Proposal:MotorwayExit

Status

Proposal

Proposed-by

Cdaller

Proposed-date

2007-06-18

Rationale

I just was told that "highway=motorway_junction" already exists as a map feature, so I guess this page is not needed anymore! --Cdaller 20:42, 12 July 2007 (BST)

Use existing keys to indicate a motorway exit. The difference to Motorway_Exit is that the tag should be applied to a node, not a way!

Applies to

Nodes

Usage

The tags should be applied to the node where the motorway_link separates from the motorway (resp. the primary_link from the primary).

Tags

File:At-s6-exit-17.jpg

A motorway exit in Austria

A motorway exit (or any other exit) could be tagged as:

<tag k="highway" v="exit"/>
<tag k="name" v="Gloggnitz"/>
<tag k="ref" v="17"/>

Rendering

In low zoom maps, all exits of an area (both directions) should only be shown as one single larger dot (with a name and the exit number). If there is more than one exit in a small area (both directions) the multiple larger dots cover each other, so there seems to be only one exit dot. Not perfect, but works visually.

At higher zooms, each single exit (both directions) can be shown with name and number.

Example rendering was added to tilesAtHome styles and the highway exits at Rottenmann/Austria were rendered to show. The rendering is not perfect in color (yellow dots on motorways), style, size or text positioning!

Misc

I do not think we need new keys to indicate a motorway exit. As we have name and ref, why not use them? In Austria, I just saw that even parkings on motorways are given a number, so I just used "ref" there as well. I do not think that special "exit" keys (like "exit_name" or "exit_nr" should be used).

Comments

And what about motorway entrances?

I suspect the rendering will need to be more sophisticated than described to get usable results. (it'll need to find the centrepoint of the junction by averaging the points for it) 09:02, 19 June 2007 (BST)

I would just tag the motorway_links as ref=18. A renderer may still decide to render the exit as a dot on certain scales, but an exit is, physically, not a dot but a lane, and should be represended as such. -- Relet 11:17, 19 June 2007 (BST)

I don't know how it works in your part of the world, but here, a junction between two motorways often has two references - as an example Junction 42 on the M1 is also 29 on the M62. This would ideally suit tagging the node where the motorway_link leaves or enters - if you tried to tag the link itself, it would need breaking up into two ways, one with one ref, and the other with the other. Morwen 12:13, 19 June 2007 (BST)

I see the exit as a node feature as well. It is the point one leaves the motorway. It's like a door, which I would not see as a linear feature. --Cdaller 21:55, 10 July 2007 (BST)

I support this proposal. An exit is a node where you leave the motorway, similar to a checkpoint. Tagging the linear junction IMO causes troubles. --SlowRider 07:37, 11 July 2007 (BST)

What troubles does it cause? --Hawke 15:13, 11 July 2007 (BST)

I think Junction Number would fill this goal just fine. I don't think the highway key is a good fit for this particular tag. In Morwen's use case, the exit ramp/motorway_link from the M1 to the M62 would be number 42, while the exit ramp/motorway_link from the M62 to the M1 would be number 29. That is, only the exit ramp is numbered; the entrance is not. I particularly like the idea of standardising on "The tags should be applied to the node where the motorway_link separates from the motorway". --Hawke

Why use a new key if we can handle all this with "old" keys (name, ref)? --Cdaller 21:55, 10 July 2007 (BST)

Because highways are linear; a highway "node" makes no sense. --Hawke 15:13, 11 July 2007 (BST)

There are quite a lot of node highway tags on our features page (stop, toll_booth, gate, bus_stop, etc.). And not all features on highways are linear! And an exit is exactly one point (for me :-) --Cdaller 16:16, 11 July 2007 (BST)

I think there is a difference between the map data as used for navigation and used as a plain map. Used as a map, the junction number is a node placed in the centre of the junction. If you wanted to use the junction, you'd not actually pass this node. For navigational purposes, the junction is really composed of the (up to) 4 slip roads that lead on and off the motorway. For that reason I'd think a different tag is useful. --asc99c 11:18, 27 July 2007 (BST)

I just was told that "highway=motorway_junction" already exists as a map feature, so I guess this page is not needed anymore! --Cdaller 20:42, 12 July 2007 (BST)