Department of Homeland Security officials spent $534 million in 2012 on a fleet of more than 56,000 vehicles, but they don't know whether that's too many, too few or just the right number.

The DHS fleet is the second biggest in the federal government, but the department's inspector general said in a report Tuesday that the department "does not adequately manage or have the enforcement authority over its components’ fleet operations to ensure that its motor vehicle fleet composition is right-sized."

The reason is DHS "does not have a centralized management information system" for the fleet. The department's fleet manager is also handicapped by having "to rely on multiple sources of information containing missing, unsupported, and conflicting vehicle data from the components."

One result of the lack of accurate information is that DHS has no idea which of its vehicles are under-used. The IG estimated that the department wasted as much $48 million maintaining such vehicles.

Despite all these problems, DHS officials bought 5,000 new vehicles in 2012.

The DHS was created in 2002 in response to the Sept. 11, 2001, terrorist attacks. The department combined 11 separate agencies under its authority, including U.S. Customs and Border Protection, the Transportation Security Administration and U.S. Immigration and Customs Enforcement.

Those three agencies alone operate more than 42,000 of the DHS vehicles.

The IG noted that all federal departments and agencies are required to have fleet management plans.

The General Services Administration also operates a government-wide digital information system that is meant to track costs, mileage and fuel use for all federally owned vehicles.

Read the full report here.

Mark Tapscott is executive editor of the Washington Examiner.