[Tagging] highway=service // public road?

John Willis johnw at mac.com
Fri May 25 02:54:13 UTC 2018

> On May 25, 2018, at 2:29 AM, Florian Lohoff <f at zz.de> wrote:
> Interestingly the key:highway wiki page lists unclassified as
> the lowest classification of a road:

That’s weird - since service=alley seems to be the lowest class, being service and all - yet "alley” is a public road. 

I personally think that the idea of “alley” (urban or rural) is a great concept. 

When mapping in California, I would rarely encounter a road (urban, suburban, or rural) which would be a public maintained asphalt road with severe physical width limitations (under 2m) or is used only for local (but not necessarily residential) access. most rural roads are unmaintained tracks, and the the existing OSM tagging neatly fits. I’ve driven thousands of miles of grade 2-5 tracks all over California. 

Then I came to Japan. Japan is a spaghetti pile of 1.5m wide alleyways,  2.5-4m residential and unclassified roads, and overbuilt tertiary bypasses and trunk roads bulldozed through the whole spaghetti pile. 
Japanese maps have to accurately convey *MASSIVE* disparities in width, turn radius, shoulders, expected hazards, etc (the road classification), - which is why most consumer maps use hand-drawn “area based” maps at z16 and above, usually provided by the government or private mappers such as Mapion. It is a wholly different mapping Job than mapping anything in Southern California - except perhaps adjacent to the ocean, where service=alley is common as well.  there are simply more levels of road to map, mostly below tertiary. but we only have 2 grades until we get into tracks, which is not enough. 

Because of the extensive land management over hundreds of years, there are many public paved, maintained, yet very narrow and limited usefulness roads all over the urban centers and rural countryside, often used only by farmers to access the farming tracks that further subdivide the farming land. I personally use them when cycling - and the distinction between a public paved road that cuts through a rice field along a levee and a narrow logging track in the mountains is huge. 

This leads to rural maps of farmland that are an order of magnitude more complicated than most suburban neighborhoods in California. And since no road is straight, and everything is spaghetti pile, choosing the best route through it via basic classification is a must.

This is where unclassified falls down, and the idea of a publicly accessible, yet very restricted and narrow “allley” road comes into great usage. Using service=alley allows further classification of the road network down below unclassified - because in places with as much variance in the road network (like in Japan), this is necessary to properly convey the distinction between roads that are useful, yet remote -  and roads that loop off of them to allow tractors access to their sets of fields, or roads adjacent or on top of levees that are technically passable by public cars but are often too narrow to do so regularly. This is not necessary in all places. In addition, there are still tracks, private driveways, cycling roads, trails (ugh - no proper way to map those either), sidewalks, stairs, and other pedestrian considerations out in the middle of nowhere as well. 

In other countries, these would easily just be grade 3 unmaintained tracks. and in some places in Japan, they are. There are plenty of grade1 “paved” tracks as well. But most of these very narrow and marginally useful roads are mostly publicly maintained roads, and part of the road network - but add unnecessary noise into a mapping program. map viewers and routers should be directed to a  proper road 1m wider for normal unclassified car traffic nearby - and looking at a pile of spagetti unclassified roads is not useful to data customers, routers, nor map users. 

Dumping these tiny roads all into unclassified to be defined by “width” or by “smoothness” would not capture the true nature of the roads - they are rural alleys. not tracks. Not residential. below unclassified. 

So I map them as such, and will continue to do so, under the idea of “alley”.


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