On Thu, Sep 1, 2016 at 7:10 AM, Martin Koppenhoefer <dieterdre...@gmail.com> wrote: > > > > Il giorno 01 set 2016, alle ore 12:00, Nick Hocking < > nick.hock...@gmail.com> ha scritto: > > > > Turn restriction seem to be either mandatory (only) or prohibitive (no) > but I think we need a permissive one, maybe (allowed) > > > Why not (also) map the ones where it isn't allowed? You probably can't > count on routing software implementing all country specific defaults (at > least currently it isn't the case with the popular osm-based ones, so they > need specific advice from the mappers in order to work well). >
Let's see, for one area in the US let's start off with creating 3+ no-u-turn relations for every intersection that has a yield sign, stop sign or traffic signal in all of Oregon and (very likely, since they're usually on par with Oregon) Idaho and Washington State, minus maybe a few hundred where signs explicitly allow u-turns. I would honestly be surprised if that doesn't put us at least well into 7 figures of new relations just right there. I've brought this up in previous threads personally regarding that region. > From a practical point of view, routing engines will generally be very > reluctant to suggest u-turns, because they tend to take a lot of time or > might even be close to impossible (with lots of traffic). > Ideally, this should be a user-selectable option (to select the user's preference/locale's default), overridden by the appropriate relation (no-u-turn or (and I'm proposing this) u-turn-ok) for smaller vehicles (bicycle, car, motorcycle...), and literally short of hell or high water avoid for more difficult to turn modes (bus, goods, hgv, horsebuggy...).
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