A. No motor vehicle shall be purchased, leased, or subject to a contract rental with public funds by the Commonwealth or by any officer or employee on behalf of the Commonwealth without the prior written approval of the Director. No lease or contract rental shall be approved by the Director except upon demonstration that the cost of such lease or contract rental plus operating costs of the vehicle shall be less than comparable costs for a vehicle owned by the Commonwealth. Notwithstanding the provisions of this subsection, the Virginia Department of Transportation shall be exempted from the approval of purchase, lease, or contract rental of motor vehicles used directly in carrying out its maintenance, operations, and construction programs.