Difference to turn restrictions
I can't really see the advantage of your proposed tag over the existing turn restrictions, i.e. restriction=no_u_turn. See Relation:restriction Could you clarify that? --Mueschel (talk) 09:57, 16 November 2019 (UTC)
- No u turn restriction is used to forbid U-turning at a node (normally a junction). My proposal is used to allow / forbid U-turning outside a node, directly on a way. Imagine the highway is 5 km straight with no junction, which is mapped as a simple straight line. You want to allow / forbid U-turn on the 5-km long highway. The relation can't do that. -Miklcct (talk) 12:37, 16 November 2019 (UTC)
Can be useful for routing software at start/stop points
Currently I know no OSM tag for a bidirectional way to designate a legal restriction to cross a special road marking (a double line, an island, ..) dividing forward lanes and backward lanes. So when routing software starts a trip at the middle of the way it freely selects forward or backward direction which is prohibited for a regular (non-special) vehicle in reality. When the trip should be ended at the opposite site of the way routing software has no info to prohibit a regular (non-special) vehicle from the left (right at the left driving counties) turn at the middle of the way.
- This is true on all modes, applies to bikes and pedestrians too. If starting from a side road, turns are usually allowed across double solid white/yellow lines. ---- Kovposch (talk) 06:23, 11 August 2021 (UTC)
Is this actually useful?
Is this something that actually varies on a small scale? To take your 5-km highway as an example, are there actual stretches of highway where you can't deduce the legality of a U-turn based on the road classification ("no U-turns on motorways") and/or road geometry ("no U-turns within 100 meters of a curve")? --Carnildo (talk) 19:00, 19 November 2019 (UTC)
- It certainly is useful. A very common situation, which is rarely correctly mapped, is a bi-directional two-lane road with a solid white line in the middle. This certainly is a clear u-turn=no situation in most countries. --voschix (talk) 13:17, 9 April 2021 (UTC)
- I agree that it is useful. I was just trying to find how to add this. In my situation a sign that says no u-turns for 570 yds, most of which is dual carriageway so restrictions can be added in the usual way but the last 70 yards is a bi-directional, two-lane road with a broken white line, i.e. you can overtake on the opposite side of the road but you still cannot u-turn. It also happens to be a very wide stretch of road so it would be physically easy. TrekClimbing (talk) 20:51, 10 August 2021 (UTC)