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.”