Commuters are facing a day of disruption after a strike shut down the London Underground system for a second time this summer.

Unions walked off the job amid a dispute about how to implement a new 24-hour service on weekends. Unions argue work-life balance issues haven't been addressed and that management should hire more people to cover extra shifts. Transport officials say they've offered a salary increase and bonuses to compensate for the changes.

Stations on the subway, known as the Tube, will be closed all day Thursday. Extra buses will run.

Transport officials are usually able to keep a few lines running during Tube strikes. But drivers have been united in staying off the job in recent strikes, forcing management to shut down the system altogether.