Ticket entrance machines are seen behind metal gates at the closed entrance to Marylebone tube station in London, Thursday, Aug. 6, 2015. 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. (AP Photo/Kirsty Wigglesworth)