Road Numbering Systems
Many details from nearly every country.
CatSynth.com - Highways
Contains commentary and information about various routes.
Me and the Roads
Java game involving road-building.
A guide for conditions of facilities as rated by website visitors.
Trans Global Highway
Proposal by a private citizen to construct a global railroad and vehicle highway around the world including a tunnel under the Bering Strait from the United States to Russia, from Sakhalin in Russia to Hokkaido in Japan, and from Spain to Africa. Includes maps.
Manages and develops urban toll road networks in Australia and the USA.
Worldwide Transportation Library
Covers North America (primarily the Western U.S.), Asia and western Europe.