[Tagging] traffic lights

sergio sevillano sergiosevillano.mail at gmail.com
Sat Sep 3 15:30:21 BST 2011

El 03/09/2011, a las 12:10, Nathan Edgars II escribió:

> On 9/3/2011 6:06 AM, Nathan Edgars II wrote:
>> highway=traffic_signals means "this intersection is governed by traffic
>> signals".
>> If you want a tag for "there is a physical signal here", use a
>> different one. Using highway=traffic_signals for this will lose
>> important information about what intersections have signals (for
>> example, a router can no longer say "turn left at the second signal").
> Actually this is a bad example, since there are many reasons for having more than one traffic_signals node at an intersection. But when turning onto a trunk from a residential, for example, a router will want to put you out at a traffic signal, and this is much easier when the intersection node is clearly labeled.

are we mapping reality or "for the router" ?

the router will read path correctly anyway.

as other traffic signs 
we should map were it affects the traffic (our navigation).
give_way, stop, highway exit, maxspeed... should mark 
where you have to give way, stop, exit the highway or 
maintain a speed limit
not where the signs are.

so from this point of view you map the line in the ground 
where you have to wait, until lights let you continue.

this is easy to remember and map. 
a must for a tagging to work.

no matter where you are you can map this 
if you map the actual sign 
it will be different depending in what country you are.
us has traffic lights above and ahead the crossing 
but europe exactly where you stop. 

but the main reason is that you can describe with 
more precision and more complex crossings.

eg. it can be coincident with a pedestrian crossing
so you put both at same node. (and the router wont count two penalties)


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