[OSM-talk] Turn restriction docs

[Ulf Lamping]

David Earl schrieb:
> On Sunday 30 November 2008 03:07:02 Ulf Lamping wrote:
>> I've just added a table to that wiki page that tries to map existing
>> road signs to the corresponding restriction values.
> 
> In most situations where you see these signs they are used in 
> conjunction with a No Entry at the end of a one way street (or in the 
> case of 5 and 6 when you are joining such a street). So long as the 
> street is tagged oneway then a turn restriction as well seems overkill, 
> as all traffic is prohibited from entering.

I perfectly agree with you, that using a turn restriction when it's 
obvious from the "oneway regulations" is overkill. If people want to tag 
such a restriction fine, but I won't do.

However, e.g. here in Nürnberg we have *lot's* of smaller (residential) 
streets crossing a larger (secondary) street that have a 
"only_right_turn" sign. It would be otherwise perfectly legal to turn 
left or go straight on - no oneway involved here ;-)

Seeing the sign you want to tag on a table makes it IMHO a lot easier 
(and therefore less error prone) that you take the right turn 
restriction tag.

Maybe we add an addition, like: "There's no need to add a turn 
restriction for a road sign, if it's obvious from related data (e.g. 
otherwise you'll end up driving a oneway the wrong way)."

> It's not wrong, but it 
> doesn't add anything. Presumably the only cases we're really interested 
> in are those where traffic from one direction can't do something that 
> traffic from another direction can.
> 
> Incidentally, there is a set of pictures of UK traffic signs and their 
> meanings in the Highway Code, at 
> http://www.direct.gov.uk/en/TravelAndTransport/Highwaycode/Signsandmarkings/index.htm
> 

The "Signals to other road users" is quite funny, especially the "I am 
applying the brakes" picture.

At least the motorcyclists are not forgotten ;-)))

Regards, ULFL