[Talk-us] Freeway exit tagging

Jack Burke burkejf3 at gmail.com
Mon Aug 29 18:59:03 UTC 2016

So it sounds like the general consensus is that I should probably be using
"through;right" at places like shown in my original pic, instead of
"none;right", based on the usage rather than the signage (presuming, of
course, my tagging doesn't conflict with a sign, which shouldn't happen
since everyone should be driving like the signs say in the first place).

On Fri, Aug 26, 2016 at 4:17 PM, Jesse B. Crawford <jesse at jbcrawford.us>

> Where I live (San Francisco, CA, USA), lane arrows are generally added
> for one of two reasons:
> 1) It isn't obvious what the authorized use of a lane is, when there is
> e.g. a right, slight right, and through option with various lanes for
> each - especially when there are multiple slight_rights as sometimes
> happens.
> 2) To provide advanced warning that a lane you're in will have limited
> options in the future (such as "HWY ONLY" written in lanes). The
> location of these warnings varies, they're sometimes just yards before
> the intersection and sometimes a block or two back - presumably
> depending on how easy a traffic engineer thinks it will be to change lanes.
> Lane arrows are only present in some cases though - and in my
> cross-country driving experience, I have found California to be
> unusually thorough about lane arrows, so they're probably present more
> of the time here than they are in much of the rest of the country. For
> example, lane arrows to indicate a merge_to_left are virtually never
> used in the state of Oregon (this may even be ODOT policy?), but are
> almost always present in California.
> This is just a difference between two neighboring states in a country
> with a reasonably precise traffic control manual. Lane arrow practices
> are presumably even more different between countries (e.g. in the parts
> of Mexico I visit, I don't think I've ever seen one).
> My point is this: the practice of marking lanes with arrows varies by
> jurisdiction and by how recently the intersection has been painted. In
> many cases, in the US at least, it depends on whether the intersection
> is straightforward to navigate for humans or not. It probably also
> depends on whether or not violations have been observed there - here, at
> least, they sometimes respond to too many accidents at an intersection
> by putting in physically larger stop signs. I suspect the same is done
> with land arrows.
> Do any of these factors in road markings change the actual ground truth
> of the intersection and its navigation?
> I think this is the point that Rihards was getting at, somewhat
> hyperbolically. Road markings like lane use arrows and signs are usually
> themselves representations of the intersection to come, much like a map.
> When we produce a map, we shouldn't be making a map of someone else's
> map of the intersection. We should be reflecting the way the
> intersection actually is. Which, yes, is sometimes designated only by
> restricting signs, but often it is not, and is instead restricted by
> standard rules about the usage of lanes (i.e. no right turns from a lane
> other than the right curb lane, UNLESS markings indicate otherwise).
> These rules, too, vary by jurisdiction, so if the map is going to be
> general for global use it should express them.
> --
> Jesse B. Crawford
> https://jbcrawford.us
> jesse at jbcrawford.us
> GPG 0x4085BDC1
> On 08/25/2016 11:30 PM, Paul Johnson wrote:
> >
> >
> > On Thu, Aug 25, 2016 at 4:28 PM, Rihards <richlv at nakts.net
> > <mailto:richlv at nakts.net>> wrote:
> >
> >     On 2016.08.26. 00 <tel:2016.08.26.%2000>: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
> >         <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.
> >
> >
> > This is a pretty nice summary of what I was getting at in the previous
> > thread on talk-us.  Especially given how common it is to not have the
> > turn arrows in the first place.  I'm a firm believer that the wiki is
> > wrong on this one and the ground truth for turn lane tagging should be
> > the actual application of the lanes, with or without the presence of
> > supporting signage or pavement markings.
> >
> >
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