Just a heads-up to mappers in the United States: we’re starting to tag highways with
relation:route (see the tagging guide). Entire highways will be joined with one (two?) relations. Because Interstate highways and U.S. Routes cross state lines, we’re trying to coordinate our efforts with two wiki pages:
One of the driving forces for using relations is that we can cleanly handle concurrencies. Eventually, we can also look forward to custom highway shields like we’re used to seeing on virtually all other maps. Looks like it hasn’t been mentioned on Planet OSM yet, but here’s a nice demo of the shields being rendered.