A sign informs travelers that Oxford Circus Tube station is closed on Thursday, July 9. Millions of Londoners were forced to find alternative ways to travel Thursday as the UK capital's Underground network was in the grip of what may be its biggest strike in more than a decade. Paco Anselmi/PA Wire/AP
Workers from an outside agency give people travel advice by the closed entrance doors of the Waterloo Underground train station in London on July 9. Matt Dunham/AP
People walk across the Millennium Bridge in London on July 9. Some 4 million journeys are typically made on the Underground each day, so when the system is down, the city comes close to grinding to a halt. Matt Dunham/AP
A commuter rides a bike through traffic in London on July 9. Commuters and tourists had to find their way to their destinations by bus, train, bicycle, taxi or on foot. BEN STANSALL/AFP/Getty Images
Commuters ride a packed bus. People have been urged to travel outside peak hours.
A man unloads bicycles to resupply a city bike-sharing station in London. Matt Dunham/AP
Early morning commuters form lines to board buses at Victoria Station. NIKLAS HALLE'N/AFP/Getty Images
People squeeze onto a bus on July 9. BEN STANSALL/AFP/Getty Images