(1) Under RCW 70.107.030(5) of the Noise Control Act of 1974 (chapter 183, Laws of 1974), the legislature directed the department of ecology, in exercising rule-making authority to give first priority to the adoption of motor vehicle noise performance standards. The purpose of this chapter is to carry out that legislative directive through the adoption of noise emission standards for new motor vehicles and noise emission standards for the operation of motor vehicles on public highways.

(2) Local needs. The standards established in this chapter provide several methods of evaluating motor vehicle noise levels. Nothing in these rules is meant to require enforcement agencies or local governments to adopt or use every standard in this chapter to determine a violation. Specific local needs shall dictate the standard(s) which may be adopted or used.