[OSM-newbies] Creating a cul-de-sac

[Andy Robinson (blackadder-lists)]

Robert Funnell wrote:
>Sent: 31 July 2008 11:48 AM
>To: newbies at openstreetmap.org
>Subject: Re: [OSM-newbies] Creating a cul-de-sac
>
>On Thu, 31 Jul 2008, Oliver Lewis wrote:
>
>> If there's a large loop at the end, #2 seems correct, but without the
>> junction=roundabout. If it's a small area at the end of the road that
>allows
>> cars to turn, put a single node at the end and tag it
>> highway=turning_circle.
>> see http://wiki.openstreetmap.org/index.php/Tag:highway%3Dturning_circle
>>
>> noexit is not necessary, as routing software can figure this out.  it's
>also
>> unclear what it means / how to tag if there's a pedestrian or cycle
>through
>> route but it's a cul-de-sac for cars.
>
>Bernd is using the presence of noexit=yes in a consistency check for
>accidentally unconnected ways:
>http://lists.openstreetmap.org/pipermail/dev/2008-June/010645.html
>
>I don't know how widely accepted this usage is. It seems that the
>graphical representation of it would conflict with the graphical
>representation of a turning circle. Perhaps the two should be mutually
>exclusive, and the unconnected-ways check should include a check for
>the presence of a turning circle. Presumably the check automatically
>accounts for the presence of an explicit loop.
>

Well, I've added many thousands of cul-de-sac's in the almost 3 years of
mapping and have never added noexit=yes to any of them. Some might have a
turning circle, but the vast majority have been drawn as they are on the
ground with a "T" at the end or a short stub just before the end. Only a few
have a true turning circle and in the UK these tend to be on estates built
around a specific time. Its not common practice to build a circle (bulb or
as a roundabout) at all in the UK today.

A validator can only really be a guide to someone who knows what the data
should be like for their locality. It's fine as a sanity check in that
respect but not something that scales to everywhere. The make-up and
standard designs for streets varies enormously between country and the era
in which the road was built.


Cheers

Andy