Tube: Underground rail service in London affected by strikes

A second 24-hour Tube strike in a week is causing lots of disruption in London.

Around 10,000 Underground workers haven't gone to work because of a dispute over pensions and work conditions.

It's meant that most of the Tube lines in London have been suspended for the day, meaning people have to find other ways to get to work or school.

The same thing happened on Tuesday, causing buses to be overcrowded and traffic to be gridlocked.

According to government figures, more than two million people use the London Underground every single day.

At peak times, there are more than 543 trains whizzing around the Capital.

Transport For London has advised Londoners to work from home wherever possible.

A strike is when a group of workers agree to stop working.

They do this when they want to protest against something they think is unfair where they work.

Strikes sometimes happen because workers want to force politicians or company bosses to listen to what they want.

Workers go on strike for lots of reasons. They might want to get improvements where they work, get more money, have shorter working days or stop their wages going down.

The workers are represented by something called a trade union.

A trade union is an association of workers that wants to make things better in their workplace.

They speak for their members on all important parts of their job, like wages and working hours.

By joining together, a trade union can find it easier to get the result they want than individual workers fighting separately.