Proposal talk:Shared green

Verifiability

When do pedestrians and cars have a shared green? Obviously with a phased light cycle if they turn green at exactly the same time. Or when there is signage telling drivers they need to give priority. But stop lights can be more complicated than that.

For example when the pedestrian signal turns green earlier to give them a head start? Or in the case of dynamic stop lights (adjusts to demand), how do you check that two lights can be green at the same time? And if that happens, how do you know that the lights did not calculate in the time for the car to get to the pedestrian crossing? Spaanse (talk) 10:07, 21 November 2024 (UTC)

I think these are mostly theoretical objections for edge cases. Generally if there is some shared green and some exclusive green light for pedestrians, I would still tag it as shared green, but you could add something like shared_green=limited to show that it is not always or not all the time. Practically, if you do not know when there are exceptions, you should assume it is shared. For dynamic traffic lights I agree it would be hard to verify, what do you suggest? Discourage using the tag? If you observed at least once that there was shared green then you know it can happen and could add the tag IMHO. --Dieterdreist (talk) 10:54, 21 November 2024 (UTC)

In the region where I live this is not theoretical but quite the rule that the green phases are not synchronized but have more or less overlap, that sometimes depends on the time of day. It is quite difficult to observe that exactly. I suggest that you add more precise rules. Maybe it makes a difference whether the car traffic has yellow warning lamps as well. Another thing is that you have on most of the bigger streets separated traffic lights for cars, cyclists and pedestrians that change all at different times, usually cars at last for giving more security. You should give rules whether you want to tag these traffic lights as shared_green or not. Without more precise definitions you won't be able to use the tag for evaluating the security.--Segubi (talk) 21:22, 21 November 2024 (UTC)

I would see everything except "never shared" as "shared". So all head starts or early stops should not change the value of "shared". Nielkrokodil (talk) 12:14, 23 November 2024 (UTC)

Thus this feels more like key bloat than having a benefit. Thus it might be better to use the negative form such as `not_shared_green`, This would highlight the cases when it is not the fact rather than the default of having most traffic lights situations as "shared".--Barefootstache (talk) 08:07, 24 November 2024 (UTC)

Bicycle crossings

In the Netherlands, bicycle crossings also have their own stop lights. These can also have a shared green / leading signal. Spaanse (talk) 10:07, 21 November 2024 (UTC)

You can use the tag for bicyle crossings as well. Should it be explicitly added to the proposal? --Dieterdreist (talk) 10:55, 21 November 2024 (UTC)

shared green light or shared green phase?

Is this proposal about pedestrians and cars sharing the same green light, as stated in the text, or about them only having green at the same time, as visible in the picture and the definition? There is an other proposal, too, about them sharing the same physical light: https://wiki.openstreetmap.org/wiki/Proposal:Crossing_signalization --Bauer33333 (talk) 09:43, 21 November 2024 (UTC)

It is about sharing the same green phase. --Dieterdreist (talk) 10:56, 21 November 2024 (UTC)

tagging the crossing way

Your proposal mentions only tagging it on the crossing node. What is about the crossing way? --Bauer33333 (talk) 09:43, 21 November 2024 (UTC)

I think it is sufficient to tag crossing specifics on the node, the way is only used for routing but does not get crossing information other than that it is a way that crosses a street, at least this is what I have been doing so far, I have seen people duplicating the crossing information from the node also on the way, but I never understood why this was useful, i.e. I think it is not. --Dieterdreist (talk) 10:59, 21 November 2024 (UTC)

Delayed green as additional value

Taking traffic lights more in the focus I observed here (Bielefeld, Germany), that most traffic lights delay the green for the cars and give green slightly earlier for the bicycles if there is a distinct light for bicycles. The case is a bit more complicated concerning the pedestrians but in some cases I observed even earlier green for pedestrians, followed by bicycles and then cars. I can't say whether this is a general rule. But maybe it is an idea to use shared_green=yes/no/delayed.--Segubi (talk) 12:52, 24 November 2024 (UTC)

Tag for the traffic-lights node for the cars?

I'm not sure, whether it may be (even more?) useful to tag the situation also for the cars. This could be implemented in navigational systems, so that drivers turning right could get an additional warning that they'll cross the pedestrians' and bicycles' way. It seems quite difficult to reconstruct this information from just the tags on the pedestrians node. One could use e.g. shared_green=foot, shared_green=bicycle or even just the yes/no for the perspective of the "stronger" road users. --Segubi (talk) 12:59, 24 November 2024 (UTC)

The information should be tagged at the point of conflict (the crossing node), not at the traffic signal. As pedestrians and cars both route via that node, I don't see why car navigation systems couldn't offer a warning. Discostu36 (talk) 12:59, 25 November 2024 (UTC)

Suggestion of different tags

I think the proposed key has two flaws:
1. At least in Germany, it will be "yes" in 95 % of the cases. In my opinion, a binary tag should always have "no" as the more common value.
2. A key with binary values can not easily be extended later for other kinds of phasing.
Therefore, I'd suggest using the tags phasing=exclusive and phasing=concurrent instead (Sources for these terms: [1][2]). This makes it easier to, for example, add a value like phasing=delayed (like suggested above) or phasing=priority (where pedestrians have always green until a car approaches [3]) later. Discostu36 (talk) 14:33, 25 November 2024 (UTC)

Another advantage is that the key is less Eurocentric, as the traffic signal that allows pedestrians to walk is not always green, but for example a white "WALK". Discostu36 (talk) 14:53, 25 November 2024 (UTC)