[Tagging] highway=primary/secondary/tertiary - tag according to quality or usage? (Paul Johnson)

John Willis johnw at mac.com
Wed Dec 7 22:38:43 UTC 2016


On 7 Dec 2016, at 11:02 AM, Bradley White <theangrytomato at gmail.com> wrote:

>> Unless being a surface expressway (trunk) or fully controlled freeway
>> (motorway), I tend to qualify anything that averages 7+ lanes as primary,
>> 5-6 lanes as secondary or primary, 4-5 lanes as secondary, 2-3 lanes as
>> tertiary, when otherwise not otherwise being a state (secondary) or federal
>> (primary) highway.
> This is what the "lanes" tag is for. Trunk/primary/secondary/tertiary
> is not necessarily about quality or usage - it is fundamentally about
> road network importance. There are many extremely important roads in
> the U.S. that are only 2 lanes.

In Japan, it is the other end of the spectrum. The designations are purely legal designations. Many of the older, extremely narrow and winding "primary" roads have been bypassed (and officially signed as bypass roads) - but the smaller older roads still carry the "primary" designation while the larger (and in some cases, much less dangerous) bypass roads carry the tertiary designation because of legal definitions. 

A) the primary is a nationally recognized route, while the bypass was built by regional or local authorities, and the primary route is effectively replaced

B) both the primary and bypass routes are tagged as the same route and shield ref, and both follow routes that turn left and right at signals, meaning rendering color is the most important thing in Japan, in order to follow roads properly. 

I have set some of these "primary on paper only roads" to tertiary or unclassified in extreme situations where the road is almost impassible and dangerous - and totally unsigned as a way to deter people from using it, the bypass being the safer and signed route - but this is not a great way to handle it either. 

Trying to balance road classification, lanes, and legal designations is difficult when local customs and colors are not able to be managed in OSM/carto renderings.


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