[Talk-GB] Secondary, tertiary and unclassified

[Mark Goodge]

On 04/11/2015 18:05, Lester Caine wrote:

> The point I was trying to make was that Secondary, tertiary and
> unclassified are essentially the same level of importance for road
> navigation and so treating them differently in rendering ( or routing
> rules ) adds an incorrect importance to one over the other.

They're not at all the same level of importance. Making that assertion 
betrays a fundamental ignorance of the UK's road network.

> In the
> absence of any other evidence I'm planning to simply re-tag the problem
> unclassified routes as tertiary for now, but I can make a case for all
> being secondary so they get rendered with the same separation from the
> sections of the road system that should not be used for through routing.

If a road can be used for through routing then it probably is tertiary 
rather than unclassified[1]. That's a reasonable rule of thumb for 
making the decision, in the absence of more reliable information. But 
secondary is very well defined, and is part of published open data. 
There's never going to be a reason to tag a road as secondary that isn't 
already known to be.

[1] This is one of the reasons I don't like the new style, with white 
for all smaller roads. The difference between tertiary and 
residential/unclassfied is quite significant in UK road topology, and 
needs a clearer distinction than just the width of a digital brush 
stroke. But that's a different issue.

Mark