[Tagging] How to tag a light that is always green for certain directions?

Matthew Woehlke mwoehlke.floss at gmail.com
Mon Jul 6 20:58:57 UTC 2020

On 06/07/2020 15.28, Shawn K. Quinn wrote:
> On 7/6/20 12:59, Matthew Woehlke wrote:
>> https://www.openstreetmap.org/node/7688734125 is a traffic light that is
>> always green for straight traffic (left turns get a cycle). Is there a
>> way to tag this?
>> (I recall seeing a way to tag a signal as always green, but a) IIRC it
>> didn't distinguish always green *only* for certain directions, and
>> anyway b) I can't find it again, even using the wiki search or Google.)
> traffic_signals=continuous_green for the approach that has a continuous
> green. The left turn traffic should have a standard traffic signal node.

I can't see how that can work. The intersection has a "single" light 
(single cluster of signals, anyway; one signal per lane as is often the 
case), and is a fairly typical three-lane highway (three lanes 
westbound, that is). The lanes are not separated in any way aside from 
lane markings. Unless I am *completely* misunderstanding you (always 
possible), the only way what you're proposing would work is if the left 
turn lane was modeled as a separate way from where the turn lane starts, 
which is a) a pain to model, and b) just not done AFAICT (and very 
likely not recommended either!).


Moreover, I'm reasonably confident I've seen *actual* single signals 
that were always green for one direction (e.g. a four-lamp signal with 
red/yellow/green 'up' arrows and an always-on green right arrow).

Maybe we need something like traffic_signals:through=continuous_green? I 
suppose we could also do traffic_signals:lanes, but that seems fraught 
with parsing pitfalls, and wouldn't work anyway for e.g. a signal on a 
single lane that always has a green right arrow but a regular cycle for 
other traffic.


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