Some possible new legislation coming.< cynical_1 >
"There are three primary transcontinental interstate highways that run completely from coast to coast (I-10, I-80, and I-90), though some federal reports count up to 10 major east-west corridors that span vast transcontinental distances across the country."
The legislation, and if none comes about, EO's, will change the system slightly. Same signs with the addition of the letters TT appearing in front of the letter I, signifying (Trump) transcontinental Interstate highways.