WASHINGTON – The U.S. Government owns 642,233 vehicles. Operating those vehicles — maintenance, leases, and fuel — cost $3.4 billion last year, according General Services Administration data obtained and analyzed by The Associated Press.

The government owns or leases sedans, SUVs, trucks, limousines, and ambulances for more than three dozen agencies, the U.S. military, and the Postal Service. But according to the Washington-based Citizens Against Government Waste, saving taxpayer dollars should be a priority.

The Department of Housing and Urban Development (HUD) admits problems with its fleet of about 450 vehicles. According to an AP analysis, fleet costs at HUD have soared nearly 70 percent since 2004, to more than $2.1 million last year. But during the same period, the agency trimmed its fleet and overall fuel consumption. While gas prices have increased since 2004, the period AP analyzed came well before today’s record-high prices.

HUD has begun a thorough review of its vehicles, how they are being used, and whether each is justified.

The latest report available from the Government Accountability Office, from 2004, looked at the fleets of five departments including Veterans Affairs, Homeland Security, and the Navy. It found a number of instances where agencies were keeping vehicles they didn’t need. Ditching those cars, the report said, could save the government millions of dollars.

The Interior Department was another agency singled out for wasteful spending. In a 2004 report, the agency’s inspector general found a significant portion of department vehicles weren’t being driven much. Eliminating them could save $34 million a year.

Interior cut more than 600 vehicles before the report was released, but its overall fleet has increased by more than 1,500 vehicles since then, according to an AP analysis of GSA data. Interior ranks fourth among civilian agencies in the size of its fleet, but it spends the most money — more than $241 million last year on vehicles, maintenance, and fuel. Agriculture has the largest fleet but spends far less, about $150 million.

Only a handful of agencies said they have conducted annual audits to ensure their fleets are the right size. The Department of Homeland Security said it hasn’t conducted a department-wide audit since the agency was created five years ago. The agency said it is “working toward that end” but doesn’t yet have the resources to analyze its 41,000-vehicle fleet.

At Veterans Affairs, an audit last year by the inspector general’s office found potential savings of about $83,000 for underutilized vehicles, but it looked at only three VA medical centers. The VA has more than 150 centers, raising the prospect of additional underused cars and more savings.

In the case of a Cleveland VA medical center, a government-leased vehicle was driven only 16 times in nearly a year; another was driven only twice in the three months after it arrived. One sedan at the center was missing and apparently hadn’t been seen in months.

All agencies are supposed to report their annual fleet numbers to the General Services Administration. However, the cost and inventory estimates in the GSA’s annual report do not include Congress, which isn’t required to report to GSA on its fleet, according to AP.