[Talk-GB] Questions about highway classification

Richard Mann richard.mann.westoxford at googlemail.com
Tue Mar 9 11:49:40 GMT 2010

On Tue, Mar 9, 2010 at 11:29 AM, Nathan Edgars II <neroute2 at gmail.com> wrote:
> I'm currently trying to form a sort of consensus as to the best way of
> defining the classes of highway in the US, and a bit of information
> about the UK would help. I know about the definitions used
> (trunk=primary route network, primary=A roads, secondary=B roads), and
> have a few questions.
> *Is the tagging of motorway through secondary reasonably complete and
> accurate, such that OSM can be used to get a feeling of how dense the
> classes are and how they interrelate?

I wouldn't want to bet on all rural B roads being in there, but it's
probably pretty complete.

> *What's the difference between a motorway and a non-motorway built to
> motorway standards? I thought it was the ability to ban non-motorized
> vehicles, but apparently this can be done on non-motorways. Has it
> become simply a political distinction?

There are a tiny number of roads that have been built to motorway
standards, but have been classed as trunk roads because having a tiny
stretch of motorway on an otherwise trunk route was pointless. Rather
more common is where a section of a long-distance trunk route has been
rerouted onto a new section built to motorway standards. Then it gets
called A1(M) or the like. It's still a motorway. We also have some
long sections of near-motorway (dual carriageway, grade-separated
junctions) which might well be called motorway in other countries, but
aren't in the UK (eg A34). All traffic is allowed (though I wouldn't
recommend them on a bike or a tractor) and there isn't usually much of
a hard shoulder. And they might revert to lower quality without

> *Are there criteria that the Highways Agency uses to define the
> primary route network (more specific than the general purpose of
> connecting major destinations) and the difference between an A road
> and a B road? Or are changes handled on a case-by-case basis?

Don't know about formal criteria (probably not, knowing this country).
A roads link big towns and have generally been noticeably engineered
(gradients, corners etc). B roads link little towns to each other and
to big towns, and are generally wide enough for cars to pass at speed,
but not much else has been done to them.


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