I've just discovered the overlays file but eveytime I use it routing breaks for any road where an overlay is used (mapsource either crashes or it just draws a straight line). These are very short routes (a few hundred meters) and work if I turn the overlay off. I'm confident the overlay is working because I can see the extra way in mapsource and GPSMapedit. Should routing work with an overlay or am I wasting my time? Details: Mkgmap version: 1122 overlays file contains just this: 0x123: 0x23, 0x02 the lines file contains (amongst lots of other non overlay things): highway=trunk & oneway=yes [0x123 road_class=3 road_speed=5 resolution 16] I've tried values other than 0x23 in the overlays, all produce the same result but values over about 0x2c don't display in mapsource.