[OSM-talk] UK: Trunk-Primary

Nick Whitelegg nick at hogweed.org
Mon Aug 13 09:23:35 BST 2007

On Monday 13 Aug 2007 00:13, Ben Robbins wrote:
> This question is UK based, but I think the solution could be made helpful
> to all.  I'll right this email in short then long, cuase its a simple
> point, but I'll try and cover everything.
> Proposal for "signage=<colour>", or somethign to similar effect, so that
> green signed primary roads, and green signed trunk roads can be split
> appart.
> For A roads in the UK there are 3 different main groups
> 1) Trunk Roads, roads managed by HA of A road status, rather than motorway
> 2) Primary Roads, roads which aren’t HA (according to the governments list
> on wiki), but have green signs.
> 3) Primary Roads, roads which aren’t HA, and don't have green signs.
> In OSM most people take trunk to mean a primary road with green signs (2),
> but I'm not really shore why.

Because it's the most useful and the most easily surveyed, and also 
corresponds to commercial maps. Look at a commercial road atlas or OS map and 
you'll see "green" roads in green. By tagging "green" roads as trunk, and 
other roads as primary it makes the map data more useful for navigation as 
the green roads on the map corresponds to the green signs on the ground. Some 
other arbitrary measure of "trunk" ness is less useful.

The green routes are also the recommended off motorway "inter city" roads - 
any A roads which are not recommended as long distance routes are not marked 
with green signs - admittedly more used to be. A lot of A roads seemed to be 
declassified from 'green' roads in the late 80s or early 90s.

'signage' seems an unnecessary tag. A 'green' road is not just an arbitrary 
form of signage - it is an indication that the road is suitable for long 
distance travel, and thus the 'highway=trunk' seems very sensible.


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