To amend part A of title II of the Clean Air Act to exclude trailers and other vehicles that rely on a connection to a self-propelled vehicle from the definition of a motor vehicle.

Transportation and Trailer Modernization Act of 2017 This bill amends the Clean Air Act to revise the definition of a motor vehicle to exclude trailers and vehicles reliant on a connection to a self-propelled vehicle for power. (The Environmental Protection Agency set emissions standards for trailers as a part of motor vehicle emissions regulations. The regulations as applied to trailers were stayed by a federal court on October 27, 2017.)