Some big news from one of the major pay-as-you-drive brands, Zipcar. The people at earth2tech are reporting the following:

Zipcar has bought a minority stake in car sharing startup Avancar, with an option to increase its ownership share in the Barcelona, Spain-based company during the next year, according to arelease from Zipcar on Friday. This represents the first concrete step Zipcar has revealed toward its goal of expanding beyond the U.S. and Canada since setting up a car sharing network in London, England in 2006.

This week’s investment comes more than two years after Zipcar absorbed its largest competitor: Seattle, Wash.-based Flexcar, owned by AOL co-founder Steve Case. The merger resulted in a company with 180,000 subscribers and more than 5,000 vehicles in 48 cities — three times the size of Flexcar, as the Seattle Times reported at the time. Since then, Zipcar has grown to 350,000 members and 6,500 vehicles in cities and college campuses throughout throughout 28 provinces and states in North America.

By comparison, Avancar — owned by Catalunya Carsharing – has built up a small network over its four years of existence. The company serves 3,500 customers around the Barcelona metro area, with vehicles in 39 locations. Some 20 percent of those clients are “businesses and administrations,” an area where Zipcar is trying to expand its presence (in April, Zipcarlaunched a fleet management service for enterprise customers). Like Zipcar, Avancar rolls insurance and fuel costs into the hourly rental fee, and customers unlock their reserved vehicle using a swipe card on the windshield .