Tube Strike 2014: As Londoners prepare for more disruption - Why is it happening? Why hasn't it been resolved? Who is to blame?

As millions of Londoners face disruption across the capital after a walkout by RMT workers here's our guide to what's going on and who's to blame...

After battling the crowds and congestion following a walkout by RMT members, Londoners face the prospect of having to do it all again. But what is the dispute about, why hasn't it been resolved and who is to blame?

Here's our quick guide.

Why is there a Tube Strike?

The Rail, Maritime and Transport (RMT) union is taking industrial action over plans to close ticket offices on the London Underground, with the possible loss of 960 jobs.

The next round of strikes includes a 72-hour stoppage from Bank Holiday Monday.

Why does London Underground (LU) want to close ticket offices?

At the heart of the dispute is new technology. LU wants less staff working in ticket halls and claims new ticket machines mean that offices are underused. It plans to replace ticket offices with "customer service centres".

It also has repeatedly said that the changes would involve restructuring, there will be no compulsory redundancies and "not a single member of staff will be forced to leave the company".

Are ticket offices obsolete then?

Not really. 34m people used ticket offices last year, they are particularly useful for people who struggle to deal with the machines. Around 1m people used them to get a refund after being overcharged and 1.4m had their fares adjusted at an office.

Why is the RMT opposed to the changes?

The RMT primarily has concerns over safety.

As a result of the changes the number of stations staffed by just one person will double. The RMT also argue that the changes would make it more difficult for visitors to use the Tube. There are also concerns over access for the disabled.

Commuters could also be affected as less staff will be available to deal with emergencies.

The union is also concerned about uncertainty over jobs, with staff fearing a loss of pay or changes to terms and conditions.

Crucially the RMT wants a review of ticket office closures to see if any are worth saving along with a wider public consultation on the issue.

Aren't Tube workers being greedy?

Ticket office staff generally earn a salary of between £25-27k. The average London salary is around £40,000. In this instance the dispute is about the proposed job losses and safety rather than salary.

Why can't LU and the RMT sort it out?

The union and LU have met more than 40 times since the last strike in February. To no avail.

After the previous strike action it was generally believed that a deal had been done to review station closures as per the RMT request. This has not happened - with LU blaming the RMT for failing to submit ideas. Three other unions the TSSA, Unite and Aslef are also involved in negotiations.

The dispute has been complicated by the death of former RMT General Secretary Bob Crow. Despite his public image Mr Crow was widely seen as a man who would do a deal.

Have the strikes worked so far?

The RMT says the earlier strike action was 'rock solid' a claim dismissed as 'farcical' by London Mayor Boris Johnson.

Mike Brown, managing director of London Underground, said 15% more staff worked yesterday than during the previous strike, though it is worth noting that only RMT staff are on strike this time around.

LU said half of train services ran and two-thirds of Tube stations were open, much more than during a previous strike in February.

Nearly 90% of the usual number of Oyster cards were used on Transport for London's network, according to the company.

But the RMT accused LU of "misleading" the public over the level of services and of leaving platforms and stations "dangerously overcrowded."

When are the next strikes?

The RMT say they will stage another walkout - this time for 72 hours - from 9pm on Monday 5 May.

What chance a deal?

Neither side would appear to be budging at the moment.

The RMT has repeatedly said that if LU agrees to a public consultation on ticket office closures they will suspend the action. At the moment that looks unlikely.

The RMT says...

Acting general secretary Mick Cash: "You cannot turn the crucial issue of Tube safety into a high-risk PR stunt designed to do nothing more than prop up the political position and cuts agenda of this Government and London's Tory mayor."

London Underground says...

Mike Brown, managing director of London Underground: "Under our plans to modernise the Tube, we are committed to a safe railway with visible staff personally serving our passengers.

"Fairness to our staff is guaranteed - there will be no compulsory redundancies, there is a job for all staff wanting to remain with us and no one will lose pay."far