Hi Brett, Maybe you cna have a look at the Lambertus generic new style maps. Recently I have put a dashed overlay line next to the highways to indicate the surface is unpaved. highway ~ '.*(trunk|primary|secondary|tertiary|unclassified|residential|minor|road).*' & mkgmap:unpaved=1 { add mkgmap:road-speed = '-1' } [0x10002 resolution 21 continue with_actions] highway ~ '.*(byway|living_street|service|cycleway).*' & mkgmap:unpaved=1 [0x10002 resolution 23 continue with_actions] The styles you can find here: http://code.google.com/p/mkgmap-style-sheets/source/browse/#svn%2Ftrunk%2Fst...
Strange as it might appear in Europe but gravel roads that can be impassible by normal cars are classed as National Highways in Australia. Still have not worked out the best way to render gravel roads but still keep their road level rating. Duplicating all the road lines for gravel will likely mean running out of Garmin hex codes for line type. Also OSM surface rules are rather weird. Bit like the hiking classifications that are very word long, but at least they are a standard. Tempted by the technic used by some for bridges to render gravel roads.