Hi Toby,
As I said, bad source data is more of an issue - I'm cleaning up quite a bit as I go.
Good!
One thing that caught me by surprise was approaching a roundabout and just being told to keep left - it wasn't until I reached the splitter island that I got given the roundabout exit to take. I guess this is the opposite of the missing-exits problem, in that the island was large enough to count as a separate road for the eTrex's purposes.
Did it think that the splitter was, itself, a left turn?
One thing I do have a concern about is mixing speed rules into the lines file - I've patched my style as instructed, but now all roundabouts are drawn the same, because there's a rule for roundabouts for speed purposes.
Not sure I understand that. The default rules now look like this: junction=roundabout & highway=trunk [0x0c road_class=3 road_speed=5 resolution 16] junction=roundabout & highway=primary [0x0c road_class=3 road_speed=4 resolution 19] junction=roundabout & highway=secondary [0x0c road_class=2 road_speed=3 resolution 20] junction=roundabout & highway=tertiary [0x0c road_class=1 road_speed=3 resolution 20] junction=roundabout & highway=unclassified [0x0c road_class=1 road_speed=2 resolution 21] junction=roundabout [0x0c road_class=0 road_speed=1 resolution 21]
(I'm too lazy to introduce roundabout rules for each highway class). I think that this probably needs a re-think, because it would be nice to combine information to give a better resultant speed guess (including features such as traffic signals, number of lanes, etc - and for roads in "place=*" as described[1] on the OSM wiki).
[1] <URL: http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Maxspeed >
The maxspeed tag should be effective as support for that was recently added by Bernhard. Cheers, Mark