[talk-au] traffic lights on dual carriageway intersections

Ian Sergeant inas66+osm at gmail.com
Sat Nov 3 20:29:52 GMT 2012


On 03/11/12 18:03, John Henderson wrote:
> 2.  It's the accurate representation of what's on the ground.  It lets
> us convey the significance of the stop lines associated with the lights.
> That's something we can't do with two-way traffic without compromising
> point 1.

Mapping is choosing a representation of what is on the ground.

By choosing to place traffic light not on the intersection node, you are 
failing to represent that "this is an intersection of two roads, 
controlled by traffic signals".  Instead you are choosing to represent 
"There is a stop line here and traffic signal and further on there is an 
intersection".

So, ideally we should have a rich enough mapping set to allow us to 
indicate both.

However,  since we can currently represent only one, I currently feel 
that it is far more important to indicate that the intersection is 
controlled, than the location of the traffic signals, or an accurate 
count of traffic signals.  This is especially true, since in the general 
case (non-dual carriageway) we can't represent these things anyway.  So, 
even if we favour the stop line location/traffic signal count method, it 
will always be wrong and unreliable.

Ian.



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