[Talk-GB] OSM Road Classification - Trunk/Primary

[Barry McGuire]

Hi Paul,

There are two sections of primary B roads that I've been able to find,
which is against the Government's own advice for primary routes:
* B5093 Mosley Road, Fallowfield, Manchester is designated as a primary
route and is also a B road.
* B6261 at Shap, Cumbria linking A6 to M6 is designated as a primary route
and is also a B road.

The proposed change would make UK OSM consistent with the global OSM
terminology (i.e. a trunk road is a high performance or high importance
road that doesn't meet the requirements for motorway). Many of the UK's
primary routes (tagged on OSM as 'trunk') are relatively minor roads
(single carriageway, multiple roundabouts, 30mph limits) and there is no
way those should be classed as 'trunk'. There are some non-strategic
primary routes that are dual carriageways with grade separated junctions
and national speed limit (i.e. OSM 'trunk' standard), but they're in the
minority.

The proposed change has the added benefit of making the UK OSM definition
consistent with UK terminology, which has long term benefits.

It has been noted that OS maps distinguish between primary and non-primary.
Is the global aim of OSM to replicate in-country mapping standards or to
create a consistent map as possible globally? The guidance for East Africa
states "In Kenya, despite the official designation International Trunk
Roads, most of type A roads are not trunks as defined by OSM. The vast
majority of Kenyan A roads must fall into the category highway=primary." To
me this indicates OSM is aiming for a consistent standard internationally,
and currently the UK (well, mostly just England) sticks out as not applying
the 'trunk' tag to the required standards.

As Tom said this is a matter that keeps being raised so it's clearly a
persistent issue that needs resolving.

Barry

On Wed, 15 Sep 2021, 09:21 Paul Berry, <pmberry2007 at gmail.com> wrote:

> > Retaining the current system produces the quirks mentioned previously
> e.g. primary B roads and routes between primary destinations not being
> primary, which are difficult to handle - in fact each of the primary B
> roads are designated differently on OSM (one as trunk and one as secondary).
>
> If you're going to open this can of worms, at least get your
> definitions right. There's no such thing as a primary B road. Only A roads
> can be primary and non-primary.
>
> The system isn't great but there's a lot to be said for OSM in being
> consistent, even if it's not as we would have designed it if we were
> starting from scratch.
>
> Pick your battles wisely.
>
> Regards,
> *Paul*
>
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