[mkgmap-dev] Road speed through urban areas

Sat Jul 4 23:46:41 BST 2020

Hello,

I'm a mapper in OpenStreetMap. We have a user that uses mkgmap with
Garmin devices and he's setting road class inside cities lower than
the local convention to get Garmin to avoid being routed through slow
roads, which is bad practice. [4] I'd like to ask for some advice on
how to help him set mkgmap to avoid such problems without
disrespecting community guidelines.

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.

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.

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?

Thanks in advance for any information and advice. Best regards,

[1] https://www.mkgmap.org.uk/mkgmap
[2] https://www.mkgmap.org.uk/doc/pdf/style-manual.pdf
[3] https://wiki.openstreetmap.org/wiki/Mkgmap/help/Custom_styles#Writing_a_style
[4] https://wiki.openstreetmap.org/wiki/Tagging_for_the_renderer#General_meaning
[5] https://www8.garmin.com/traffic/index.html

-- 
Fernando Trebien