with more set to fall across the UK this weekend, bringing further travel disruption in already icy conditions.
The Met Office's weather warnings include yellow alerts for:
Heavy snow is causing major problems on the roads and for air travel in central Scotland, with some schools shut.
But the cold snap is due to end as milder air and rain move in later on Sunday and much of the country will see highs of 13C (55F) on Monday according to the Met Office. Read more here.
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Theo Leggett
International Business Correspondent
Image source, PA MediaThe smattering of passengers at King's Cross in London this morning
“They can have change, and we accept that they want change, and maybe there’s a need for it”.
The words of RMT leader Mick Lynch this morning. They may prove significant.
Last night, union leaders met with rail companies and the rail minister, Huw Merriman. And now, there is just a hint that a deal could be done. The mood music seems to have changed.
The RMT wants more pay for its members. But it also wants to protect jobs and has ruled out significant changes to working practices.
The rail firms insist more pay can only come if employees accept the need for reform.
For months, the two sides have seemed entrenched in their positions, with no sign of genuine movement.
Today, Lynch told one broadcaster he thought a deal was "achievable" if the industry made new offers on pay and compromised on some of the planned changes.
This looks like progress, or at least a sign progress is possible.
But for a deal to be done, compromise will be needed on both sides. And progress will have to be made quickly, if further confrontation and industrial action is to be avoided.
Sam Hancock
Live reporter
Image source, ReutersLet's take a step back and get a sense of what the government says it believes needs to be done to deal with the current NHS strike action.
On a trip to Belfast, Northern Ireland, PM Rishi Sunak made clear today that a revised pay offer is not being considered for nurses.
He told the BBC that Health Secretary Steve Barclay's door was "always open" for talks - but the government would only consider what it believed to be "fair" and "reasonable" terms.
The Royal College of Nursing (RCN) has demanded a rise of 5% above the RPI inflation rate - currently over 14% - but the government says this is unaffordable.
The RCN trade union has accused ministers of being "disingenuous" over their "door always open" offer, claiming they are not willing to discuss pay at all.
Sunak also used the interview to insist the government had followed recommendations made in a report by an independent NHS pay review body back in February. But Jerry Cope, the former head of that body, has already said the offer is “probably out of date” in light of soaring inflation.
The PM's facing pressure from within his own party as well, with some Tory MPs breaking rank to criticise the standoff. Those who have gone public so far are:
We'll have to wait and see what the PM's intervention means for nurses, who are next due to walk out on 20 December.
Image source, PA MediaAs we've been reporting, the Royal College of Nursing has suggested further strike action if Health Secretary Steve Barclay does not agree to reopen pay negotiations.
The government said nurses' demands for a 19% pay rise are unaffordable and it has followed the recommendation of an independent pay review body in setting wages.
Former Health Secretary, Lord Lansley, says reopening pay discussions would "simply bust NHS employers' budgets this year and would have very damaging consequences for their ability to provide services over this winter".
He says the government wants to ensure NHS staff are properly rewarded and recognises "very practical issues of recruitment, retention and motivation".
"That doesn't mean we should abandon independent pay reviews... It's been around for 35 years and it's a protection for NHS staff that their pay should be the subject of an independent review," he tells Radio 4's World at One programme.
Lord Lansley adds that the government should give greater confidence that the next pay award will meet the needs of the NHS by publishing their evidence and recommendations to the pay review body.
Heavy snow has been disrupting travel in central Scotland.
A Met Office amber warning for snow in the area has now ended but police have issued a travel warning for the whole of the country and are advising people to travel with caution.
There is also a yellow warning for snow and ice which remains in place until 21:00.
Find more live updates on the weather in Scotland here.
Meanwhile, some people in Scotland have been sending in their snaps of snowy scenes.
Details of how to send in your pictures are here.
Image source, WeatherWatchers/Mrs KStirling
Image source, WeatherWatchers/NellingtonMethven, Perth & Kinross
Image source, WeatherWatchers/HarWoodside, Perth & Kinross
Hannah Miller
BBC Breakfast business presenter in Halifax
At The Piece Hall in Halifax, traders are aware some of their customers are facing tougher times, with budgets being squeezed and disruption in the run-up to Christmas.
Melanie Thompson runs a wine and cheese shop at the one-time cloth hall in the town, which sits between Manchester and Leeds.
She says the strikes are affecting who comes through the door.
"We’re not seeing as many people travel from further afield but local people who might have visited bigger cities are spending with us instead."
Melanie says she is hoping the postal strikes will lead to a last-minute dash to buy presents in person, as customers may not want to rely on online deliveries.
You can keep up to date with the latest on the planned strikes here.
Image source, Getty ImagesElsewhere, Unite has just announced that about 1,200 workers at Rolls Royce Motor Cars' plant in Goodwood, West Sussex, have won the biggest single pay deal in its history.
It is worth up to 17.6%, far above the rate at which the cost of living is going up.
It means that a typical worker's pay in the plant will go up by £3,205, as well as receiving a one-off payment of £2,000.
Workers at the factory produce some of the world's most expensive luxury cars, including the Ghost and Cullinan.
The union says the win showed "it is high time workers had their well-earned share of that reflected in their pay and conditions".
We learnt yesterday that TSSA staff who are on strike have reached a deal with Network Rail over a pay offer.
Dr Ashok Kumar, a professor of political economy at Birkbeck University, tells the BBC that the development could be a "good sign" for other union negotiations.
Dr Kumar suggests that if the 9% pay rise agreed with the TSSA was also offered to the RMT, "without changes to the labour conditions, what they're calling modernisation" more progress would be made.
He adds: "It doesn't make much sense that the government isn't actually making more progress on this you know.
"There's a level of empathy and sympathy [for railworkers] that really is unprecedented in British history."
If you're unsure what's behind the wave of strikes hitting the UK, the BBC's Make Sense of Your World series has made a short film exploring the key issues.
It looks at who's taking action, why now, and how the situation might be resolved.
Watch the film here.
Image source, PA MediaIf you're just joining us or need a catch-up, here's the latest on this morning's rail strikes:
Image source, PA MediaThe fixture will now be played at The Stoop
Turning to sport now and the Big Game at Twickenham between Harlequins and Bristol Bears, which was due to host 82,000 spectators, has changed venues because of the rail strikes.
The fixture on 27 December, which was sold out, will now be played at The Stoop stadium with a capacity of 14,800, meaning many ticket holders will not be able to attend.
In a statement, Harlequins said: "Despite 27 December not being a designated day for industrial action, the club has been informed this week that mainline train services into Twickenham station will not operate at all on the event day, alongside severe restrictions across the train and underground network feeding the local area."
Laurie Dalrymple, the club's chief executive, said: "Ultimately, we must put the safety of our supporters and those working at the event first.
"It is clear that, without the functioning rail network, we cannot safely deliver a large-scale event at Twickenham."
Harlequins added that the annual showpiece Big Game 14 event at Twickenham stadium would now take place on 4 March and Harlequins would face Exeter Chiefs in a change of opposition.
Nick Miller
BBC Weather
After a morning when the lowest temperatures across the four home nations have fallen to -9 to -13C, it’s hard to believe that by Monday, highs are likely to be in the range of 10 to 15C above freezing.
But the transition to milder weather will bring a further spell of disruptive snow and ice on Sunday before it turns to rain.
Anyone with travel plans on Sunday does need to keep a close eye on the Met Office weather warnings for their area.