[OSM-Talk-ZA] Tagging

[Paul van Helden]

Hi All,

I'm have a similar question to Mark's. The words "trunk", "primary", 
"secondary" and "tertiary" implies a functional classification. A 
functionally classified road network should have each class 
(more-or-less) forming a closed network. The "motorway" class is not a 
functional classification, but a physical classification. For me, using 
the "motorway" class is acceptable because that is the way street maps 
are typically made: showing dual carriageways as the top class 
regardless of route designation or function. Anyway, only rarely in the 
case of underutilized dual carriageway roads is that an incorrect 
assumption.

Defining "trunk" as N roads is making it a network classification. Since 
trunk roads are rendered in green and we want to see the national 
network on the map, regardless of function, it works.

We have (at least) 3 different ways of classifying roads and these need 
to be blended into one classification. Our problem is also that we have 
to use the existing classes and get the OSM map to look like the street 
maps we are used to in SA. (In terms of colouring & the scales at which 
they display).

The "tertiary" class is not mentioned on the tagging standards page. Yet 
there are a lot of them, many which (like trunk) "looks" right.

My suggestion is to define the tag names as follows:

Any freeway = "motorway" (physical classification)
N roads (undivided) = "trunk" (network classification)
Major routes linking into freeways and N routes, typically low numbered 
M & R = "primary" (main roads: combination between functional and 
network classification)
Important routes linking into "primary" (main) roads (this sometimes 
will be a road without a R designation) or routes linking up populated 
places = "secondary" (network classification)
Local collector roads, ie. residential roads that carry through traffic 
(often residential roads with sidewalks) = "tertiary" (functional 
classification)
The rest = either "residential" or "unclassified".

In terms of the correct naming of the above (for legends on customized 
maps) I would go for:

Freeways
National roads
Main roads
Secondary roads
Collector roads
Residential / other

My suggestion for "tertiary" will invalidate many of the current 
"tertiary" roads - those that are not residential and are connecting 
populated places. A good example is the R104: Pretoria street connecting 
Bronkhorstspruit parallel with the N4. 
http://www.openstreetmap.org/?lat=-25.7542&lon=28.4227&zoom=13&layers=B000FTF

Comments?

Regards,

Paul.