I am coming to the conclusion that the garmin routing engine has some definite limits as to what it can do in terms of route quality. Tweaking the road class/speed parameters can make a difference but the real solution to achieving a really good route is to take pity on the gps and put in a few strategic way points. Given some hints, I think it does OK. I feel that it's just too much to expect of the gps to be able to route long distances optimally without a bit of help from the human. I'm not saying that the current implementation of routing support cannot be improved, I am sure that it can. But even if our code was perfect, the routing is still going to be influenced by the quality of garmin's routing engine and, crucially, the quality of the OSM data. Cheers, Mark