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

Bradley White theangrytomato at gmail.com
Wed Dec 7 02:02:55 UTC 2016


> 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. High lane counts, high speed limits,
or expressway-like features can be indicative of a a higher
classification, but it is not conclusive. There is a long article on
the wiki about road classification being fundamentally about network
importance and not road characteristics. One way I like to think about
it when deciding is to imagine if the segment of road in question
popped out of existence - how much of an impact would it have? Does it
simply mean a mile or two detour, or will it now take hours longer to
get from major city center to another major city center? How many
people would be cut-off from the rest of the world if the road
disappeared?

I agree for the most part with your point about road classifications
in the U.S. being stacked too high; especially, it seems the "primary"
tag is over-saturated. At least on the west coast of the U.S.,
however, I think there is an under-utilization of trunk classification
as well as unclassified. The former, because we still don't have an
agreed/uniform definition of "trunk" for the U.S.; the latter,
probably because it is not rendered distinctly anywhere but one zoom
level.

Tagging by road quality or characteristic leads to the weirdness that
is present at lower zoom levels, where trunk roads pop in and out of
existence in the middle of nowhere. This is worthless for
cross-country navigation, which is what motorways and trunks are
about. I could talk about this ad nauseum, but I'm getting off topic
now.



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