The UK uses the trunk tag differently from the rest of the world. In most of the world it implies bicycle=no and pedestrian=no but in the UK it implies bicycle=yes and pedestrian=yes. You will see old acknowledgement of the issue going back to 2008 on the talk page for the tag, but people have just lived with it. The UK tagging of single carriageway, open access roads as trunk routes is not incorrect in the sense that in the UK these roads are known as trunk routes even though they may be relatively minor roads.

As a cyclist this causes me grief as although there are UK specific producers of Garmin maps, they have issues and I would like to use alternatives of which there are several produced by European producers. Sensible routing is impossible and in the past, I have been told that the map producers will not change their automated routines to do something different in the UK.

There are two obvious solutions to update the source: to implement a new tag across the UK which acts as a trunk tag but is simply a different tag (e.g. trunk_uk), or alternatively perform a countrywide attribute replacement where the UK default attributes of bicycle=yes and pedestrian=yes are explicitly set. The first one would confuse existing producers but an easy tweak to adopt, and the second would be transparent but require a one off update and there is the possibility that new routes would not be maintained correctly (but how often are new major trunk roads created).

Not knowing how I would get agreement on either of these matters, how would I go about this? Secondly, if a one off update was agreed to be the correct approach, how could I get someone competent to do this?

asked 24 Jul '14, 08:58

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Spenny
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Hi Spenny, did you ask this at the UK forum as well, http://forum.openstreetmap.org/viewforum.php?id=5 or the tagging list tagging-request@openstreetmap.org. But try the first, before your going to use the last adress.

(24 Jul '14, 09:27) Hendrikklaas

Another solution possibly, although I've not tried it, would be to build your own Garmin map which did what you want. see https://www.google.co.uk/webhp?sourceid=chrome-instant&ion=1&espv=2&ie=UTF-8#q=mkgmap

(24 Jul '14, 10:22) andy mackey
3

Andy, these days I am trying to be a leech not a techie!! I think it is a more general problem I am trying to solve for everyone as there are lots of baffled users out there who don't understand the underlying mapping issues, and it is straightforward to resolve for either visitors from abroad who will use their favourite map source or for UK users looking for something else.

(24 Jul '14, 11:05) Spenny
2

@Hendrikklaas - please don't send people to the UK forum. A quick scan of the posts there will show that the only people in it are people stumbling on it by accident. Most GB-specific discussion takes place on the talk-gb mailing list; there's also an IRC channel #osm-gb. For those parts of the UK geographically part of the island of Ireland there's talk-ie and #osm-ie too.

(24 Jul '14, 12:59) SomeoneElse ♦

Hi Someone else, I won’t. But I’m a little disappointed about the community then, since the forum sites are meant for it aren’t they for local questions ? Your part of it or is that my mistake ? I expected the forums to be meant, to concentrate the questions at one place, too bad no success it’s scattered all over.

(24 Jul '14, 13:42) Hendrikklaas
1

@Hendrikklaas Different OSM groups use different communication mechanisms - some use OSM lists, some non-OSM lists, some the OSM forum, some Facebook (and I'm sure there are more). There's nothing wrong with the forum as such, but for UK-specific questions it's not a good choice if you want to get an answer.

(24 Jul '14, 14:11) SomeoneElse ♦
showing 5 of 6 show 1 more comments

Taking the last questions first:

Not knowing how I would get agreement on either of these matters, how would I go about this?

There'd have to be a discussion and a general acceptance among GB mappers that "We're Doing It Wrong" and need to change. The best place to start that discussion would be the talk-gb mailing list - it's the most widely used forum among mappers on this island. OSM follows geography rather than politics for the GB and IE mailing lists, so if you were proposing to change Northern Irish usage you'd want to include talk-ie too.

Secondly, if a one off update was agreed to be the correct approach, how could I get someone competent to do this?

Assuming the "discussion and general acceptance" happened, I'd ask for a volunteer at that stage. What they then did would have to follow the mechanical edit policy (essentially discuss it, document it, then do it).

However, taking a step back from the "how", what you seem to be saying is "some data consumer not in the UK doesn't seem to understand how data in the UK is tagged, therefore we must change all the data in the UK". This strikes me as something that might be described as a "hard sell" to the mailing list :) . I'd expect that routers would need to regularly adapt to different data in different countries; in the USA and Australia and elsewhere a "road" might be something that in the UK and most of western Europe would never be described as that.

What I suspect that you'd need to do would be to explain the problem a bit more clearly. Can you give an example of a journey where "Sensible routing is impossible" and explain why the route that is suggested is not sensible? With regard to the "there are UK specific producers of Garmin maps, they have issues" part, can you explain what these issues are - using specific examples if possible?

Current UK trunk tagging is nicely verifiable on the ground, so I'd expect quite a lot of resistance to a change - you'll need to provide good arguments why a change makes sense.

In addition, as @andy mackey says it is fairly straightforward to create your own Garmin maps. If you can explain what problems you're getting it might be possible to get a solution for you without any data changes. FWIW I've always found that I get better routing answers on a Garmin by removing data that I know that I want to not route along before sending it to the device (private roads in the case of foot routing; all non-road tracks and paths for car routing).

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answered 24 Jul '14, 13:24

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SomeoneElse ♦
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accept rate: 15%

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Thanks, that points me in the right direction.

Without extending the discussion too much here, in simple terms the issue is that cycle routing on the Garmin is badly impacted with European sourced UK maps as they will not cross an A road marked as trunk - it will come up with bizarre 20 mile diversions. I can produce a 1 mile route in Derbyshire that shows the problem.

It's not a question of one group being right or wrong, but it is an unfortunate situation that there is internationally an incompatibility between the conventions.

(24 Jul '14, 13:51) Spenny
3

As Richard has already mentioned, different country-specific defaults isn't limited to trunk roads. There's a page here that describes lots of differences:

http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access-Restrictions

(27 Jul '14, 23:13) SomeoneElse ♦

This is a problem with the Garmin map producers, not with the UK map.

Access defaults always need to be interpreted on a national level: see the wiki for a fairly comprehensive list. Bicycle and footway access on trunk roads is just one of many possible regional variations. Eliminating them all is unrealistic in the short term, and would need to be agreed across the OSM community in the long term.

It's also worth noting that the UK is not the only country where bikes are permitted on trunk roads. They are also generally permitted in the US, Hungary, Spain (though Spain isn't in the above table), and so on. A mass edit would be a sticking plaster to fix the issue in the UK while leaving the (much bigger) US unresolved.

Producing country-specific bike routing isn't difficult. cycle.travel, for example, permits bikes on trunk roads in the UK but not in (say) Germany. One easy solution along these lines would be for the Garmin map producers to use Osmosis to change tags when preprocessing the UK extract - for example, changing highway=trunk to the highway=trunk_uk you suggest.

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answered 24 Jul '14, 13:48

Richard's gravatar image

Richard ♦
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accept rate: 19%

edited 24 Jul '14, 14:08

1

Richard's example of post-processing is easy to implement in mkgmap.

(24 Jul '14, 19:16) SK53 ♦
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question asked: 24 Jul '14, 08:58

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