Following the lead of two of its rental car competitors, Enterprise and Hertz, both of which already offer car-sharing services, Avis announced Wednesday that is buying Zipcar for about $491 million. (Associated Press)

Following the lead of two of its rental car competitors, Enterprise and Hertz, both of which already offer car-sharing services, Avis announced Wednesday that is buying Zipcar for about $491 million. (Associated Press)