[Talk-us] Freeway exit tagging

Rihards richlv at nakts.net
Thu Aug 25 21:28:24 UTC 2016

On 2016.08.26. 00:15, Jack Burke wrote:
> Freeway exit tagging
> I am totally confused.
> What is the proper method to use turn:lanes to tag freeway lanes
> approaching an exit, where the exit branches directly from an edge lane
> without being part of the freeway itself, but the freeway lanes are not
> signed with an arrow, such as this one?
>  http://mapillary.com/map/im/7igAGXSa6EsUYlTIujXchw
> Through examples[1], the wiki shows that when the freeway lanes *are*
> signed, then "through;slight_right" appears to be the correct value.
> The wiki examples also appear to indicate that "through" is *only*
> appropriate when there is corresponding signage.  The wiki is also very

referencing the previous topic in talk-us about how lane tagging should 
follow lane _markings_, i'd like to suggest to only map the legally 
allowed driving directions, no matter how we arrive at them.

mapping the road markings seems extremely strange - what if they are 
very faded, when do we map them ? is there a threshold of % of the paint 
left ?
what is there are no road markings but there are signs ?
do we remove those tags during the winter in some regions ?

mapping of markings separately also seems to have no functional benefit. 
the information should be useful for navigation software - or, more 
importantly, for the end user (no matter which software delivers useful 
service to them). they don't really care how exactly the allowed 
directions are marked, as long as they get through it all without 
crashes and fines.

> clear what to do when an edge lane is an exit-only lane
> ("slight_right"), and what to do when a lane is signed for both through
> and right turn ("through;right").  So what's the right thing to use when
> there is no "through" indicator, yet there is an upcoming branching
> exit?  By inference from what's contained in the wiki,
> "none;slight_right" appears to be the appropriate value, but it looks
> like a lot of people are disagreeing with that[2], even though it
> appears to be the only logical conclusion.  Others think that
> "through;slight_right" should be used because it's the reality on the
> ground[2] despite the lack of paint/signs.
> I'm bringing this up because I'm trying to get exits on I 75 in Georgia
> and Florida tagged with destination and lane guidance (though only one
> navigation app processes lane guidance AFAIK, but I hope that by adding
> the data, others will take it up, too), and don't want to waste my time
> tagging it incorrectly.  One helpful group trying to fix what they
> consider incorrect lane counts & tags, turned a bunch of my
> continue-or-exit lanes tagged with "none;slight_right" into exit-only
> lanes[3] with just "slight_right".  I'm worried about switching to
> "through;slight_right" because I don't want some *other* do-gooder
> coming along later and similarly breaking lane guidance because there's
> no arrow on the ground or on a sign.  Thus, I am now at a standstill
> because there doesn't appear to be any correct tagging scheme for this
> incredibly common situation.
> Note:  I am intentionally leaving the proposal for "transit:lanes" out
> of this, both because it hasn't been voted on, as well as it doesn't
> appear to cover this situation any better than turn:lanes does.
> --jack
> References:
> [1] http://wiki.openstreetmap.org/wiki/Key:turn
> [2] https://lists.openstreetmap.org/pipermail/tagging/2016-June/029335.html
> [3]
> https://lists.openstreetmap.org/pipermail/talk-us/2016-August/016643.html
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