The car-sharing service has proven to be a lucrative business model, and Avis is cashing in on this by buying Zipcar for $491.2 million, while aiming to capture a new type of customer and technology that will vastly expand its car rental options. Carsharing has become a very popular alternative to the usual rental service, and has thrived in the metropolitan areas and college campuses, which allows members to get a vehicle for an hour or two for short trips, running errands, that kind of thing — instead of renting for a day or using public transportation. This model of rental is growing while the traditional car rental business models have struggled in the current economy. Zipcar, was founded in 2000, has more than 760,000 members, triple what it had in 2008. Even after going public in 2011, Zipcar is just coming out of its first-ever profitable year in 2012.