Health & Saf. Code, § 40910

It is the intent of the Legislature in enacting this chapter that districts shall endeavor to achieve and maintain state ambient air quality standards for ozone, carbon monoxide, sulfur dioxide, and nitrogen dioxide by the earliest practicable date. In developing attainment plans and regulations to achieve this objective, districts shall consider the full spectrum of emission sources and focus particular attention on reducing the emissions from transportation and areawide emission sources. Districts shall also consider the cost-effectiveness of their air quality programs, rules, regulations, and enforcement practices in addition to other relevant factors, and shall strive to achieve the most efficient methods of air pollution control. However, priority shall be placed upon expeditious progress toward the goal of healthful air. It is also the intent of the Legislature that redundant work shall be avoided.