The Ultimate Interstate System - Provides an overview of what the system could look like in the future according to the webmaster. Includes exit listings for all primary routes.
The US Highways that never were - By Robert V. Droz. Alignments for US 0, US A1A, US 39, US 47, US 88, US 100, and US 402. Also, there is a list of the US highway numbers still not used.