Using a OSM map, my Nuvi 510 handles roundabouts as ordinary streets with exits, i.e. the voice does not say “enter the roundabout and take the 2nd exit” - as it is happening in the original garmin map - but says “turn right” when entering the roundabout and then “proceed 50mt and turn right” etc . The same goes in the graphics: the icon on top-left does not display a roundabout.
I double-checked with potlatch and the roundabouts I went through are defined correctly (i.e. as roundabouts).

Is this the expected behavior or is my map broken somehow? (I did not generate myself but downloaded the ones available from


It is not the expected behaviour. mkgmap-generated maps that use Garmin type 0x0c for roundabouts should result in the Garmin unit recognising roundabouts as distinct and different from other junctions. I don’t know how the GFOSS guys generate their maps, however.

Try using a map from just to double-check that there isn’t a problem with your Nuvi.

ok -thanks, I’m giving a try!

Thanks, it works with Lambertus maps!

By the way, one of the roundabout I tested does not work as expected: coming from west or south and going north, the way going east is ignored i.e. coming south and going notrh the voice says “enter the roundabout and take the 1st exit right”, while it should be the 2nd exit right (the path to follow on screen is correct). I checked with potlatch but the roundabout seems defined ok. Any clue?
I read in the past of a possible issue with roundabout incoming/outgoing streets if they are too close, but I am not able to find the doc again.


I just tested that roundabout using and routing from south of the roundabout to via Tiziano Vecellio works as I would expect (i.e. you take the first exit at the roundabout and head east).,45.3628792&end=11.933586,45.3615241&pref=Fastest&lang=en&noMotorways=false&noTollways=false
So there’s nothing wrong with the roundabout. It just seems that mkgmap isn’t counting the number of exits properly. If this really bugs you, it would be worth sending an email to the mkgmap-dev mailing list to see if someone can track down the reason.

thanks for double-checking! In the meantime I found some docs that might help out: (documented in

I’ll try with mkgmap-dev - thanks!