The mkgmap default style doesn't understand maxspeed:practical.

Thanks.  I was unclear on this.

I would suggest that mkgmap should in the default style use the first

one of these that is defined:

  maxspeed:practical

  maxspeed:advisory (yellow sign, in the US, not a requirement, but advice)

  maxspeed (legal limit)

I am unclear on if advisory is used in non-US places.  Here we often

e.g.  have yellow "45" signs on curves on roads with "55" limit (white)

signs, and on exit ramps (slip roads in en_GB, *_link in osm).

Sometimes the advisory speeds are sensible, some times they are way too

low and occasionally they are too high.  A great case for using

practical to fix them.

I would expect this to be quite necessary in rural UK and IE, as it

seems there is a tradition of 100 km/h or 60 mph outside town centers,

but at times roads often narrower/twisty such that at least I didn't

think it wise.

(The US doesn't do this so much; very rarely is the legal limit unsafe.

There are dirt roads where :practical should be used, though.)