[OSM-talk] traffic signals at dual-carriageway and complicated intersections

Lachlan Rogers lachlan at rogers.name
Tue Jul 31 01:41:41 BST 2007

I've been wondering about the best way to map complicated intersections with
traffic signals. A common example of where my dilemma arises is when there
are traffic signals at any intersection involving a dual-carriageway road.

I've been tagging each node involved in the intersecting ways, since this
seems the best method for providing route-planners with accurate
information.  However, the rendering typically involves overlapping symbols,
as can be seen here:

The other aspect of this that has bothered me is that navigation systems
would probably see duplicate sets of lights and give incorrect instructions
such as "turn left after the next two sets of lights" when it is really
referring to a single intersection.

In another thread recently, Cameron Patrick mentioned

> In my experimental maps of Australia, I've used a transparent orange
> circle on the intersection.  Look along e.g. Stirling Highway in the
> middle of this map:

> What are people doing for traffic lights on junctions of dual
> carriageways?  I've been placing a node in the middle of the
> intersection, not sitting on any of ways involved, which renders nicely
> but lacks semantic information for route planners.

I like the way his traffic signal intersections are rendered, but I think we
do need a solution that caters for route planners and navigation devices.

What is the best solution?
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