The federal fleet of cars and trucks, the majority of which — about 200,000 vehicles– are managed for civilian agencies by the General Services Adminstration, cost GSA $430 million last year, according to a report on the fleet.

These include fuel, depreciation and maintenance costs, plus the tab to replace cars and trucks once they wear out.

It’s a lot of money. With an eye toward reducing costs, GSA announced Wednesday that it will start experimenting in November with a novel way for federal employees to get around when they’re on business: By joining the rapidly growing car-sharing economy.

Government workers at a range of agencies in the District, New York City, Boston and Chicago will now be able to hop in a ZipCar or other vehicle owned by one of three other car-sharing businesses that won federal contracts in August: Enterprise CarShare, Hertz, and Carpingo.

The pilot program is designed to give employees who need a government car for a few hours or up to a day the option of a car-share instead of a taxi ride, a rental car or a government-owned vehicle.

Car sharing, for the uninitiated, is a type of car rental that’s designed to be convenient for people who want to rent cars for short periods — a few hours — and only pay for the distance they travel and the time they use the car. Cars are usually spread around cities and suburbs in reserved spots on the street.

GSA Administrator Dan Tangherlini said in a statement that the goal of the pilot is to save money by reducing the need to buy new cars and bringing more efficiency to the government fleet.

His hope is that even at rates of $7 to $15 an hour — depending on the make, model and size of a car and the vendor –the money the government spends on car sharing will still save costs associated with keeping up the traditional fleet. And car-sharing could eventually eliminate the need to keep vehicles that are used infrequently, GSA officials said.

A GSA spokeswoman said the agency hasn’t yet established a solid metric for savings. But the pilot should help officials figure out how much the government could save in the long term.

The pilots are expected to start by the end of November. GSA will work with federal offices in the four test cities to identify agencies that are most likely to use car-sharing.