Unposted overtaking restrictions
Seems that the wording I wrote years ago omitted a crucial point: overtaking bans are not always visible in the form of solid lines or traffic signs. In most countries overtaking is also forbidden when the visible stretch of road isn't long enough, because of a hill summit or because of curve, or other similar (road layout) reason limiting visibility. On smaller roads these aren't marked in any way, but they can not be deduced from any data we have, nor could they be from any dataset we could reasonably expect to become available in the next decade or so (terrain models etc.). (If a vehicle has broken down in such a "blind spot", getting around it with extra caution is AFAIK not consider "overtaking", but who-knows-what-it's-called in English mandatory special manouver.)
Tagging overtaking=both in a tight bend where nobody can legally overtake a moving vehicle would seem utterly stupid. Even if the height of the driver's seat has a minor effect in some of the hill summit cases, the exact length of the implied restriction is less interesting than the fact that it exists - and hgv drivers sitting really high can use overtaking:hgv. As to the effect of the slower vehicle's speed (you need less room to overtake farm machinery than a car going 10 under the limit), the length and curve of the section can help somewhat?) To make it clear in these cases that there are no official indicators of the restriction, one could tag (for example a hill summit) as below. On one side, where the osm way(s) first go "uphill":
- overtaking=backward up to the highest point (meaning: The drivers going downhill see far ahead, but those going uphill don't see enough for a legal overtake)
- overtaking:forward:reason=visibility (or just omit the ":forward" in the middle) (The reason why you can't overtake, even if there are no signs, is that you don't see far enough.)
and then after the hill summit, where the osm way(s) go downhill:
Naturally, the "highest point" above can be an intermediate in an uphill slope, the point where the incline changes so much that the visibility is reduced even if both sections are uphill in the same direction.
The only other option would be to omit overtaking=* completely for both those stretches, and to use for example overtaking:forward:visibility=no + overtaking:backward=yes. Which makes it more error prone for consumers, as there's a risk of conflicting data and a higher risk of mappers mixing up their intentions and the data. When the actual restriction is in overtaking=*, it's always either/or. Alv (talk) 07:08, 3 October 2013 (UTC)
- While it's possible on that on major roads the solid middle line in that direction is continuous through the sideroad intersections, effectively banning left turns, quite a few intersections introduce a gap in the banning line just to allow left turns. Also, I don't remember seeing any of these overtaking bans extending through intersections in urban areas. Additionally, if we were to assume the left turns were banned, we would still lack a way to indicate which intersections did allow the left turns when within the overtaking restriction. Alv (talk) 05:52, 4 September 2015 (UTC)
- Does exists a Tag that banns left turns for major roads? Those that you have to drive to the next roundabout to turn left. Pedrobv (talk) 17:19, 4 September 2015 (UTC)
Definition over "overtaking"
A definition of "overtaking" would be helpful. In the US we use the term "passing" whether you are using a lane going in the same direction as you to pass someone or a lane going in the opposite direction. If I apply overtaking=no to a four-lane road, I want to know what that implies or if it is wrong/assumed. Germyb (talk) 21:01, 27 August 2017 (UTC)
- My interpretation is that the key is about overtaking/passing, regardless which lane is being used for that. So on a four-lane road, it would still ban overtaking, even if you don't need to use the opposite direction's lanes for that. --Tordanik 18:02, 29 August 2017 (UTC)