[Talk-us] Another road classification disagreement (this time with HFCS in Kansas)

[Paul Johnson]

On Sun, Sep 6, 2015 at 3:24 AM, Toby Murray <toby.murray at gmail.com> wrote:

> Sorry to start another thread on this but I just had an exchange with
> another mapper here in Kansas that could use some more opinions.
>
> I recently reclassified US 24 west of Manhattan, KS from trunk down to
> primary. NE2 had bumped it up to trunk a long time ago and I never
> felt that this was right and finally got around to changing it back.
> But tonight another user in Kansas commented on this changeset[1]
> saying that it should stay at trunk until it hits US 281 in western
> Kansas because it is classified as a "Principal Arterial" by the
> functional highway classification system (HFCS). And indeed, the HFCS
> page on the OSM wiki[2] does say that rural principal arterials should
> be tagged as trunk
>

I believe the wiki is wrong here.  HFCS certainly isn't the most important
aspect relative to OSM and is in conflict with other parts of the wiki that
properly reflect that trunks in the US are a step back from a
fully-controlled motorway.  And it wouldn't surprise me if this is causing
difficulty with some other editors as well that are taking that advise
exclusively given some other trunk issues we've had lately.  HFCS and some
state classifications tend to be less fine-nuanced than OSM's
classification, with the official classification tending to rank higher
than how it actually pieces in to the grand scheme of things: A tribe or
county authority might rank a cattle trail as primary while very few people
would say it's going to rank on the same level as undivided, uncontrolled
stretches of US 75 in the modern era.  (Go back about 80 years and you have
long stretches of Route 66 with only one lane paved or barely more than a
cattle trail even after the designation, but that was then, this is now).


> Now, I'm not necessarily opposed to taking some hints from an external
> source but my big problem with this particular case is that US 81
> (which US 24 intersects, at [3]) is also tagged as trunk. I don't
> think this classification is disputed by anyone. But US 81 and US 24
> are vastly different roads.
>

A quick examination of a ~5 mile stretch either way definitely around the
US 24/81 junction...I believe your current assessment that the two-lane
highway US 24 as primary and the four-lane, divided, partially controlled
expressway US 81 uses as trunk is a textbook example of both.


> US 24: two lanes, undivided, 65 MPH speed limit, narrow shoulders
> US 81: four lanes, divided by a 50 foot median, 70 MPH speed limit, 10
> foot shoulders
>
> I'm pretty sure US 24 also has a lot more random driveways and farm
> access roads than US 81 although 81 does have some (and hence is
> definitely not eligible for motorway tagging)
>

Indeed, US 81 is partially controlled (mix of grade separated interchanges
and at-grade junctions, driveways uncommon).

You can clearly see the difference between the roads in Mapillary. US
> 24[4] and US 81[5].
>
> In my opinion, if these two roads are tagged with the same
> classification then something is wrong with the classification system.
>

Well, hence my assessment that the wiki's wrong in this case; HFCS is only
looking at the system from a federal government perspective and in broad
strokes that miss some of the nuance.  HFCS doesn't always differentiate
between a partially controlled surface expressway like US 81 and a two lane
federal route like US 24; and I've seen instances where it ranks a state
highway that's fully controlled to interstate standards lower than OSM
would.  I don't exactly consider it any more trustworthy than TIGER.


> I'm not sure exactly what HFCS takes into consideration or who wrote
> that wiki page but this doesn't seem right to me. Can someone offer a
> defense of the wiki page or should it be changed?
>

I think a notice should definitely be added to this.  US road tagging entry
and it's talk page on the wiki also suggests that HFCS has been confusing
people, though I had thought this was mostly settled that anything fully
controlled meeting predominantly interstate standards is a motorway,
whereas partially controlled, or fully controlled but undivided (in both
case, what AASHTO geeks would call an expressway (edge case with motorway
if you want to keep alternating the tag every three blocks as in a US 81,
or WA 500 case) and in some (edge case with primary) parkways) would be
trunk.


> This user has also upgraded a lot of unpaved county roads in eastern
> Kansas to secondary because of HFCS which also strikes me as wrong.
> You can clearly see where he has done this at zoom level 9 [6].
>

I would be hard pressed to find a reason to push most county roads past
unclassified (and many in bad or seasonal repair past track).


> As I noted in the changeset discussion, this led me to encounter a
> "Warning: road may flood" sign on a dirt road tagged as secondary
> which just seems crazy to me.
>

That'd be making the same mistake as NAVTEQ did in the region, which, based
on experience when we were (very unintentionally) storm chasing from Great
Bend to Tulsa my first summer here (and had my GPS using OSM competing
against the NAVTEQ supplied data on another one, and otherwise using the
same routing engine and settings), it would have sent us down an endless
maze of flooded-to-unknown-depth dirt roads for dozens of miles (in a
classic example of "this isn't really a road so much as a bare strip of
land from where the trucks keep running over it that the county graveled at
some point").  A rally car or (more likely a tall) 4x4 with a snorkel and a
bit more enthusiasm for wanting to futz around the farm maze might have
been able to do it reliably, but not someone trying to get from A to B
safely in a 2WD utility wagon (much less under a stressful, "let's get home
between severe thunderstorms and tornadoes dropping everywhere" situation).

Sure, when it's hot and dry, station wagons and semis *could* use them, and
even reach the county speed limit on many of them, but...I wouldn't exactly
consider that a reliable expectation above less direct, but paved and
raised, highways, especially when there's already a good chance of hitting
surface imperfections or potholes high enough to high-center your average
midsize sedan without bringing weather into the mix.  For that reason,
you'd be hard pressed for me to consider anything that isn't maintained
well enough to include visible-on-the-aerial pavement markings as higher
than unclassified if it's paved or a grade1 track if it's not paved in much
of the rural midwest.  Granted, county roads are extremely variable
county-to-county based on topography and funding, but safe to assume you're
probably not going to consider it the ideal route for something sitting
relatively low with a relatively fragile suspension.
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