Compression brakes.
Seattle Mun. Code § 11.84.070
in effect11.84.070 - Compression brakes.
A. 1.
This subsection applies to all motor vehicles with a declared gross weight in excess of 10,000 pounds operated on a street or alley and equipped with engine compression brake devices. An engine compression brake device is any device that uses the engine and transmission to impede the forward motion of the motor vehicle by compression of the engine.
2. The driver of a motor vehicle equipped with a device that uses the compression of the motor vehicle engine shall not use the device unless:
a. The motor vehicle is equipped with an operational muffler and exhaust system to prevent excess noise. The muffler and exhaust system must maintain the noise level at eighty three (83) decibels or less for motor vehicles manufactured after January 1, 1979, and eighty (80) decibels or less for motor vehicles manufactured after January 1, 1988; or
b. The driver reasonably believes that an emergency exists which requires the use of the device to protect against an immediate threat to the physical safety of the driver or others, protect against immediate threat of damage to property, or effectively reduce the speed of the motor vehicle using the manufacturer's motor vehicle braking system when declining from an elevated roadway.
3. The monetary penalty for violating this subsection is two hundred fifty dollars ($250.00) for the first violation, five hundred dollars ($500.00) for the second violation, and (c) seven hundred fifty dollars ($750.00) for each violation thereafter. (RCW 46.37.395)
B. 1.
In addition to the restriction imposed by subsection A of this section, no person shall use an engine compression brake device while operating a motor vehicle on any street where signs prohibit the use of compression brakes, except where an immediate stoppage or slowing of the vehicle is necessary in order to prevent injury to persons or damage to property or to remedy an injury that has already occurred, and that friction brakes are either not available or would not have been as effective in bringing the vehicle to a stop or slowing it.
2. This subsection shall not apply to vehicles of a municipal fire department, whether or not responding to an emergency, participating in an exercise in emergency management, or rendering assistance under a mutual aid pact.
(Ord. 122742, § 33, 2008.)
Source: City of Seattle, Seattle Municipal Code and City Charter (Municode Library, library.municode.com)URL: https://library.municode.com/wa/seattle/codes/municipal_code?nodeId=TIT11VETR_SUBTITLE_ITRCO_PT8EQRE_CH11.84BRMIEQ_11.84.070COBRFetched: 11/1/2026