Zipcar is a for-profit, membership-based carsharing company providing automobile rental to its members, billable by the hour or day. Zipcar was founded in 2000 by Cambridge, Massachusetts residents Robin Chase and Antje Danielson. On October 31, 2007 Zipcar merged with rival Flexcar. By 2009 Zipcar has become the worlds largest car-sharing service, sharing 6,000 vehicles among 275,000 drivers in 49 U.S. cities, Vancouver, Toronto, and London, representing almost half of all car-sharers worldwide. On April 1, 2010, Zipcar bought London-based car-sharing firm Streetcar in its latest bid to expand across Europe.