A bill to allow use of highway funds for any transportation improvements necessary to avoid air pollution dangerous to public health, and to prohibit highway projects which may create air pollution dangerous to public health.

Provides that the Secretary of Transportation, upon the joint request of a State Governor and the local governments concerned, shall withdraw his approval for any route or portion thereof designated or selected as part of the Federal-aid primary system, the Federal-aid secondary system, or the Interstate System within an urbanized area where he determines that the Administrator of the Environmental Protection Agency has certified that the air quality region which contains such urbanized area will fail to achieve, by July 1, 1975, levels of air quality in accordance with the Clean Air Act.

Provides that amounts appropriated to a State for projects on routes or portions thereof for which approval has been withdrawn in accordance with this Act shall be transferred to and added to the amounts apportioned to such State under the Federal-aid urban system for the account of the urbanized area from which the withdrawal of the routes or portions thereof was made. (Amends 23 U.S.C. 103)

Provides for emergency assistance for transportation system improvements in those air quality regions within a State which the Administrator of the Environmental Protection Agency has certified necessary will fail to achieve, by July 1, 1975, levels of air quality.

Makes ten percent of the funds appropriated for expenditure upon the Federal-aid systems available for such assistance.