DIAMOND BAR, Calif. --- A federal judge has signed an agreement ending more than seven years of litigation that will allow the South Coast Air Quality Management District to continue enforcing its clean fleet rules.

"This is a victory for clean air in Southern California," said William A. Burke, AQMD's governing board chairman.  "It means that fleets of transit buses, school buses, refuse trucks and certain other fleets will continue to phase out their dirty diesel vehicles and replace them with clean-fueled models."

The agreement approved in federal court will effectively end a lawsuit jointly filed on Aug. 31, 2000 by the Engine Manufacturers Association and the Western States Petroleum Association claiming that the agency's clean fleet rules were pre-empted by the federal Clean Air Act.  The agreement was approved in the Central Division of U.S. District Court by Judge Florence-Marie Cooper, who twice ruled in favor of AQMD in the case.

AQMD's clean fleet rules, adopted in 2000 and 2001, apply to fleets of transit buses, school buses, refuse trucks, street sweepers, city-owned utility trucks, airport shuttles and taxi fleets in the agency's four-county region.  The rules require fleet operators of 15 or more vehicles to purchase a clean-fueled vehicle, such as one operating on natural gas, when they replace or add a vehicle to their fleet.

The effect of the agreement is that AQMD's clean fleet rules will continue to apply to all publicly owned fleets, such as school buses operated by public school districts.  In addition, the fleet rules will continue to apply to privately owned fleets under contract to a public entity, such as private school bus companies that provide services to public school districts.

The rules will not apply to fleets that are privately owned and not under contract to a public entity or to fleets operated by the federal government.

AQMD adopted its fleet rules following a 1999 landmark study of toxic air pollution.  It found that most of the cancer risk from air pollution was due to diesel exhaust.

The Engine Manufacturers Association (a trade group of diesel engine makers) and the Western States Petroleum Association originally filed its lawsuit challenging AQMD's fleet rules in U.S. District Court in Los Angeles.  AQMD prevailed in both the district court in 2001 and in the Ninth Circuit Court of Appeals in 2002.  The plaintiffs succeeded in petitioning the Supreme Court of the United States to hear the case in 2004.

The Supreme Court reversed the lower court's decision but sent the case back to district court to determine whether the fleet rules were not pre-empted under various legal doctrines.

In 2005 Judge Cooper again ruled in AQMD's favor.  Plaintiffs appealed once more to the Ninth Circuit Court of Appeals, which partly affirmed and partly vacated the lower court's ruling.  The court of appeals sent the case back to the district court.  Instead of pursuing further litigation, all parties proposed an agreement that was approved by the district court.

AQMD is the air pollution control agency for Orange County and major portions of Los Angeles, San Bernardino and Riverside counties.