Contradictory Instructions For Tagging Motorway Junctions (aka Exits)

General talk
1

The instructions for tagging freeway exits in the OpenStreetMap wiki seem to be contradictory.

According to http://wiki.openstreetmap.org/wiki/Key:destination, if a freeway exit sign says “Main Street; Exit 15”, then the exit’s node’s tags should be:

  • Destination: Main Street
  • Ref: 15

OSRM, OsmAnd, and garmin.openstreetmap.nl follow this approach.

However, if I follow the instructions for the USA at http://wiki.openstreetmap.org/wiki/Exit_Info then I tag as:

Exit Node:

  • Ref: 15

Exit way:

  • Destination:street: Main Street (assuming the way directly intersects with Main Street)

I have verified that OSRM and garmin.openstreetmap.nl have trouble providing instructions when I tag a freeway exit using the latter approach. Garmin will say “Exit to 15” and OSRM will just say “Continue onto unnamed road”.

Is there any sort of consensus right now in the OpenStreetMap community on this topic?

I am concerned that while the latter approach looks great from a tagging perspective, it breaks all the software that uses the data. If I should really be using the latter approach, then I will file feature requests for OSRM, the Garmin export, checkautopista2, and probably OsmAnd (once they update their OBFs).

2

http://wiki.openstreetmap.org/wiki/Key:destination fairly clearly ways it applies to ways not nodes. In fact the icons showing on which sort of objects it can be used show nodes as forbidden! I’d say that both references agree.

I think you need to take this up with either Garmin, or the people who wrote the preprocessing software for Garmin maps, as the fault seems to lie in one of these places.

Using your first method because it has the result you prefer would be a case of tagging for the renderer <http://wiki.openstreetmap.org/wiki/Tagging_for_the_renderer>, and is something you must not do.

3

Er, no.

One the specifics of Garmin maps, the most widely-used mechanism for creating Garmin maps from OSM data is “mkgmap” and that uses an entirely user-configurable mechanism to map OSM features to Garmin ones. Many different pre-built maps are made for different purposes, and they will map different features in OSM to a Garmin map depending on that (a road satnav map would not show walking trails, for example).

On the more general point, the way of describing motorway exits, it sounds from the text above that you’re in the US - you might find the discussion at http://www.openstreetmap.org/user/mvexel/diary/36263 and the graph on http://wiki.openstreetmap.org/wiki/Key:exit_to helpful. I think that the US community discusses stuff more at https://lists.openstreetmap.org/pipermail/talk-us/ than on this forum.

The wiki is often “inconsistent” - a page can get written by one person, describing their favourite way of tagging something, and sometimes their view of what is “correct” doesn’t match everyone else.

4

Thank you for catching my mistake.

I will take SomeoneElse’s advice and ask about the current working consensus using the mailing list.