Affirmative defenses.
Houston Code of Ordinances § 21-303
in effectSec. 21-303. - Affirmative defenses.
The restrictions in section 21-302 of this Code do not apply to:
(1) A motor vehicle 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;
(2) A motor vehicle forced to remain motionless because of traffic conditions over which the operator has no control;
(3) The primary propulsion engine of a motor vehicle that is being used to supply heat or air conditioning necessary for passenger comfort and safety in vehicles intended for commercial or public passenger transportation, or passenger transit operations, in which case idling up to a maximum of 30 minutes is allowed;
(4) The primary propulsion engine of a motor vehicle being used to provide air conditioning or heating necessary for employee health or safety in an armored vehicle while the employee remains inside the vehicle to guard the contents while the vehicle is being loaded or unloaded;
(5) The primary propulsion engine of a motor vehicle being used to provide air conditioning or heating necessary for employee health or safety while the employee is using the vehicle to perform an essential job function related to roadway or utility construction or maintenance;
(6) The primary propulsion engine of a motor vehicle providing a power source necessary for mechanical operation, other than propulsion, and/or passenger compartment heating, or air conditioning;
(7) The primary propulsion engine of a motor vehicle being operated for maintenance or diagnostic purposes;
(8) The primary propulsion engine of a motor vehicle being operated solely to defrost a windshield;
(9) The primary propulsion engine of a motor vehicle being used as airport ground support equipment;
(10) The owner of a motor vehicle rented or leased to a person that operates the vehicle and is not employed by the owner; or
(11) The motor vehicle when idling is necessary to power a heater or air conditioner while a driver is using the vehicle's sleeper berth for a government-mandated rest period and is not within two miles of a facility offering external heating and air conditioning connections at a time when those connections are available.
(Ord. No. 2015-1086, § 2, 11-4-2015)
Source: City of Houston, Code of Ordinances and City Charter (Municode Library, library.municode.com)URL: https://library.municode.com/tx/houston/codes/code_of_ordinances?nodeId=COOR_CH21HE_ARTXREEMIDMOVE_S21-303AFDEFetched: 10/26/2026