Felix,
yeah - the problem is not really one being smoother than the other, but the ways being different. So if I use the multiple_elements_patch only one "line" will be routable, whereas the copies are not routable. As I wan't to display the ways side-by-side the further one zooms out, the more the ways are apart from each other, or overlapping. At resolution 22 this effect is barely noticeable, on 20 it is okay, but on 18 it really gets distracting. Also roads running parallel to rivers often get inside the river because of this. For me in practice on bicycle/mtb/foot this does not matter much because I rarely use resolution 20 or lower, but I assume that for carrouting on a motorway it would be nicer to have all ways "smoothed" the same. Might be a bit difficult to change however I think, because this would need additional calculation time for non routable ways to know which nodes would be routing nodes in case a line is not routable.
OK - I understand what you're saying. I have an easy solution for that in mind and will work up a patch to try out. Cheers, Mark