Tex. Transportation Code § 545.365: SPEED LIMIT EXCEPTION FOR EMERGENCIES; MUNICIPAL REGULATION.

(a) The regulation of the speed of a vehicle under this subchapter does not apply to:

(1) an authorized emergency vehicle responding to a call;

(2) a police patrol; or

(3) a physician or ambulance responding to an emergency call.

(b) A municipality by ordinance may regulate the speed of:

(1) an ambulance;

(2) an emergency medical services vehicle; or

(3) an authorized vehicle operated by a blood or tissue bank.

Acts 1995, 74th Leg., ch. 165, Sec. 1, eff. Sept. 1, 1995.