[OSM-talk] Left and Right - a proposal

[Stephen Gower]

On Sat, Aug 30, 2008 at 12:26:49PM +0100, Gervase Markham wrote:
> 
> I propose that it be possible for features to be tagged using a generic
> left/right scheme, with left and right being relative to the direction
> of the way.
> 
> So you might have a road way with a node somewhere in the middle with
> (for example):
> left:highway=bus_stop
> right:parking=pay_and_display

I see from later posts that you also suggest using this scheme for cycle/bus
lanes to indicate which side of the road they should be rendered.  This
highlighted to me a general problem with the scheme. For rendering the
scheme is perfect - drawing a bus stop or a cycle lane on one side of a road
is exactly what is needed.  However, for routing you need to know which
direction a bike may travel along a cycle lane, or which direction buses
from a stop will be heading.  To derive a travelling direction from the
Left/Right terms a routing engine is usually going to need to know the local
"rule of the road" - do we just leave this to the routing engine to factor
in (needing to work out where in the world it is), or is there another
simple solution I've missed.

Sorry if this has been covered already - I'm 400 posts behind in talk/legal
combined.

s