[talk-au] traffic lights on dual carriageway intersections

Alex Sims alex at softgrow.com
Sat Nov 3 10:55:22 GMT 2012

On 3/11/2012 5:33 PM, John Henderson wrote:
>> I checked some intersections in Melbourne’s CBD, and the method I saw
>> that I liked and thought the best was where there were 4 lights at
>> the intersection, but they were not placed on the intersecting modes,
>> but one node back “upstream” on each way.  I think this is good
>> because no matter which way you go through the intersection, you only
>> pass one set of lights (rather than 2 if they were placed on the
>> actual intersecting nodes).
I read it and liked it but then poked around near me but found that 
traffic signals where a divided road meets and undivided road, the 
undivided road gets a count of two. You could put the undivided (two 
ray) road traffic signals in the centre of the intersection but that 
starts to look pretty strange.

Which then leads us to possible accusations of mapping for the "routing 
renderer". Strictly speaking the traffic lights are things on poles 
placed on traffic islands as well as overhead gantries. Should we be 
tagging the physical object, ie. the signal rather than its effect which 
is most pronounced at the stop-line?

Another thought would be to tag the stopline with a direction tag to 
hint the renderer that a vehicle would stop here moving in a particular 
direction..starts to get complicated. What about wig-wags outside 
fire-stations or supplementary traffic signals applied to a level 
crossing. Starts to get tricky..

Still worth thinking about...


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