[Talk-GB] England Cycling Data project: DfT cycling data now available for merging

[Ed Loach]

Rob wrote:

> I don't see this. Right and Left tell you where the lane is, but
it does not 
> tell a user (or routing software) which direction you can ride in.
This 
> requires knowledge of which side of the road each country drives
on 
> (or forward/backward tags).

Ah, yes. I see your point. 

I was trying to say that you need left/right to say where the cycle
lanes are relative to the way to render them in the correct place,
but I can see that that doesn't tell you which way you can cycle
along them. Similarly just drawing a way on its own doesn’t tell you
which side you drive on, though there are oneway tags to cover this
(or routers can assume 2 way and not care which side).

The alternative of cycleway:forward tells routers that you can cycle
in the direction of the way (or the opposite way for
cycleway:backward), but doesn't tell renderers whether this should
be rendered to the left or the right of the way.

I guess this all relates to the issue with tagging lanes; if a road
is tagged lanes=3 how do you say how many are forward and how many
are backward? I think various proposals keep being made, but I'm not
sure anything has been settled yet?

I wish I hadn't started thinking about this now, as I think of
scenarios that I've never encountered in reality:
* twoway cycle lanes to one side of a twoway road
* cycle lanes that are oneway, but opposite direction to the
adjacent traffic lane (would this be cycleway:side=-1)

Certainly the tagging scheme for cycle lanes only really handles the
basic rendering case, I think, and requires knowledge of which side
of the way people drive for the simple routing case. And doesn't
even make clear whether it is the sort demarked with a solid or
dashed line (though perhaps there is something about this in the
wiki somewhere).

Ed