[mkgmap-dev] Road speed through urban areas

Sun Jul 5 02:55:14 BST 2020

Fernando Trebien <fernando.trebien at gmail.com> writes:

> I've downloaded the source code [1] and read through the default
> styles in ./trunk/resources/styles/default/ . If I understood
> correctly, it sets road_speed=3 (60km/h [2]) for highway=secondary and
> road_speed=2 (40km/h [2]) for highway=tertiary. Those are reasonable
> in rural areas, but too fast in urban areas, where average speeds
> usually drop by around half of their real speed limit.I also found
> rules for handling the speed limit in maxspeed=*, but it seems like
> his issue would persist even when this tag is provided in map data.

The basic problem is that if you are using default speeds baseed on osm
road type, that's a clue that speed limits rae missing.

The next problem is that there is maxspeed and maxspeed:practical, and
if you cannot drive at the speed limit usually, you should

  set maxspeed:practical

  check that if maxspeed:practical exists, mkgmpa uses it as the speed
  limit

> I think it might make sense to write a custom style [3] setting
> road_speed=2 for highway=secondary and road_speed=1 (20km/h [2]) for
> highway=tertiary. Perhaps this would then break some rural routes.

That may make a map that works in one area, but it just moves the
problem.

> I've found that Garmin supports traffic data, [5] but I'm unsure if
> this works with maps converted using mkgmap, as I don't own any Garmin
> device. Do you know?

I have never seen a claim that it works.