DALLAS- Not all state vehicles are used on a regular basis, despite the Texas Legislature's demand that they be used regularly, according to a WFAA-TV News 8 investigation.

A News 8 investigation found large agencies such as the Texas Department of Transportation (TxDOT) don't follow the rules, and the state agency in charge of managing all vehicles has struggled to enforce its own policies.

In the Dallas area, in 2008, the TxDOT Dallas District office had nearly 400 pickup trucks that are of part of the state fleet of lighter-duty vehicles. But an analysis by News 8 found almost 20 percent of them were driven fewer than 11,000 miles, which is required under state law.

To save money, under-used vehicles are supposed to be re-assigned within an agency - or sold.

"I think we've taken measure to try to evaluate what our practices are and what our procedures are, and to be responsive to the legislature," said TxDOT spokeswoman Cynthia Northrop White.

Representative Linda Harper Brown, a member of the House Transportation Committee, said the agency needs to do a better job managing its fleet. She's angry about a memo from the TxDOT office in Houston that says: "In order to meet this [11,000 mile] goal, you need to drive your vehicle an average of 916 miles per month."

"Instead of trying to consolidate and lessen, or reduce the number of vehicles that an agency has, what they're doing is have employees drive the vehicles just to put miles on them," Brown said.

In 2008, News 8 found that across the State, 325 TxDOT vehicles were under-used. Technically, they should have been re-assigned or sold.

But that same year, the state agency responsible for enforcing vehicle usage at state agencies reported that only nine TxDOT vehicles statewide were under-used.

Ron Pigott with the State Comptrollers Office told News 8 there were issues with incorrect data.

His agency assumed responsibility for the state's fleet two years ago. Prior to that, he says, the information that was meticulously recorded by tens of thousands of state employees was virtually worthless.

The Comptroller has since instituted a new software system to better track state vehicles and save taxpayer money, reported News 8.