[Tagging] [Talk-us] Freeway exit tagging

Tod Fitch tod at fitchdesign.com
Fri Aug 26 18:46:02 UTC 2016

> On Aug 26, 2016, at 10:48 AM, Paul Johnson <baloo at ursamundi.org> wrote:
> On Fri, Aug 26, 2016 at 9:44 AM, yo paseopor <yopaseopor at gmail.com <mailto:yopaseopor at gmail.com>> wrote:
> If you know which turn:lane it is you can specify it instead there's no marks. In Spain, with administrations in crisis some of them don't paint all the lanes (before the crisis they painted all the lanes). So I think we can explain the destination...if we know it, and if we want to do it (put this extra information). Truth is not the problem. Ground can change. 
> Indeed I think it's fairly safe to say, explicitly painting more than channelization lines isn't exactly a high priority for a lot of highway authorities unless it's not clear by context; I'm a firm believer that the context should be captured.

Perhaps we are dealing with a difference in semantics with one group leaning toward show what is painted and the other group leaning toward what is meant. The wiki is definitely in the “what is painted” camp but the only data consumer I am aware of treats it as “what is meant”.

While I’ve been following the wiki in my turn lane tagging, this discussion has led me to think I have been wrong: The biggest purpose for putting lane tagging in is for driving assistance while following navigation instructions. So the tagging should keep this in mind.

Consider a divided roadway with three continuous lanes in each direction, some intersections having purpose built turn lanes and others not.

In the parts of the world I drive, in the absence of marked turn lanes or specific turn restrictions, you are allowed to turn right from the right most lane and left from the left most lane. So implicitly there is an unmarked turn:lanes=left;through|through|through;right tagging leading up to each intersection that the data consumer should assume even though per the wiki the tagging, if it exists at all, will be turn:lanes=none|none|none

And if turn lanes exist, only the actual lane will be marked with an arrow on the pavement: Most through lanes are not marked even though turns from them are illegal. So the implicit marking needed by the data consumer is “left|through|through|through|right” even though the wiki says to tag it as “left|none|none|none|right”.

So the questions are:

1. How can the data consumer determine the difference between “none” meaning “left;through”, “through” or “through;right”?

2. If the determination of the meaning of “none” is by ad hoc heuristics, do those vary by jurisdiction?

While the system used where I drive seems natural and obvious, I’ve come to learn that there are significant differences around the world about what is considered natural and obvious, so I can’t assume the ad hoc rules that would decode “none” into “left;through”, “through” or “through;right” which apply where I drive would apply elsewhere. This, I think makes a strong case for tagging the intent rather than the paint on the pavement.

So based on this discussion, I will probably start using “through” instead of “none” when I am adding or correcting turn lane tagging.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.openstreetmap.org/pipermail/tagging/attachments/20160826/995e116a/attachment.html>

More information about the Tagging mailing list