Tennessee cities may regulate, but not prohibit, the use of engine compression braking devices by ordinance provided that the ordinance conforms to Interstate Motor Carriers Noise Emission Standards as outlined in 49 C.F.R. 325 et seq.
T.C.A. § 55-7-117 states that truck tractors and semi-trailers, as defined in T.C.A. § 55-8-101, shall not use an engine compression braking device unless the device is equipped with an operational, approved muffler.
Federal testing procedures for measuring allowable decibel levels of truck tractor and semi-trailers require certified equipment, testing sites, testing procedures, and inspectors. The testing standards are very complex, and most cities do not have the ability to administer such tests. Cities experiencing problems with noise pollution from engine compression devices are advised to use a visual muffler inspection procedure to reduce the noise level from engine compression braking systems.
MTAS recommends that cities desiring to enforce engine compression braking device standards require that truck tractors and semi-trailers comply with the approved muffler requirements of T.C.A. § 55-7-117. Cities may request appropriate highway notice signs from the Tennessee Department of Transportation.