If you live in a city and own a car but drive it less than 500 miles a month, you are a candidate for car sharing.

Suited for urban populations, car sharing is an alternative to owning or leasing a car. Entrepreneurs and car manufacturers are offering new approaches to car sharing that provide new incentives for getting rid of your car, or even making some money off vehicles you rarely use.

Car sharing services use a bundle of new technologies including smart cards instead of keys, mobile apps for registration and smart tracking devices for security.

BMW's one-way car sharing

Leave it to the makers of BMW to find a way to eliminate one of the most common complaints about car sharing: the inconvenience of pickup and drop-off locations. At the NYC Big Apps show last week, the carmaker unveiled its DriveNow program, a one-way car sharing service consisting of a fleet of BMWs and Mini Coopers that can be driven on a whim and left wherever.

BMW's DriveNow program is the first car sharing service to offer random vehicle locations, a freedom that would not have been possible without the integration of today's smartphones, GPS and location-based apps.

Participants use the DriveNow app on their mobile phones to locate the nearest available vehicle. If luck is on their side, there's a DriveNow car within a city block.

"Or if you see a DriveNow car on the street, see if it's free and jump in that instant," a BMW promotional video suggests.

Motorists may register for the service with their driver's licenses. The system is “keyless”: a conventional car key is not necessary. Unlike car sharing services that issue smart cards, DriveNow applies an electronic sticker to a participant's driver's license, turning the license itself into a key.

Once inside the car, the driver punches in a PIN code from the service in a small device located near the steering column, which allows the engine to be started. DriveNow charges 29 cents a minute, gas is included, and public parking within the city is free.

For now, DriveNow is limited to the city streets of Munich, but the company plans to roll out service internationally over the next several years.

America's standard: Zipcar

America is no stranger to car sharing, especially in its big cities. Car sharing services began in the mid-1980s, gained popularity during the recent recession and seem poised to surge again with soaring gas prices.

Zipcar, with 550,000 members, is the largest car sharing service in the world and represents 80 percent of the car sharing market in the United States. The company issues its members RFID (radio frequency identification) smart cards for vehicle access and offers reservations through mobile apps, including one designed specifically for the iPhone and two-way texting for reminders and instant rental extensions.

Neighbor-to-neighbor car sharing

A community car sharing service recently hit the streets of San Francisco after a test run in Boston. RelayRides took the idea of Zipcar a bit further: Rather than rent out cars from its own managed fleet, it set up a system for borrowing cars from individual car owners whose vehicles were idle for much of the day. The owner specifies when the car is available and the hourly rate. Renters reserve the car online and use a RelayRides smart card for access.

The big benefit to the renter is a ride that is typically a lot closer, and the car owner gets paid. Think of it as a neighborhood car co-op.

RelayRide's 28-year-old founder, Shelby Clark, is eager to expand the service. In the company's neighborly spirit, individuals have been invited to start a program in their towns by recruiting four car owners and 50 borrowers within a one-mile radius. Once this threshold is met, Relay Ride will step in to set up the cars with the company's in-vehicle technology and a $1 million insurance policy for the group.

Is car sharing right for you?

Car sharing may be the tipping point for people who are thinking of giving up their cars for good, whether to save money or save the environment or both. A long-term study by the University of Berkeley found that 30 percent of households who joined City CarShare car sharing sold their own car, and 66 percent of those who intended to purchase a new car changed their minds after joining the service.

Along with their driving frequency and schedule, candidates for giving up their own cars should consider the availability of nearby public transportation and alternate methods of transportation, such as a bike, as well as their current car expenditures. Under the right circumstances, sharing a car can save ― and possibly earn ― money.

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