Talk:Highway Functional Classification System

I think the following would be a better translation, fitting better with OSM’s current usage:

Possible translation from HFCS class to OSM highway tag

Rural HFCS	Urban HFCS	OSM
Interstates & other freeways	Interstates & other freeways	highway=motorway
Expressways	Expressways	highway=trunk
Other Principal Arterials		highway=primary
Minor Arterial Roads	Other Principal Arterials	highway=secondary
Collector Roads	Minor Arterial Streets	highway=tertiary
	Collector Streets	highway=unclassified
Local Roads		highway=unclassified(rural)
	Local Streets	highway=residential(urban)

--Hawke 08:40, 18 January 2010 (UTC)

The "current usage" that underuses the trunk classification seems to primarily be an artifact of unfamiliarity with the word "trunk" and an artifact of the Tiger import that marked (almost?) all roads as either motorways (interstates), secondary (state highways), or residential, mostly incorrectly. The US is the only country in which trunk is not widely used for primary rural routes, regardless of whether they are divided or "expressway", whatever that means. None of the OSM-wide guidelines or renderers treat "trunk" as a physical classification; they all assume that it is to be used for the most important non-motorway routes. Maps that treat it as a physical classification have unsightly disconnections in the network at zoom levels that only include motorway and trunk. The US standard should at least be broadly compatible with that used worldwide, which I believe precludes us from using "trunk" as a physical, rather than functional, specification. --Speight 07:43, 6 March 2010 (UTC)

My understanding of current de facto usage is for both surface expressways and major intercity highways: United States roads tagging#Trunk tag --NE2 07:51, 6 March 2010 (UTC)