Highway means any road, street, or way, whether on public or private property, open to public travel. Open to public travel means that the road section is available, except during scheduled periods, extreme weather or emergency conditions, passable by four-wheel standard passenger cars, and open to the general public for use without restrictive gates, prohibitive signs, or regulation other than restrictions based on size, weight, or class of registration. Toll plazas of public toll roads are not considered restrictive gates.
49 CFR § 390.5
Unless specifically defined elsewhere, in this subchapter: