[Talk-us] proposed first principles for United States road tagging

[McGuire, Matthew]

I see three dimensions of road classification at play here.

1) System
2) Function
3) Observed Character

System is the easy one. That is the road system(s) that that the road belongs to especially for signage, but also for road funding channels, and maintenance responsibility.  And I agree that in practice, Census Feature Class Codes have been used (incorrectly) to identify the system to which a road belongs.

Function describes the role a road plays in a road system and the types of trips (volume and length) it supports based on travel demand and trip generation. This is what the Highway Functional Classification System is designed for. It is used by Metropolitan Planning Organizations to distribute transportation funding.

A road's Observed Character is what kind of road it appears to be to a person on the road. For general purpose maps, using observed character to classify the roads intends to match a person expectations to what they see on the ground. Character is highly correlated with function, but is not the same.

I think Observed Character is what OSM is trying to achieve with the highway tag. I think this because the OSM tag descriptions for highways have photos and describe how the road looks, and you cannot determine system or function from a photograph.  I also think it is what the Census Feature Class Code definitions describe.

I would like to see all three dimensions.

Matt



-----Original Message-----
From: David ``Smith'' [mailto:vidthekid at gmail.com]
Sent: Thursday, March 04, 2010 9:33 AM
To: McGuire, Matthew
Cc: Nathan Edgars II; talk-us at openstreetmap.org
Subject: Re: [Talk-us] proposed first principles for United States road tagging

On Wed, Mar 3, 2010 at 10:45 AM, McGuire, Matthew
<Matt.McGuire at metc.state.mn.us> wrote:
> The US Census Feature Class Code has descriptions of most types types of roads.
> This would at least tie it to an existing US standard.
>
> http://www.census.gov/geo/www/tiger/appendxe.asc
>
> This designation exists in many OSM roads tagged with TIGER:CFCC. However most roads could definitely use some refinement. We could strip the TIGER from the tag to just cfcc then refine it from there.

The original TIGER import did in fact use CFCCs to determine highway
class.  It produced values of motorway, motorway_link, primary,
secondary, and residential.  We've been refining that for 3 years now.
 The problem is, this comes from the Census Bureau.  They really don't
care about a road's functional importance.  There are CFCCs for many
other things besides roads.  And the few CFCCs assigned for road
features are essentially based on whether the road is an Interstate, a
US route, or a State Route, which doesn't correlate well with a road's
functional classification.

What's more useful is the Highway Functional Classification System.
The name sounds like what we want to do.  And it's from the Federal
Highway Administration, so they actually care about roads.  I've also
put forward guidelines for translating HFCS to OSM.
<http://wiki.openstreetmap.org/wiki/Talk:United_States_roads_tagging#Discussion>
(Sort of buried in a wall of text.  I should probably repost those
guidelines in my userspace.)

--
David "Smith"
a.k.a. Vid the Kid
a.k.a. Bír'd'in

Does this font make me look fat?