Partially mapped two-way stops

How should a two-way stop intersection be tagged if it isn’t known which approaching streets have to stop, just that not all of them have to stop?

I’ve proposed a new quest for StreetComplete that would encourage mapping traffic lights, stop signs, and yield signs at intersections. It would be limited to the U.S., where there’s no such thing as a “priority road” and stop signs are very common. It would be further limited to intersections where no traffic control has been mapped yet:

This information would be useful to both routers and renderers, especially in the U.S., where stop signs are very common but difficult to often discern in street-level imagery. (Recently I identified about 900 stop signs lacking stop bars, without really trying.)

StreetComplete is in some respects the perfect application for collecting information about traffic control, but it comes with some constraints. Unlike MapRoulette, StreetComplete needs to be able to put down something on the map in response to each task, or it’ll just ask the next user the very same question. This creates a tricky edge case at stop- or yield-controlled intersections, which need to change or create features away from the feature in question.

Normally, highway=stop is only tagged on the intersection node if it’s an all-way stop (stop=all):

But at a two-way stop, the intersection would normally remain untagged, with highway=stop stop=minor at each stop bar on the side street:

This is a problem for StreetComplete, because it currently lacks the ability to create a new node in response to a quest. Without the ability to map something in every scenario, StreetComplete would be unable to ask the user about intersection traffic control at all.

There’s actually a relatively obscure tag, highway=priority, that’s designed to go on the intersection node in a situation like this. You’d still map the highway=stop stop=minor or highway=give_way at the stop bars, but the intersection itself would end up with highway=priority to let routers know that drivers on the main road have the right of way:

Until StreetComplete is able to support node creation, would it be acceptable for the application to tag just the highway=priority node but not the nearby highway=stop or highway=give_way node manually? Would it be acceptable to tag highway=priority like this all over, in a neighborhood that happens to have a lot of this kind of intersection? Effectively, it would say that one approaching street must stop or yield while the other can go right on through, but we don’t know which one yet. It would be somewhat awkward but still useful for helping mappers locate intersections to map more thoroughly.

highway=priority currently occurs 1,679 times globally. Of those occurrences, only 117 are by themselves without a highway=stop or highway=give_way node nearby. (I’m assuming the stop/give_way node would be within 20 meters, or about 66 feet, or about six lane-widths, from the intersection node.) But some occurrences are cruft probably left over by mappers unfamiliar with this tag.

I’m posting this in the U.S. category because the proposed quest would be limited to the U.S. However, international perspectives about highway=priority would be welcome as well.

8 posts - 4 participants

Read full topic

Ce sujet de discussion accompagne la publication sur