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

[Alan Mintz]

At 2010-03-04 09:38, McGuire, Matthew wrote:
>...
>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 disagree. Even if this is what was intended, it's certainly less useful 
than the others. When I zoom out a certain amount, what I want to see is 
the local (aka residential in OSM) roads disappear. Further out still, I 
want to see the tertiary roads disappear, etc. This is what's useful when 
trying to map a route through an unknown area - you want to stick to the 
main roads that get you there with better road conditions, fewer 
intersections, etc.

As an example, in this area: 
http://www.openstreetmap.org/?lat=34.426&lon=-117.664&zoom=11&layers=B000FTF 
, 2-land paved roads are few and far between, making them important 
tertiary or secondary connections. A road with the same characteristics in 
the city would be unclassified, as there are much better roads. It's all 
relative to the area, which is why I don't think it's reasonable to 
classify by any objective characteristics - you have to know or survey the 
area in order to know how to classify them. Perhaps some people with a lot 
of experience may be able to do this from satellite imagery.

I believe this closely matches what I see in transportation sections of a 
city's general plan. I think it's useful to use these as guidelines when 
classifying roads. Many cities/counties of any reasonable size make these 
available on their website. They usually have:

- freeway, expressway, etc. = OSM motorway or trunk
- primary arterial = OSM primary
- secondary arterial = OSM secondary
- minor arterial and/or collector = OSM tertiary
- local = OSM residential or unclassified

--
Alan Mintz <Alan_Mintz+OSM at Earthlink.net>