Hi Greg,
a line is considered to be a routable line when it has a road_speed or road_classs (or both).
A few line types are special and should not be used for non-routable ways when the map
is created with --route. The style manual says
"It is known that the usage of routable types for non-routable lines in resolution 24 can cause
routing problems (e.g. address search doesn't work). The check will flag rules that assign a routable type for a line in resolution 24 without giving road_class or road_speed. A routable type is between 0x01 and 0x13 or one of: 0x1a, 0x1b, 0x16.
If road_class or road_speed is given in combination with a non-routable type, the rule is flagged. "
OK?
Gerd