[Tagging] noexit

André Pirard A.Pirard.Papou at gmail.com
Tue Dec 3 13:48:03 UTC 2013


Hi,

noexit <http://wiki.openstreetmap.org/wiki/Key:noexit>=yes, apparently
corresponding to this dead end signal,
<http://wiki.openstreetmap.org/wiki/Road_signs_in_Belgium#F45>  is said
to be used "at the end of a highway
<http://wiki.openstreetmap.org/wiki/Key:highway>=* to indicate that
there no possibility to travel further by any transport mode along a
formal path or route". But:

  * it's very unclear what "at the end of" means. Which? According to
    the icons (only):
      o on a way?  (50% usage) then on which end of it is the dead end?
      o on a node? seems more sensible, but how determine towards which
        way of several connected there?
  * "This tag is mainly useful where a road or path ends close to
    another way but where it isn't possible to get through due to a
    barrier or other obstruction which may otherwise look like a mistake
    for a connection to the nearby road. It helps other mappers and
    quality-check programs to understand the situation correctly." ???
  * "This tag should not be used where the way is only it is a dead-end
    for one transport mode, but where other modes can continue." ??? ???

The main question is: *is it an access restriction*? Knowing if it is an
access restriction is of course uttermost important for the Number One
OSM application to work: routing programs like on GPS: a program using
an algorithm cannot accept a vague definition.  If one thing must be
said clearly, it is that.

The article suggests it is, throwing in a reference to
Access-Restrictions
<http://wiki.openstreetmap.org/wiki/OSM_tags_for_routing/Access-Restrictions>
which in turn refers to Key:access
<http://wiki.openstreetmap.org/wiki/Key:access>, but all that without a
single word of it.
"mainly useful..." and "it helps other mappers..." suggest it is not.

Routing-wise, that tag seems perfectly useless, because the much less
ambiguous, better way to indicate no passing from one way to another is
simply not to connect them, or, in case of vehicle distinction, to
connect them with a tiny bit of segment on which the access restriction
applies the normal way.

The only one I ever noticed is here
<http://www.openstreetmap.org/?mlat=50.5329&mlon=5.5619&way=154977461#map=16/50.5329/5.5619>.
As you can see, it does not indicate which end.  It seems the odds are
in the west, but there is absolutely no access-restriction there.  When
coming from the north-west or the Rue de l'Athénée, I've seen a router
leaving the main road and taking onto that way. Go figure!

It looks from discussions that this tag is really confusing people
regarding the restriction meaning. I have read that such a vague
definition "is used for routing". Now you figure.  !!!

I doubt very much that this tags helps anybody or any quality-check
program to understand anything. A note should suffice, and I think the
best option would be to remove that confusing tag.

Cheers,

André.


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