A bill to amend the Clean Air Act to provide for more effective motor vehicle emission controls at high altitudes, and for other purposes.

Provides that regulations under the Clean Air Act shall require that any vehicle or engine to which emission standards under such Act apply shall comply with such emission standards at that altitude, up to seven thousand feet above mean sea level, at which such vehicle or engine is sold to the ultimate purchaser.

Authorizes State agencies to prescribe regulations under the Clean Air Act authorizing specific modifications by the manufacturer or dealer of any motor vehicle emission control system if such modifications are within reasonable cost limits and are necessary to assure that such system functions in compliance with the provisions of such Act under normal driving conditions in the appropriate State, including high altitude conditions.

Authorizes the appropriation of up to $750,000 through June 30, 1975, for the purpose of studying the problems of motor vehicle emissions peculiar to urban areas located more than four thousand five hundred feet above mean sea level.