[Tagging] Motorway_junction = javbw confusion

johnw johnw at mac.com
Sun May 29 14:29:54 UTC 2016


Ran into a tagging issue today while cleaning up a (complicated) area of Tokyo I visited. 

https://www.openstreetmap.org/node/3851821325 <https://www.openstreetmap.org/node/3851821325> Came across this highway=motorway_junction node. Seemed in the wrong place.

Out in the Japanese countryside, the tollway exits usually have these properties:

- a “junction" has an exit in both directions of the motorway (both the “down 下 “ and “ up 上 ” directions), so adding highway=motorway_junction to the two exit nodes makes sense.
- these exits (usually) then meet at a common toll plaza between the motorway and the main road network
- which lead to a common “entrance/exit” intersection(s) on the roads linking to the tollway, which have labeled intersection signals (sometimes)
https://www.openstreetmap.org/#map=17/36.33227/139.10122 <https://www.openstreetmap.org/#map=17/36.33227/139.10122> 

- more complicated entrance and exit ramps still lead to a common toll plaza, so entering from one direction of travel or another on the normal road doesn’t limit your direction of travel on the motorway. 
https://www.openstreetmap.org/#map=16/36.3511/139.2196 <https://www.openstreetmap.org/#map=16/36.3511/139.2196> 

So how to enter the tollway seems obvious, but now there are more and more complicated entrance/exit schemes popping up, especially with "automated toll collection" exits and entrances around service areas and tunnels, like my questionable node is for.

having an entrance-exit that only serves one direction of the tollway in rural areas has led to many “wrong way” drivers on the tollway. I have personally seen two in the same spot near a one-sided junction. They assume an entrance feeds both directions (as is common), and go backwards up the exit ramp after the automated toll gates. This has led to a TON of signage and arrows and other visual cues being installed on every motorway in the last year or so - because of the rapid increase of separated entrances and exits making more and more wrong-way drivers. The offending junction pair in my area: https://www.openstreetmap.org/#map=17/36.30869/139.09130 <https://www.openstreetmap.org/#map=17/36.30869/139.09130> note, like the US, direction of travel means different exits and entrances, unlike Rural Japan (and my above examples) where a single connection to the normal road network allows access to either motorway direction, which is very common on the hundreds of junctions outside of Tokyo.

This idea of tagging just the “exits” doesn’t help when:

- the entrances are separated or have different access roads from the exits. So, so much signage is dedicated to finding entrances in complicated road networks - not tagging entrances seems to go against that.
- the “entrance”  is so far away from the exit that the label for the exit node is not useful as an implied indicator that there is an entrance there too. It’s not useful to imply an entrance in general, since there might not be one (such as the offending node’s Southbound junction is exit-only). 

This particular node marks an entrance that is very very difficult to return to, so it caused me a big headache when I missed it a few months ago. https://www.openstreetmap.org/node/773008249 <https://www.openstreetmap.org/node/773008249>. I thought I had a hundred more meters until the entrance.

- there is no exit node, just an entrance node, therefore the node label on the motorway itself can be hundreds of meters away from where the motorway_link begins, leading to missing the entrance (when used as a visual map), or, if I am understanding the wiki, shouldn’t be tagged at all. 
- The road network is so complicated, the junction labels overalap the entire rendered motorway, which visually implies there is an exit in a direction with no exit. (as in my node’s case, causing this email).

so:

- is highway=motorway_junction just for exits? it’s wiki page seems to imply/state it. Where is the corresponding motorway_entrance then when it is just an entrance? do we not need them?
- if the junction is only an entrance in one direction of travel, wouldn’t the highway=motorway_junction be more useful on the node where the link meets the normal road network (where the driver has to make a no-way-back decision), or is that not needed? 

A user in the discussion page also had a good point - the motorway_link (both exit and entrance) roads often have multiple connections, names, refs, exit_to, etc values, but the wiki page implies that getting this information onto the link way or node is not necessary for entrances. What is best? 

http://www.openstreetmap.org/#map=17/35.29627/138.94919 <http://www.openstreetmap.org/#map=17/35.29627/138.94919> the Gotemba exit ( Motorway_junction Ref=7) near Mt Fuji has “gate 1” and “gate 2” with their own entrance and exit links to handle traffic going in different tourist spots, and labeling them correctly would be nice, as it is weird. http://www.openstreetmap.org/#map=17/35.29627/138.94919 <http://www.openstreetmap.org/#map=17/35.29627/138.94919> 


Suggestion:

would something like entrance_to= or highway=motorway_entrance be a good tag? we should be able to tag, somehow, that this is a labeled and signed entrance for the tollway, and what motorway direction(s) it serves without relying on the name field (if I understand this correctly). A widening mouth/triangle head pointing onto the motorway / triangle tip ointed off the motorway might be a good rendering idea for the different entrance/exit ways (or something else visual) if words are not rendered.Something to render the entrances and exit junction labels differently, at least having junction entrances rendered only at a high zoom, while leaving the junction labels as they are now at low zoom to label the road network. 

Trying to stuff all this meaning into the name or ref for the entrance/exit motorway_link seems kinda haphazard, compared to the tagging options available to much less important details. Adding motoway_entrance (and maybe motorway exit) may help label and define these complex motorway_link road node intersections, or some other scheme to add this to the motoway_link ways themselves. 

Javbw
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