A new car-sharing company is pairing car owners with individuals who need a short-term rental car, according to Mother Nature Network. RelayRides is hoping to turn underused vehicles in the U.S. into a revenue stream for the car owner and RelayRides.

RelayRides will soon be launching its service in Baltimore, Md.

Although ZipCar is probably the most well-recognized car-sharing service in the United States, RelayRides is a new company that is also touting the environmental benefits of car sharing.

The company states that a shared car replaces 14 to 18 cars on the road, causing less pollution. To participate in the program, RelayRides requires drivers to be at least 21 years of age, with exceptions for drivers as young as 18 with excellent driving records who have been licensed to drive for at least two years, and who are insured.

RelayRides charges no age-related premiums. The company’s pricing plan includes hourly and daily rates, at $6 per hour for an economy vehicle that is model year 2003 or older. Specialty vehicles that are model year 2007 or newer top out at $12 per hour.

The company also charges a separate fee for excess miles. Anything over 20 miles per reservation hour or 160 miles per day is excess, and the company doesn’t impose a fixed cap on rental length. A car is available for as long as the participating owner designates. RelayRides talks about the potential profit that owners can receive by participating in the program.

Owners of a brand new 2010 luxury car that rent out a vehicle for 20 hours per week could earn about $8,000 in a year. Income potential does vary based on the year of the vehicle, the type of vehicle and the condition of the car.

RelayRides maintains an auto insurance policy beyond what is carried by the owner in case a driver has an accident while driving a RelayRides vehicle. This policy will pay for repairs or replacement costs and provide the owner with a rental car during the repair period. Consumers who don’t live in Baltimore can sign up for the car-sharing service on the RelayRides Web site.