[Tagging] Permissive turn restrictions

Martin Koppenhoefer dieterdreist at gmail.com
Thu Sep 1 12:10:59 UTC 2016

sent from a phone

> Il giorno 01 set 2016, alle ore 12:00, Nick Hocking <nick.hocking at 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).

To make sure that this is an relative exceptional situation in the context (country), for your fellow mappers? in any case you could also map the traffic sign, so your precious surveyed "insider knowledge" has better chances to persist in the db.

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). 

This said, I could imagine restriction=allowed like you suggested. Logically, restriction=no would also make sense, but it bears the risk of being interpreted falsely (if someone checks for restriction=no* as short way for no_left_turn, no_right_turn etc.)


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