Zipcar, recently acquired by Avis, offers “wheels when you want them.” Photo courtesy of Zipcar.

They may not be college students, but the CEOs of these two car sharing companies seem to understand this younger generation's needs. Photo via ZIPCAR, INC.

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p>With population and urbanization rates growing, and motorization not showing any signs of slowing down, we need a new option for personal mobility. The current size and rigidness of cars leave little room for future urban growth and threaten the health of cities.

Low-carbon, affordable and convenient, Zipcar and other car-sharing programs are gaining popularity with Millennials. Photo by tedeytan.

Are you watching your friends make weekend plans through your Facebook news feed? Are you afraid you’re going to miss out on the action? Well, don’t worry because you’ll never miss a weekend of fun with Zipcar’s new Facebook application!

The number of gas stations in Manhattan, New York has decreased from 58 to 41 in the past two years. Photo by realname.

Cycling in the countryside has become an increasingly popular respite from Chinese city life. Photo by David Woo.

Zipcar’s moto, “Wheels when you want them,” resonated with Baltimore residents, leading to an 11 percent increase in public transport use. Photo by Ian Collins.

After 12 months of operation, London’s bikesharing outfit Barclays Cycle Hire boasts roughly 6 million logged bike trips.Photo by Donald Macleod.

New Delhi's Kalka Mail train derailed on Sunday, killing more than 60 passengers. Photo by Jag Pee.