Columbia subject headings:
Harvard subject headings:
Aeronautics--Environmental aspects--United States.
Airports--Environmental aspects--United States.
Boats and boating--Environmental aspects--United States.
Local transit--Environmental aspects--United States.
Railroad cars--Design and construction--Environmental aspects--United States.
Railroads--Design and construction--Environmental aspects--United States.
Shipping--Environmental aspects--United States.
Transportation, Automotive--Environmental aspects--United States.
Transportation--Environmental aspects--United States
Princeton subject headings:
Aeronautics--Environmental aspects--United States.
Airports--Environmental aspects--United States.
Boats and boating--Environmental aspects--United States.
Local transit--Environmental aspects--United States.
Railroad cars--Design and construction--Environmental aspects--United States.
Railroads--Design and construction--Environmental aspects--United States.
Shipping--Environmental aspects--United States.
Transportation, Automotive--Environmental aspects--United States.
Transportation--Environmental aspects--United States.