Talk:Three-point turn

message: :The following 'graph was originally the second 'graph of a 2-'graph contrib, whose 1st 'graph is now in the "Turn/Turning in title"  section.
How I came here is I want to say that metaphorically in computer programming a standard swap is a three point turn "let temp = b, let  b = a, let a = temp." That is a fairly standard term, a three point turn there, and I wanted to add that to "Three point turn" but it is a redirect. Of course I can quote sources etc. going back to the sixties, e.g. Brooks, and more modern. Si Trew (talk) 10:11, 4 May 2010 (UTC)
replies: text: Great input, thanks; i'm on it & at your talk page, i will solicit more content.--Jerzy•t 14:15, 2 September 2010 (UTC)
replies: text:  Standard swap embodies such an article, and i've added a  HatNote Dab to the article accompanying this talk page.--Jerzy•t 18:49, 5 September 2010 (UTC)
thread_title:  (Programming term) 

message: IIRC, the article addressed cars specifically, and i've generalized it with
: ... unarticulated vehicles with reversible propulsion systems...
bcz everything in the procedure would apply to a bicycle with direct drive (or for that matter, gears but no freewheel)! More practically, it applies to farm tractors
bcz virtually everything abt the procedures themselves applies that generally -- even with axles of radically different length as shown in the tricycle-like :File:RogerTractorLarge.jpg below (tho i hesitate to guess whether the space advantage of the reverse-3-pt extends to those cases).
--Jerzy•t 14:15, 2 September 2010 (UTC)
thread_title:  More general vehicles 

message: What the official drill describes is, i think, an easy special case. More or less as i put in my fact tag, this sounds like not an "approved method" for doing K-turns in any situation where a U-turn fails, but a pedagogical tool for preparing drivers for the test on a standard test road that allows far more margin. I can see reasons why that is not an irresponsible approach for driver ed: If you can handle a moderate one, you'll start picking up the rhythm and unconscious logic of the method; when the potentially necessity turning beyond the desired final direction, and then returning to center only when it's obvious you're out of the woods will come naturally and mostly unconsciously.   But if i am right, it means we have failed at our task of making our description of the real-world process accurate.   The theoretical situation is this: given a road-width, which vehicles can do a K-turn on it depends on three parameters of the car: width, length, and turning circle. Expressing those parameters as fractions of the road width gives you a 3-D graph of "car design space", with surfaces dividing (perhaps only hypothetical) cars that can make the U-turn from those that require at least a K-turn, and those from the cars requiring higher-order turns, and those from vehicles that have to drive thru without reversing direction. But you can get a better feeling for the range of difficulty, and the consequences of more or less difficult, by some simplifying assumptions: insignificant length and insignificant width. I drew circular arcs around a physical cylinder and parallel lines with a ruler. The ratio between road widths the barely permit a U-turn and barely prevent a K-turn, for my simplification, is about 2.9! If you're relatively close to the U-turn succeeding, your backing takes you toward the opposite curb rather than the original one, and you don't even need to approach the curb in the backing move: you're on your side of the road when your backing brings you parallel, so you just shift into forward and straighten the wheel. As you consider progressively narrower roads, you reach a stage where how far beyond center you have turn the wheel before straightening out and driving away depends on how close to the original wall you backed up. At the edge of needing a 5-pt turn, you back at the full limit of steering, from the opposite curb to the original one, and only if you turn the wheel all the way (past center) back to its opposite limit do avoid hitting the opposite curb a second time, barely skimming past it before steering over to the center of your lane. I'd like to believe that whoever runs driver ed in the UK had bar graphs plotted, showing, for each of a representative sampling of brands and models, how wide the road has to be for the driver to be able to skip the last n sub-steps of the full K-turn process, and concluded that the missing steps interfered too much with getting the remaining steps straight to be worth including them in the official instructions.   IMO we should acknowledge their version by pointing out where it leaves off, in a complete any-width K-turn procedure.--Jerzy•t 14:15, 2 September 2010 (UTC)
thread_title:  K-turn from hell 

message: This article is about a thing. We have the name of the thing at great detail, what the Canadians name it, and discussion about it here, including a picture of a tractor... but what in Sam Hill IS it? I know about a 2-point turn: drive along, slow down, turn say left, stop up against the curb (1st point), reverse the transmission and the steering, which backs the vehicle across the road and ends up facing opposite the original direction. A 2nd stop (2nd point) and shift transmission into forward and you drive off, having made the equivalent of a U-turn on a road that would be too narrow for it. A THREE POINT turn would add a 3rd stop and reversal, which would leave the vehicle driving off in the original direction. Is that what this thing is? Should not this article offer some definition? Friendly Person (talk) 03:02, 25 February 2012 (UTC)
replies: text: You may have a point about the name, but yes, it's as you describe. Three elements of travel, but only two points where you stop and change direction. I've added a brief description, source to the Canadian online source. It would be neat to find, or create, a copyright-OK diagram to include. PamD 09:02, 25 February 2012 (UTC)
thread_title:  What is it