This is a proposal to map lanes explicitly as ways. In case the lanes are divided physically don't use lane. Use a regular highway=* that is not a lane instead. Lanes are to be drawn just the same as all other highways (currently as a centre line of the lane). This proposal does not deprecate lanes=* on highways, because they can be used to check for missing explicit lanes.
To use lanes properly you should also add a Relations/Proposed/Area and attach the lane to a highway.
In the case of simple parallel lanes you are not encouraged to draw single lanes but to tag with lanes=*, unless you need to express something not adequatly expressable with parametric mapping.
Special case uneven number of lanes
The centre-lane of streets with an uneven number of lanes will keep it's normal highway=*-class and not be tagged as lane. It will also keep it's width=* indicating the total width of the highway (comprising all lanes). If you want to indicate a differing lane-width of this lane, use the lane:width=* additionally. The Key lane:width=* is synonimous to width on lanes and given on the main way indicates also the default width for lanes where not explicitly set on the lanes. Generally if all lanes share the same width, the lane:width can be calculated by dividing the width of the main-way by the number of lanes.
If the width differs and no lane:width is given, you can calculate it by subtracting the override-width of the single lanes from width and divide by the number of lanes with no given width.
For even numbers of lanes, the central way does not represent a lane itself, but represents only the centre of all lanes.
How many lanes should I draw?
- In the case of 1 lane no lanes should be drawn.
- In the case of 2 lanes there should be drawn 2 lanes (as the highway=not-lane-way is expected at the centre of the 2 lanes)
- In the case of 3 lanes there should be drawn 2 lanes (as the highway=not-lane-way is expected to be the central lane)
- In the case of 4 lanes there should be drawn 4 lanes (as the highway=not-lane-way is expected at the centre of the 4 lanes)
- In the case of 5 lanes there should be drawn 4 lanes (as the highway=not-lane-way is expected to be the central lane of the 5 lanes)
All optional tags are used to override for the specific lane the tags/values given to the main highway=*. You can basically use all keys you usually set on highways, plus the additional turn-key. If the Keys aer the same then the main way, don't set these tags to simplify editing and reduce redundancy.
- turn=no/left/right/u to define the kind of lane dependant on the way it goes or if present the arrow marking on it. If the arrows indicate "straight on" or are not present, you should tag turn=no. This is also the default value if turn=* is not present.
- ref=* if the ref of the street-way is different from the one of the lane.
- width=* for the width of just the lane (distance between the centre of the adjacent road markings or estimated). If no width is tagged at the lane the width can be asumed with highway-way-not-lane:width divided by the number of lanes.
- lane:width=* on lanes is equal to width=* (shall not be used, use width instead) but can be used to express differing lane-width of the main way as well as indicating a default width for all lanes if set on the main way (which cannot be a lane but must be a regular highway=*)
- surface=* for different surfaces of the lane. If not set it is asumed to be the surface of the main way.
Rendering and Editing
Lanes could be rendered to improve rendering in high-zoom-scales (closeups). In Editors they will be visible, but should be distinct from other highway=*