Call a Bike is a dockless bike hire system run by Deutsche Bahn (DB) in several German cities. Developed in 1998 and in operation since 2000, Call a Bike uses a system of authentication codes to automatically lock and unlock bikes.

Availability may be differentiated between cities providing full area coverage, and those only offering bikes at the respective Hauptbahnhof. Full citywide coverage is provided in some of the larger cities such as Berlin, Frankfurt, Hamburg, Cologne, Darmstadt, Lüneburg, Munich and Stuttgart. The city of Karlsruhe used to have a citywide system from 2007 until 2013.^{[citation needed]}

The system uses an electronic wheel lock and a cable lock, all controlled by embedded microcontroller with touchscreen LC display. A set of 1024 pregenerated lock/unlock codes are unique to each bike and stored in memory.^[1] To find the bikes one has to search at the cross roads in the central areas of the towns or use location-based services^[2] on smartphones to find them. Customer calls the telephone number given on the bike or use the official Call a Bike app, available for iOS, Android, Windows Phone and BlackBerry, to locate a bike and receive the opening code.^[3]

• Transport in Germany
• Outline of cycling

Media related to Call a Bike at Wikimedia Commons

• Official website (German, English)