Texas Health and Safety Code - HEALTH & SAFETY § 382.0191. Idling of Motor Vehicle

(a) In this section, “idling” means allowing an engine to run while the motor vehicle is not engaged in forward or reverse motion.

(b) The commission may not prohibit or limit the idling of any motor vehicle with a gross vehicle weight rating greater than 8,500 pounds that is equipped with a 2008 or subsequent model year heavy-duty diesel engine or liquefied or compressed natural gas engine that has been certified by the United States Environmental Protection Agency or another state environmental agency to emit no more than 30 grams of nitrogen oxides emissions per hour when idling.