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<div class="moz-cite-prefix">On 24/05/18 13:47, Tod Fitch wrote:<br>
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<div class="">On May 23, 2018, at 7:57 PM, Paul Johnson <<a
href="mailto:baloo@ursamundi.org" class=""
moz-do-not-send="true">baloo@ursamundi.org</a>> wrote:</div>
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<div class="gmail_quote">On Wed, May 23, 2018 at 10:34
AM, Tod Fitch <span dir="ltr" class=""><<a
href="mailto:tod@fitchdesign.com" target="_blank"
class="" moz-do-not-send="true">tod@fitchdesign.com</a>></span>
wrote:<br class="">
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<div class="">On May 22, 2018, at 12:48 PM,
Paul Johnson <<a
href="mailto:baloo@ursamundi.org"
target="_blank" class=""
moz-do-not-send="true">baloo@ursamundi.org</a>>
wrote:</div>
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<div dir="auto" class="">In the case of
your typical bog standard American
residential street, I'm strongly
disinclined to agree that this is a
two lane situation. I'd be inclined
to mark unpainted lanes in the cases
where channelization regularly occurs
without the pavement markings anyway.
This isn't the case on residential
streets, as people will tend to drive
right up the middle of such streets,
only movingly right to meet oncoming
traffic and maybe when approaching a
stop sign.</div>
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<div class="">Hmmm. I guess driving culture may
vary from place to place in the US. I always
keep to the right regardless of the existence of
a lane markings. I will admit, however, that
traffic studies indicate that the average driver
will be a bit more to the center of the pavement
if there are no lane markings. Similarly, at
least in residential areas, it has been found
that drivers will generally go slower if there
is no center marking. At least that is the
rational my local government is using to remove
the center divider marking for traffic calming
purposes.</div>
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<div class="">While this may be true, most people will
shy towards center (and perhaps even stay in center)
for most of their trip down a standard width street
(which, while typically 40 feet, this is <i
class="">inclusive</i> of all features including
sidewalks, making the effective width of the roadway
closer to 25 feet, a random pull from <a
href="http://www.mesaaz.gov/home/showdocument?id=1044"
class="" moz-do-not-send="true">Mesa, Arizona's
design guide</a> blindly from Google confirms
this, with their design guide being 27 feet across
between curbs), means that two full size pickups can
(barely) pass two cars parked on opposite sides of
the street at once. That's also generously wide
compared to a lot of places, many suburban and small
town residential streets I've encountered are
open-edged with parking off the paved area, and the
paved area being maybe 20 feet on a particularly
wide street. New urbanist street designs are
similarly, deliberately, narrow as a traffic calming
measure, as parked vehicles will tend to provide de
facto ad hoc chicanes. As such, if lanes are marked
at all, it's usually at the very ends of blocks
only, where parking is prohibited, as a confirmation
that the street is indeed two-way and provide a hint
as to the default passing rule.</div>
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I have noticed that newer developments, especially infill
development, have narrower residential roads than where I live.
And I admit I did not look up current design standards. I simply
took a tape measure to a number of residential streets in my
neighborhood. The one in front of my house is 40’0" +/- 1"
between the curbs. There are sidewalks but I excluded them from
my 40’ number. Subjectively my current street seems about the
same as others in the area and the same as my in previous
neighborhood in a different city. Both neighborhoods are older,
laid out when accommodating the automobile was high on the list
of design criteria. It would be interesting to pull out the
design standards that were in effect in the 1950s, 60s and 70s
when much of our current suburbia was created. I would not be
surprised if a lot of our current stock of residential roads are
wider than the current standards specify.</div>
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<div>By the way, I don’t see a way to tag the accuracy or
confidence level for a measurement. Seems like we ought to have
something like *:confidence=*, similar to the *:lanes tagging so
we could, for example tag the width of a road as:</div>
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<div>width=18’0"</div>
<div>width:confidence=2’0"</div>
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The metrology term is 'uncertainty' .. so <br>
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width:uncertainty=2'0" <br>
To be complete there would need to be a statement of level of
confidence and coverage factor. <br>
However, for OSM simplicity, it could be assumed to have a normal
distribution covering one standard deviation .. making the
confidence level ~68% and the coverage factor ~1. <br>
Of course the stated confidence level and coverage factor would be
assessed by the next metrologist. <br>
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There is a rough wikipedea thing on it .. it is rough.
<a class="moz-txt-link-freetext" href="https://en.wikipedia.org/wiki/Measurement_uncertainty">https://en.wikipedia.org/wiki/Measurement_uncertainty</a> ... <br>
Best to look at the second reference in that wikipedia page ... NPL
do good articles. <br>
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<div>If you are only estimating from the most likely source
(allowable imagery) then you probably are not going to be much
closer than 0.5 meters or a couple of feet.</div>
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<div>A confidence/accuracy tag would probably be another can of
worms. How are you determining it? Statistically? One sigma? Two
sigma? Or assume a single measurement but with a technique known
to some typical error pattern?</div>
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<div>But I digress.</div>
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<div class="">I know that road design varies over
the world and even, to a certain extent, within
different states in the United States. So this
discussion is showing different regional points
of view. A typical, or to borrow the UK slang
“bog standard”, American suburban residential
street is wide enough for parallel parking on
each side and space for trucks/lorries to get
past one another [1]. Typical parking lanes are
about 8 feet (2.4 meters) and a typical traffic
lane is 12 feet (3.7 meters). So a total
pavement width is typically around 40 feet (12.2
meters). In some parts of the world, even in
older crowded US cities, a road of that width
might be striped for four lanes of traffic. But
a typical US residential street has no lane
markings.</div>
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<div class="">US tends to favor 9 feet per lane and 6
or 7 foot parking strips for a full size residential
street (and combine with 6 feet being the minimum, 7
becoming common, and even wider in some places for
the bike lane, this will feel quite clausterphobic
and many, if not most, drivers who will yield the
entire space to a vehicle passing a parked vehicle
first to stay out of the door zones). Per federal
guidelines, a boulevard would be at least 10,
preferably 11 foot lanes (and this will still feel
quite narrow to most American drivers).</div>
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<div class="">I can see the logic of only using
the lanes tag if there is paint on the pavement.
But that leads to another issue: It is pretty
easy from experience to glance at a photo of a
road and say it is wide enough for two lanes of
traffic. But it is much harder for me to
determine a width accurate to a couple of feet.
I don’t see a way to show a measurement error
estimate [2] and listing something as
width=40'0" implies much more accuracy than a
guess based on a quick visual survey or imagery
actually provides.</div>
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<div class="">Look for the wear marks, these will be
quite prominent in sun-prone areas and where
concrete is used. Generally speaking if there's
defined lanes that are just worn off, there will be
wear marks where passing motorists have rolled the
same spot repeatedly. This can often be confirmed
with your favorite license-compatible street-level
imagery or a survey. Though if you're using JOSM
and have suitably high resolution aerials available,
you can use JOSM to draw a line perpendicular to the
way from curbface to curbface to find the width.</div>
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My current favorite license compatible street level imagery is
from my dash cam. :)</div>
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<div>I am considering getting another dash cam and rigging up
something so that it faces out a passenger side window. I figure
that would be a reasonable way to capture a bunch of shop
details that I can’t get with a forward facing camera.</div>
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<div>Fortunately, or unfortunately depending on how you look at
it, the lane markings in my area are kept in fairly good repair
so seeing where they are worn off is often not possible.</div>
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<div class="">I am rambling. To the point, if I
were to add my photo [1] to the urban highway
tagging examples page of the wiki [3] what tags
should it have. My current guess is:</div>
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<div class="">highway=residential</div>
<div class="">parking:lane:both=parallel</div>
<div class="">sidewalk=right</div>
<div class="">surface=asphalt</div>
<div class="">width=40'</div>
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<div class="">For the specific example given by
the photo, what tags would you suggest.</div>
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<div class="">Probably closer to 34'0" wide (we're
still in agreement on customary units that the
inches should be included even when not necessary
when tagging?), since those vehicles are narrower
than a full size pickup (typ. 7 feet) and up
against the curb, and so I'm reasonably sure
there's not more than 22 feet between them, but
more than 18 feet. I'd still leave off the lanes.</div>
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Only issue with fully specifying feet and inches is that it
implies inch level accuracy with I doubt any of our road mapping
achieves. See above for a digression on tagging
accuracy/confidence levels.
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<div class="">I guess the question is: Would you leave off the
lanes=* regardless of the width as long as there is no painted
center line? If it is width dependent, at what width would you
add a lanes=* tag even if there was no center line painted.</div>
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<pre wrap="">_______________________________________________
Tagging mailing list
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