[mkgmap-dev] Road speed through urban areas

Thu Jul 16 12:53:12 BST 2020

Ticker Berkin <rwb-mkgmap at jagit.co.uk> writes:

>   mkgmap:country=XXX & mkgmap:admin_level8=* {set
> mkgmap:road-speed=-1}
> However, I haven't looked at the
> bounds/admin_level topic in any detail.

In Massachusetts, *everywhere* is within an admin_level=8.  One of these
is Boston, which is very crowded, and there are towns with 300 people
and probably more cows than that, over probably 40 km^2.   So being in
an admin_level=8 does not imply that you can't drive the posted limit.

This "admin8 is slow" rule also fails verifiability as much as
maxspeed:practical.

> Accurate road speeds must be a good idea, giving better estimates of
> journey time and, in some cases, faster routes. Even if
> maxspeed:practical isn't in the default style, I'd have it in mine if
> there was a chance of useful data for it to pick up.

To me it's clear that the right thing is to 1) tag major roads in cities
with maxspeed:practical, if you can't drive at the posted speed and 2)
respect maxspeed:practical.  Just because the wiki crowd doesn't like is
not that important; OSM has a culture of arguing about tagging in a
vacuum rather than in the context of how data consumers use it, and this
culture is broken.

> To indicate slowed speeds at lights/crossings, need --link-pois-to-way
> and, in "points", something like:
>   highway=traffic_signals | highway=crossing {set mkgmap:road-speed=1}
> This, if necessary, chops the road up and applies the specified speed
> to a short section around the point.

That sounds promising.   OsmAnd I am pretty sure adds time for
traversing lights, but it isn't trying to program someone else's routing
engine.

I suppose the traffic_signasl (and stop) could also drop the class for
longer segments if it basically works out the same.