[OSM-talk] Obvious turn restrictions

Ed Avis eda at waniasset.com
Fri Jul 8 18:04:39 BST 2011

Nathan Edgars II <neroute2 <at> gmail.com> writes:

>North Elk Vale has been split into three ways with four relations on 
>each side of the overpass. And for what? To prevent a router from 
>telling you to turn right in the wrong part of the intersection?

I think the essential problem is that you need to split a way into several bits
to add these restrictions.  It would be better if the schema for restrictions
didn't require you to break ways in two.  For example it might take a 'from' and
'to' way, an intersection node and an optional direction such as 'northbound'
to disambiguate.  That is slightly unclean in a strict geodata sense but
perhaps better than the death by a thousand cuts we currently suffer when
modelling complex junctions with the need to split a way at each point there is
a junction node with some kind of restriction.

That's just one idea.  Another would be a 'lightweight' turn restriction schema,
supplementing but not replacing the existing one, where properties can be tagged
on the node itself ('no_turn', 'no_right_turn_northbound') avoiding the need
for relations at all.

Or perhaps editors just need better support for editing ways as a group to cope
with the reality that things tend to get chopped into smaller and smaller bits
as the map improves.

Ed Avis <eda at waniasset.com>

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