Tenn. Code Ann. § 4-22-102

If an entity has, as part of the entity's motor vehicle fleet, motor vehicles that have been modified from the vehicles' original construction for an educational, emergency services, or public safety use or motor vehicles that are used for emergency services or law enforcement purposes, then the entity shall provide for a reduction or displacement of at least ten percent (10%) of the current petroleum products consumed by those motor vehicles in the entity's reduction and displacement plan.