Decatur, AL Noise Ordinances: Vehicle Noise (2026)

Section 22-47 of the Decatur City Code, adopted by Ordinance No. 14-4201 on October 20, 2014, bans engine brake noise on city streets. An engine compression brake is any device that uses compression or rapid release of compressed air in the cylinders of diesel engines to slow or retard vehicle speed. Subsection (b) makes it unlawful for the operator of a motor vehicle to engage, allow to be engaged, operate or use one while the vehicle is on any public roadway within the corporate limits of Decatur.

Three exemptions apply. The first is a public safety vehicle, meaning any vehicle operated by the Decatur Fire Department or Decatur Police Department or any other vehicle within the definition of authorized emergency vehicles in Code of Ala. 1975, § 32-1-1.1. The second is a vehicle in an emergency not caused by the operator's own use of the brake, where the operator reasonably believes the brake is necessary to avoid or mitigate an accident or collision. The third is a vehicle equipped with a noise baffling device.

A noise baffling device is defined as a properly functioning muffler or engine exhaust silencer that eliminates the offensive and disturbing noise caused by use of engine compression brakes. It must reduce the noise to levels meeting vehicle noise emission standards set or authorized by the Noise Control Act (42 U.S.C. § 4901 et seq.) and the United States Environmental Agency, and comply with all other federal, state or local vehicle noise laws. Proof is practical: a law enforcement officer or other competent witness can give opinion evidence based on personal observation on whether the vehicle had a properly functioning noise baffling device.

The city is authorized, but not required, to post traffic control devices to supplement enforcement. The section is severable, so an invalid provision does not void the rest. The city's separate truck-route rule in § 22-46 is a routing ordinance, not a noise rule.