I dont know if this is a bug or a setting that I haven't used correctly, but if I use --transparent in combination with some lines that are also present in the overview map levels, they are visible at lower zoom too: https://www.dropbox.com/s/5eg4470narcbm70/transparent.jpg The thinner lines need to be rendered only in the overview map levels. Somehow you can still see the overview map behind the normal tiles in Mapsource/Basecamp. In my lines style I have the following lines: route=hoofd [0x10601 resolution 15-18 continue] route=hoofd [0x10602 resolution 19] route=alternatief [0x10603 resolution 15-18 continue] route=alternatief [0x10604 resolution 19] options file levels = 0:24, 1:23, 2:22, 3:20, 4:18 overview-levels = 5:17, 6:15, 7:14