[Tagging] Classifying roads from Trunk to Tertiary and Unclassified

Paul Allen pla16021 at gmail.com
Mon Aug 12 13:36:16 UTC 2019

On Mon, 12 Aug 2019 at 14:07, Martin Koppenhoefer <dieterdreist at gmail.com>

> if I don’t interpret this wrong, in Germany and Italy we are using the
> motorroad=yes qualifier for what appears to be called autovia in Spain
> (motorway like access restrictions).

Sounds about right.  Wikipedia's generic term for
motorways/freeways/autobahns etc. is
"Controlled access highway".

> We are further using highway=trunk for all roads that are similar to
> motorways (no grade level intersections, ramps) but are not legally
> motorways. trunk and motorroad are orthogonal properties/classes.

Having looked further into it, the Spanish autovias most often resemble
what we in the UK
call "dual carriageways" in construction and legal constraints.  Dual
carriageways are usually
trunk roads here.

When it comes to lesser roads, the distinction between primary and
secondary isn't solely
about width, straightness, number of junctions, etc. but also depends upon
considerations such as whether or not there are alternative routes, the
size of the places
they connect, etc.  The way in which those factors are balanced by
bureaucrats is somewhat
opaque.  There may be secondary roads connecting unimportant locations that
are as good
as, or even better than, some primary roads.

Where a country-wide classification exists, it is usual for this to be
reflected in the
numbering scheme and the signage.  In the UK it may not be readily apparent
a road is a trunk or a primary since they'll both be "A" roads with the
same style of
signage, but there's an obvious difference in signage between A roads and B
roads, and
between either of those and motorways.  It's not just the letter
designating them, but
also the colour and shape of signs that distinguishes them.

In a country where the government has classified roads in this way, it
doesn't seem like
a good idea for mappers to use their own subjective judgement to decide
which road is
a primary and a secondary.  The bureaucrats have traffic statistics that we
do not.  And
even if the bureaucrats are wrong (by some objective standard), the fact is
that all the
signage reflects what the bureaucrats say and not what one of us happens to

A tagging scheme that doesn't reflect the signage seems to me to be somewhat
sub-optimal.  Especially when we can add tags for number of lanes, speed
etc. that allow routers to make more refined decisions than relying only on
road classification.

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