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The report challenges claims by the American Automobile Manufacturers Association (AAMA) that modern cars are 90-96% cleaner than 1960s precontrol cars. It finds that real-world emissions are significantly higher than regulatory standards due to equipment malfunction and 'off-cycle' driving. Furthermore, a 2.7-fold increase in total vehicle miles traveled and a shift toward light trucks—which have less stringent standards—have offset per-vehicle gains. Consequently, while hydrocarbons decreased, nitrogen oxide emissions for the total passenger fleet actually increased by over 20% between 1965 and 1995. The author concludes that passenger vehicles remain a primary source of carbon monoxide and smog-forming pollutants, necessitating a shift toward intrinsically-clean vehicle technologies.