[OSM-talk] Left-Right and opposite - Issue

[PieSchie]

Hy there,

since there are a lot of discussions about left-right tagging of ways, 
POIS and different one-way-oriented attributes I would publish the 
following for discussion.

The initial questions for my posting are:
- Tagging of footways on a street (left or right side)
- Tagging of oneway-streets with twoway-tram without making it 
dual-carriageway
- Tagging of cycleway=lane;opposite_lane where the opposite lane (lane 
for cycling in opposite direction) is on the same side as lane.

My meaning of a "street" is bidirectional and the one side of a street 
(only one direction) is a "way"

The idea would be to map/tag every street with two ways as default. That 
would mean that a normal street with two directions is realised by two 
ways between the Nodes A and B (A->B and B->A) or (A->B->C) and (C->B->A).

The Advantages would be:
- cycleway=track/opposite_track would have the meaning (cycleway on the 
right side (left in UK) in driving direction / opposite direction)
- possibility to create attributes like footway=elevated / curbstone 
that is related to exactly one side of the way
- expanded liberty to tag special ways as e.g. "oneway street with 
twoway tram" when not dual carriageway as A-B (higway=residential, 
railway=tram) and B-A (railway=tram, access=no)
 - Wen creating a bus_stop and linking it to a way (relation?), it is 
defined which direction it is going to.
- Routing would not be harmed since the direction of the way is well 
defined.

Disadvantages:
- How to render a street consisting of two ways? Something like (right 
(UK: left) half of the street in way1-attributes and the other half in 
way2-attributes. Would eventually lead to ugly looking streets when one 
way is tagged primary and the opposite direction residential. Perhaps 
rendering with the highest cathegory available between the nodes. This 
leads to
- How to combine (recognize) the two ways as one street. Perhaps 
somthing like Way1.NodeChain = Way2.ReversedNodeChain?
- Data-handling when e.g. reversing a way. Should it be possible to 
reverse a way and create two ways in the same direction, or should the 
other way be reversed as well?
- Consistency-Problems: What if both "oneways" are named differently? Is 
it possible? Which name should be rendered when rendering this way as 
one line on the map? Perhaps this Idea would need a new Object like 
"way" and "directionway" where a way consists of two directionways. 
Besides, should it be possible that one way ends an a "between-node" of 
the opposite direction.
- Database-Structure: I do not know a lot about the OSM-Database, but I 
can imagine that a change like this is hard to realize if not at all.

Have you any annotations or other concepts about this?

Greetings,
  PieSchie