Car2go just feels like the future. Swipe an RFID card in front of the flashing display on the giant windshield of this tiny two-seater – with it's smiling grill and steel roll cage – and, after a minute delay, the car beeps, the doors unlock, and it's yours.

In Austin, San Diego, Washington, D.C, Miami, and now Portland, Oregon, there's a breakthrough car-sharing system taking over the city. Car2go is more an alternative public transportation option than it is a car rental system. For one, it works closely in conjunction with its host city, negotiating parking spaces and use zones. There's also no central garage or office, with the cars tracked by GPS and the whereabouts of available cars published through an iPhone app or the website. When you're finished driving a vehicle, park (anywhere in the city), swipe your card, and walk away – this vehicle is no longer your problem. "This is the next generation of car sharing," boasts Nicholas Cole, president and CEO of car2go. "Cities are faced with traffic congestion, emissions concerns, and rising costs in public transit," he says, and this car-sharing program "complements existing public transit." For those times when the bus or train is down or you're taking a circuitous, off-line route – for a few errands or to pick up a friend – it's complementary role is obvious.

Of course, you will need to sign up for a membership – a license, a credit card, and a one-time $35 fee are all that's required – and you can use the system in any city in the U.S. once you get your card in the mail. Car usage is on the clock for $0.35 per minute, including insurance, with a maximum of $12.99 per hour or $65.99 per day, with no fueling required (though after you drive 150 miles, you have to pay $0.45 cents per mile, making this mostly an in-town solution). The cars used are all gas-powered Mercedes Smart ForTwos, with the notable exception of the San Diego fleet, which is all-electric. These are the perfect vehicles for such a system: They're easy to park and find (these little guys do stand out); they're safe, packing a whopping eight airbags; and they were more than capable of hauling on the intercity byways like Route 30 in Portland on our way to a morning run at Wildwood Trail. The car is small and tracked by GPS, but as we sped toward the largest forested city park in the U.S. from the asphalt heart of downtown, it felt a lot like freedom.

More information: Besides its availability in five U.S. cities, car2go also runs systems in Canada (Calgary, Toronto, and Vancouver), Germany (Berlin, Düsseldorf, Hamburg, Cologne, Ulm), the Netherlands (Amsterdam), France (Lyon), Austria (Vienna), and the United Kingdom (Birmingham). Separate memberships are required for each country outside of the U.S. [car2go.com]