WASHINGTON (AP) - Volkswagen is far from the first auto company accused of trying to game required environmental tests.

WASHINGTON (AP) Volkswagen is far from the first auto company accused of trying to game required environmental tests.

Almost since the Clean Air Act was enacted in 1970, major manufacturers of cars, trucks and heavy equipment have been busted using what regulators call "defeat devices." The cheating typically involves programing a vehicle's on-board computer to boost horsepower or fuel mileage by belching out dirtier exhaust than allowed.

Over the years, manufacturers including GM, Ford, Honda and, yes, Volkswagen, have been forced to pay hefty fines and recall vehicles after getting caught.

Critics blame a federal regulatory system that largely relies on manufacturers to "self-certify" that their vehicles meet required fuel economy and emissions standards. Complying with such regulations can add thousands of dollars to a vehicle's sticker price while diminishing driving performance.