Yakima County does not have an ordinance in place against compression brake use, and therefore such signs are not installed along Yakima County roadways. Some points in favor of compression brakes use:
- Compression brakes are a safety feature and we do not wish to limit or regulate a drivers ability to operate their vehicle as legally configured to operate as safely as possible.
- Medium and Heavy trucks built after 1979 are limited to 83 dBa and after 1988, 80 dBa by Federal regulation. While this isn’t necessarily quiet, it is a reasonable noise level similar to a vacuum cleaner, garbage disposal, or bus.
- Modern trucks have automatic transmissions and in talking to our County truck drivers we have found they prefer to use compression braking for speed control even more in automatics than when driving a manual transmission truck – especially on a sustained grades.
- Modern trucks have fairly quiet compression brakes.
Certainly, there are non-complying vehicles in terms of their noise levels. These non-complying brakes are loud and disruptive, but enforcement is very difficult, requiring direct observation by an officer and the ability to accurately discern whether or not they are in compliance. Often non-complying brakes are found on older farm trucks. WAC 173-62-060 specifies enforcement criteria and states the “Measurements shall be made with a sound level meter meeting Type 1, S1A, 2 or S2A requirements as specified in the American National Standards Specifications for Sound Level Meters S1.4-1971 as required under measurement procedures established in chapter 204-56 WAC, "procedures for measuring motor vehicle sound levels." WAC 204-56 was repealed circa 1997/1998. We believe this WAC was repealed because it presented rigorous methodology that was more appropriate in a controlled setting than actual field conditions, and we are unaware of any replacement WAC. So in order to enforce, Law Enforcement formerly needed special tools and training and effort. Currently, we are unaware of specifications for level and how to determine it other than reliance on the Federal regulation - CFR 205.54-1,2 - also very rigorous and specialized in terms of measurement. This is a difficult predicament for law enforcement for enforcement which is a significant contributor to why the county does not have an ordinance in place.
WSDOT South Central Region shares similar sentiments about compression brakes, and does not post signs prohibiting their use on state roads, excepting within city limits where they are prohibited, and even then WSDOT only posts these signs when requested by the local agency.