Ports-to-Plains Highway Act of 2020 This bill expands and designates certain route segments on the National Highway System. Specifically, the bill (1) designates the portion of the Heartland Expressway (relating solely to the portion from Limon, Colorado to Interstate Route I-76 in the vicinity of Brush, Colorado) and the Ports-to-Plains Corridor as future parts of the Interstate System; and (2) permits the continued operation of vehicles on any segment of the Heartland Expressway (relating solely to the portion from Limon, Colorado to I-76 in the vicinity of Brush, Colorado) and the Ports-to-Plains Corridor that is designated as a route on the Interstate System in Texas, Oklahoma, Colorado, and New Mexico, without regard to vehicle weight limitation requirements.