<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
</head>
<body>
<p><font face="Verdana">Sorry if I jump into this discussion with
some delay, I don't want to ignore what previously has been
discussed but as being from a region (Africa), where most (up to
90%) of roads are unpaved I do think are local experience can
provide some valuable input.</font></p>
<p><font face="Verdana">In this regard I would ask several
questions: <br>
</font></p>
<p><font face="Verdana">1. Does a simple term as "gravel" or
"fine-gravel" or any of the other values accurately reflects the
top surface (as in the surface=* tag) of a road or track ?</font></p>
<p><font face="Verdana">2. Does this surface tag adds any valuable
information for the road user, to determine if it's traversable
or usable in all seasons ?</font></p>
<p><font face="Verdana">3. Does adding a smoothness key improve the
issue raised in question 2 ?</font></p>
<p><font face="Verdana">Answering these questions is very complex,
no short answer covers the whole scope of issues related to
unpaved roads, to my opinion both on a global as a local African
scale, but I will do my best.</font></p>
<p><font face="Verdana">1. Does a simple term as "gravel" or
"fine-gravel" or any of the other values accurately reflects the
top surface (as in the surface=* tag) of a road or track ?</font></p>
<p><font face="Verdana">Most of the gravel roads are NOT pure gravel
or crushed rock (no matter if it's fine, coarse or other
grades). Civil road engineers always make a mixture of gravel
with another material, taking into consideration the
availability of the different materials, the stability of the
applied top surface when used in dry, wet and other (like icing
in winter) conditions and it's hazardous or less favourable
impacts on the surroundings and the users.<br>
So have to evaluate how much gravel is mixed with ground, sand
or clay-like material (like the murram we use locally). Gravel
can be from river deposits, having mostly smooth round shapes
and poor interlocking. SO for the road user not interesting as
not providing a stable traversable surface. Crushed rock or
rubble has mostly better interlocking purposes, so can provide a
better stable and traversable surface. Both gravel shape types
are mixed with fine materials like ground, and or clay to
decrease run-off of the fine aterial during rain. Negative is
the noise and in combination with clay like materials, increased
dust, which can have severe impacts on the environment and other
road users. <br>
A lower amount of gravel mixed with clay-like materials,
deceases the amount of dust and noise but makes the road more
slippery, up to the level that you can't even traverse it by
foot.<br>
Roads or tracks without high frequency traffic grow grass on the
fine material in-between the gravel. So the top surface becomes
grass, no longer gravel. It decreases run-off, washboarding and
other effects and improves even the interlocking of the gravel
and thus the stability.<br>
</font></p>
<p><font face="Verdana">This problematic and careful balance is true
for most gravel roads across the world. So saying a road
surface is gravel or fine-gravel is essentially wrong, because
it's a mixture. Up to what percentage of rock or stone content
or coarse sand should be called gravel ?<br>
It varies across different engineering standards and even local
standards across the world. So does it make sense to add more
specific information as just paved or unpaved ? In my opinion
not, so I stopped, and many others did in Africa. A road or
track without a long term consistent surface is just tagged as
unpaved and we would even deprecate the use of any other values.
Because in many cases it's not consistent in the long term
(grass growth, erosion, dust).</font></p>
<p><font face="Verdana">2. Does this surface tag adds any valuable
information for the road user, to determine if it's traversable
or usable in all seasons ?</font></p>
<p><font face="Verdana">No as already explained above. Even if we
take seasonal variances into account the surface and usability
of the road changes a lot during wet, dry or icy conditions. One
might argue and say adding a seasonal tag may improve this. Yes
it can, but not in conjunction with the surface tag. Like a low
gravel content murram road is perfectly usable for all vehicles
and on foot in the dry season, however becomes so slippery and a
mud pool during the wet season that it's not usable at all. A
higher gravel content might make it usable and stable enough to
use during the wet season, however again this depends on the
gravel amount, it's shape and how it's mixed (just the top or
also the sub layers). So saying surface=gravel doesn't add any
value in regard to this question.</font></p>
<p><font face="Verdana">3. Does adding a smoothness key improve the
issue raised in question 2 ?</font></p>
<p><font face="Verdana">No. An unpaved road might be perfectly
smooth during the dry season. During the wet season, all the
water runs off over the unpaved road, it turns into a small
river with detrimental erosion effects. SO after a heavy rain
shower and drying up it turns into a surface full of grooves and
craters, when dried up hard as burned clay, no longer smooth at
all. In some cases not even traversable any more by a normal
high 4x4 vehicle. Often repairs take place manually after a few
months. <br>
</font></p>
<p><font face="Verdana">So to me, discussion about surface values
other then unpaved or paved doesn't make a lot of sense as just
to describe visual appearance, not forgetting that most gravel
roads are mixtures.<br>
To add information to a map as to describe if unpaved roads are
traversable in different seasons needs a different tagging
scheme. As was and is done on many old maps. We have
all-season roads, we have seasonal roads where you should
describe the major hazards, being, dust, noise, smoothness and
sliding in dry, wet and winter conditions. A complete new
tagging scheme. It might need further detailing as to wide and
narrow tire vehicles and on foot.<br>
All efforts which we use today for smoothness and surface is
just short term, non-conditional information, lots of
information that can't be used to provide conclusive routing or
road conditions.</font></p>
<p><font face="Verdana">The same might be said for paved roads. We
have dense closed and open asphalt, concrete with surface
impregnation or smooth, ribbed concrete ... all with the purpose
to improve road conditions during wet , dry and or icy
conditions. Reduce the hazards described. Adding a surface tag
as asphalt or concrete doesn't provide the required detail to be
conclusive. So deprecate the values, just leave it as paved.
Invent a new tagging scheme, which might be similar as the one
for unpaved roads.<br>
</font></p>
<p><font face="Verdana">Greetings,</font></p>
<p><font face="Verdana"><br>
</font></p>
<p><font face="Verdana">Bert Araali<br>
</font></p>
<p><font face="Verdana"><br>
</font></p>
<div class="moz-cite-prefix">On 15/04/2021 10:56, Mateusz Konieczny
via Tagging wrote:<br>
</div>
<blockquote type="cite" cite="mid:MYJX6As--3-2@tutanota.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div>For long time this tag was described at Key:surface page as <br>
</div>
<div>"Broken/crushed rock with sharp edges, known as ballast on
railways. Usually loosely arranged.<br>
</div>
<div>Typical size for road and surface construction range between
4 and 8 cm".<br>
</div>
<div><br>
</div>
<div>( <a href="https://wiki.openstreetmap.org/wiki/Key:surface"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/Key:surface</a>
)<br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>But it turns out that surface=gravel is primarily used for
roads where far smaller <br>
</div>
<div>pieces of rocks are used.<br>
</div>
<div><br>
</div>
<div>---------------------------------------------------------------------------------<br>
</div>
<div><br>
</div>
<div>It is result of <br>
</div>
<div>- "gravel roads" term is often used in many countries for
something where far smaller pieces<br>
</div>
<div> of rock are used, some of such roads would qualify for
surface=compacted.<br>
</div>
<div> See <a
href="https://wiki.openstreetmap.org/wiki/File:Gravelsign2.jpg"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/File:Gravelsign2.jpg</a><br>
</div>
<div>- "gravel" and equivalent terms in other languages is often
used by people to refer to pieces<br>
</div>
<div> of rock far smaller than 4cm<br>
</div>
<div>- there was not good tag for roads with surface of small
loose gravel <br>
</div>
<div> (surface=fine_gravel at <a
href="https://wiki.openstreetmap.org/wiki/Key:surface"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/Key:surface</a>
has<br>
</div>
<div> "A multilayer pavement with a stone or gravel basis and a
topmost surface of firm, granular grit,<br>
</div>
<div> basalt or quartz," what anyway excluded cases of some
gravel thrown on earth/mud/drt )<br>
</div>
<div>- surfaces matching old Wiki definitions are existing but
really rare <br>
</div>
<div> <a
href="https://wiki.openstreetmap.org/wiki/File:%C5%A0t%C4%9Brkov%C3%A1_cesta_u_Pl%C3%A1%C5%A1t%C3%ADku.jpg"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/File:%C5%A0t%C4%9Brkov%C3%A1_cesta_u_Pl%C3%A1%C5%A1t%C3%ADku.jpg</a><br>
</div>
<div><br>
</div>
<div>---------------------------------------------------------------------------------<br>
</div>
<div><br>
</div>
<div>How one may know that Wiki definition mismatches actual use?<br>
</div>
<div><br>
</div>
<div>assumption:<br>
</div>
<div>Surfacing roads/paths/etc with track ballast-sized pieces of
gravel is extremely rare<br>
</div>
<div>(though it happens)<br>
</div>
<div><br>
</div>
<div>but in actual use surface=gravel is extremely common, far
more common that<br>
</div>
<div>old Wiki definition.<br>
</div>
<div><br>
</div>
<div>So actual use clearly mismatches wiki definition.<br>
</div>
<div>In addition, many people using surface=gravel were unaware of
this definition and unaware<br>
</div>
<div>that such surfaces described in Wiki actually exist!<br>
</div>
<div><br>
</div>
<div>See <a
href="https://lists.openstreetmap.org/pipermail/talk-au/2021-March/014445.html"
moz-do-not-send="true">https://lists.openstreetmap.org/pipermail/talk-au/2021-March/014445.html</a><br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>---------------------------------------------------------------------------------<br>
</div>
<div><br>
</div>
<div>So:<br>
</div>
<div><br>
</div>
<div>It turns out that surface=gravel is for anything from
"basically compacted" to<br>
</div>
<div>"basically track ballast".<br>
</div>
<div><br>
</div>
<div>I recommend checking <a
href="https://wiki.openstreetmap.org/wiki/Key:surface"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/Key:surface</a>
in your language<br>
</div>
<div>and updating definition to match actual tag use.<br>
</div>
<div><br>
</div>
<div>It would be nice to find some good tagging for surfaces like<br>
</div>
<div><a
href="https://wiki.openstreetmap.org/wiki/File:%C5%A0t%C4%9Brkov%C3%A1_cesta_u_Pl%C3%A1%C5%A1t%C3%ADku.jpg"
rel="noopener noreferrer" target="_blank"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/File:%C5%A0t%C4%9Brkov%C3%A1_cesta_u_Pl%C3%A1%C5%A1t%C3%ADku.jpg</a><br>
</div>
<div><br>
</div>
<div>surface=track_ballast? surface=huge_gravel? surface=ballast?<br>
</div>
<div><br>
</div>
<div>It would be also nice to find some more specific values for <br>
</div>
<div>cases of small gravel thrown on mud/dirt/grass - as
surface=gravel<br>
</div>
<div>turns out to be very unspecific ability to tag this in detail
would be great<br>
</div>
<div>(useful especially for cyclists)<br>
</div>
<div><br>
</div>
<div>surface=small_gravel? Something else?<br>
</div>
<div><br>
</div>
<div>---------------------------------------------------------------------------------<br>
</div>
<div><br>
</div>
<div>PS AAAARAGAGAHHA. Tag used over 1.5 million times had actual
use and OSM Wiki<br>
</div>
<div>definition completely and utterly mismatched.<br>
</div>
<div><br>
</div>
<div>And we need new tags and resurvey of 1 500 000 elements to
have useful information about surface.<br>
</div>
<div><br>
</div>
<div>Right now surface=gravel may be both <br>
</div>
<div><a
href="https://wiki.openstreetmap.org/wiki/File:%C5%A0t%C4%9Brkov%C3%A1_cesta_u_Pl%C3%A1%C5%A1t%C3%ADku.jpg"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/File:%C5%A0t%C4%9Brkov%C3%A1_cesta_u_Pl%C3%A1%C5%A1t%C3%ADku.jpg</a><br>
</div>
<div>and<br>
</div>
<div><a
href="https://wiki.openstreetmap.org/wiki/File:Gravelsign2.jpg"
moz-do-not-send="true">https://wiki.openstreetmap.org/wiki/File:Gravelsign2.jpg</a><br>
</div>
<div>that for many purposes are worth distinguishing.<br>
</div>
<div><br>
</div>
<div><br>
</div>
<div>Arghhh.<br>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
Tagging mailing list
<a class="moz-txt-link-abbreviated" href="mailto:Tagging@openstreetmap.org">Tagging@openstreetmap.org</a>
<a class="moz-txt-link-freetext" href="https://lists.openstreetmap.org/listinfo/tagging">https://lists.openstreetmap.org/listinfo/tagging</a>
</pre>
</blockquote>
</body>
</html>