[Tagging] Question on exit-entrance rendering.

John Willis johnw at mac.com
Fri Aug 26 15:05:06 UTC 2016

Shuto Expressway system map, 24mb PDF. 


I am wondering about proper motorway entrance-exit tagging when there seems to be one tag that handles the intersection (highway=junction) and all the other information (ref, name destination) gets put on the junction node or the highway=motorway_link way (as I understand it).

The system I have been mapping/ cleaning up in Japan has directionally separate entrance-exits with either shared or separated toll plazas, shared or separated ETC toll collection, or unmatched entrance-exit pairs.

As a person who drives and sees the mistakes Google and Apple make, I see the level of complexity needed to guide a tourist around the system. 

I'm wondering, if motorways are one-way, why there is no specific method of tagging that a motorway_link is an "exit" or an "entrance" - it seems to me to be a piece of information that could make labeling and rendering a map easier. 

The Shuto expressway in Tokyo is the most complicated system I have ever seen. The level of detail provided on the system map is so much greater than a Freeway map from California because, besides the complexity of the system and the directional restrictions that motorways have because of space constraints, the separation and lack of parity of entrance-exit pairs makes figuring out where to go to enter or where an exit goes *by looking at a map* quite difficult. Even trying to reconcile what the map is showing you and the turn-by-turn information is difficult because of the insane density and complexity of such a system. 

The system map printed and online has to color the direction of traffic and whether an entrance or exit is present at each junction (pink and blue arrows) , because of the lack of bi-directional exits or entrances at each junction, along with the limited choices at interchanges. 

How how mapping ways are parsed and that information is used to create a rendered map, or that additional relational information could be determined to make a static rendered map that had enough information to be useful is a mystery to me, so maybe everything is fine and I shouldn't worry about this, but if I wanted to make a "motorway view" or provide enough information, visually, to understand this system with something like -carto renderings, it feels like there isn't enough tagging granularity to render it correctly. 

To put another way - as a mapper who is trying to tell others, via tags, what this big mess is, not being able to explicitly say "this is an 'up'entrance, this is a 'down' entrance,  and this is a 'down' exit, and together they are all called "junction C22" seems like a deficiency in tagging. 

(Towards town and away from town are referred to as 'up 上' and 'down 下' directions on all transit systems here, they don't use cardinal directions [NSEW] for most things) 

This difficulty in labeling is very apparent in Google and Apple maps- where labels are sloppily rendered because everything has to have huge official names (in Japanese and English) because of the lack of information on how everything is connected, so they just cram everything into the name field (sometimes), leading to large amounts of redundant rendered data than what is actually signed - while not rendering other important things useful to navigation. 

This spills over into service areas and other things that might be more helpful rendered as a single important point at Z10 and separate things at Z15, so being able to tag everything explicitly (maybe motorway_link=exit) or make them some member of a relation (which is abstracted away from me in iD, as it should be) is the solution I think of because the parsing and rendering of tagging data is a mystery to me (and probably most mappers). 

Is this a problem that could use a solution, or is my lack of understanding the parsing leading me to want tags that aren't really needed to correctly render such a system? Even if it can be calculated, is it easier and more friendly to new taggers to have it explicitly tagged that way?  


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