Thoughts about detailed tagging of road and lane markings on highway lines

For cycleway (and other) markings, see Proposal:Separation#Symbolic_separation:_marking
Outsourced thoughts from the road marking revision proposal:

Using on `highway=*` lines to specify `lane_markings=yes`

Instead of mapping road markings as separate features, the values of this scheme can also be used on the highway line itself, esp. to specify the already existing unspecific lane_markings=yes property. Although “lane markings” is an unfavorable term, as it is unclear which elements of the lane it refers to (centerlines, lane dividers, road edge markings, ...), it is already established and should therefore serve as a basis for additional tagging options.

TODO Short textual explanation how to use the tagging.

TODO Explaining defaults: solid road edge, dashed lane dividers, country specific colours and overtaking/change indicators.

TODO Replacing in use divider=* tagging.

The following examples illustrate the use of road marking values on highway lines:

Two lanes with lane divider
	A dashed lane divider and solid road edges. `lanes=2` `lane_markings=yes` `lane_markings:lane_divider:stroke=dashed` `lane_markings:road_edge:stroke=solid` `lane_markings=yes` alone may be sufficient according to country specific defaults.
	A yellow dashed-solid double lane divider and solid road edges. `lanes=2` `lane_markings=yes` `lane_markings:lane_divider:stroke:left=dashed` `lane_markings:lane_divider:stroke:right=solid` `lane_markings:lane_divider:colour=yellow` `lane_markings:road_edge:stroke=solid` `lane_markings=yes` + `overtaking=backward` (driving on the right) may be sufficient according to country specific defaults.)
	A dashed lane divider, but no road edges. `lanes=2` `lane_markings=yes` `lane_markings:lane_divider:stroke=dashed` `lane_markings:road_edge=no`
	A (dual carriageway) oneway road with dashed lane divider and solid road edges. `lanes=2` `lane_markings=yes` `lane_markings:lane_divider:stroke=dashed` `lane_markings:road_edge=solid` `lane_markings=yes` alone may be sufficient according to country specific defaults.
	A (dual carriageway) oneway street with 2 lanes, right lane (bus lane) separated by solid lane divider. `lanes=2` `lane_markings=yes` `lane_markings:lane_divider:stroke=solid` `lane_markings:road_edge=solid` `lane_markings=yes` + `change=no` may be sufficient.
No lane dividers
	No lane dividers, but solid road edges. `lane_markings=no` `lane_markings:road_edge:stroke=solid`
*More than two lanes / more than one lane divider (using `:lanes=` scheme)*
	A (dual carriageway) oneway road with 4 lanes, left lane separated by solid lane divider, others by dashed lane dividers. Note: The lane divider `lanes=*` notation is oriented towards the marking for the next lane on the left-hand side. There is no lane divider to the left for the first (leftmost) lane, so the value for this lane remains empty and the entire value starts with `\|`. `lanes=4` `lane_markings=yes` `lane_markings:lane_divider:stroke:lanes=\|solid\|dashed\|dashed` `lane_markings:road_edge=solid` `lane_markings:road_edge:left:colour=yellow` `lane_markings=yes` + `change:lanes=no\|not_left\|yes\|yes` may be sufficient according to country specific defaults.