[Talk-GB] Primary or Trunk?

[Tom Hughes]

On 02/11/13 18:47, Jonathan wrote:

> I'm not clear with the distinction of a Trunk road in the UK. The wiki
> suggests a trunk road is "high performance roads that don't meet the
> requirement for highway
> <http://wiki.openstreetmap.org/wiki/Key:highway>=motorway
> <http://wiki.openstreetmap.org/wiki/Tag:highway%3Dmotorway>" which to me
> would suggest an A road that is a dual carriageway.  Further on in the
> wiki it says that any A road in the UK  signed with "Green" signs is a
> "Trunk" road.
>
> I know of many "Green" "A" roads that aren't much more than country
> lanes, they are definitely not "high performance" and I don't feel they
> should be "Trunk" roads, I feel they should be "Primary" roads.

It's really very simple, and has been discussed here many, many times 
before and I'm sure there are multiple pages on the wiki covering it.

First, forget the question of which roads are formally designated as 
trunk roads by the Department for Transport (which is not very many 
these days).

Second, understand that there is something called the Primary Route 
Network defined by DfT which covers those A roads connecting specific 
major towns. Those are the A roads with the green signs, and are what we 
tag as highway=trunk. Other A roads are highway=primary.

In many cases those will be major roads, often ex trunk roads, but in 
more rural areas like the highlands they might look more like a B road 
does in other parts of the country. That is irrelevant though.

In the UK it is really only residential/unclassified/tertiary where you 
need to make a judgement call. Everything else has a well defined mapping:

   Motorways => highway=motorway
   Green Signed A Roads => highway=trunk
   White Signed A Roads => highway=primary
   B Roads => highway=secondary

Hopefully that will explain everything ;-)

Tom

-- 
Tom Hughes (tom at compton.nu)
http://compton.nu/