[Talk-us] Update on potential highway classification reform

[Kevin Kenny]

I think it makes sense for the OSM highway class to have rules at the level
of individual states in the US, just as it has rules at the level of
nations in the EU. Except for the Interstates, the US really has no
national highway classification system. US highways are actually nowadays
numbered by agreement among the states they serve, and the FHWA functional
classification is intended to prioritize Federal aid for highway funding.
Virtually all road designation, construction and maintenance is carried out
by the states.

New York's GIS appears to have classifications that make a modicum of
sense. There's an Arterial Classification Code that attempts to document
that-which-is (rather than allocate funding), for the express purpose of
routing preference and decluttering at low zoom levels. Its top couple of
levels of classification appear to be a decent match to 'motorway' and
'trunk'.

Note that this is distinct from the Federal functional class, and the NY
GIS system tabulates both.  Federal functional class is "what the road
ought to be, and we'll use that to allocate funds for improvements', whie
arterial class is "how the road actually is used - in terms of
appropriateness for routing and zoom level"

At the most significant levels, the chief points that are likely to be
controversial:

There are a few data entry gaffes. Most of these are obvious, such as the
fishing access service way https://www.openstreetmap.org/way/20084827 being
classed as 'minor arterial', probably because it was inadvertently selected
along with NY 23A.

There are short motorway segments like NY 85 from I-90 to the first
roundabout that are merely class 3.  (Then again, that segment is
'motorway' only by the 'three consecutive interchanges without a level
crossing' rule. It has four.

Some suburban freeways, and nearly all the parkways, are class 2 rather
than class 1. This list has seen arguments in the past about roads like
these, with some people contending quite passionately that 'motorway' is
inappropriate for a road with `hgv=no`, or for a suburban freeway that does
not carry significant interurban traffic. The chief cause for the
disagreements appears to be that for the larger cities, including the
suburban freeway network clutters the map unreadably at low zoom levels.
Do we need an auxiliary tag to identify 'suburban freeway?' (Most
three-digit Interstates, some NY parkways, NY 27 in Suffolk County, NY 33
and 198 in Erie County, and so on)?  It might help allay a lot of the
arguments. I'd still tag a road `highway=motorway` if it's built almost to
Interstate standards (both cross traffic and opposing traffic fully
grade-separated with all entry and exit via ramps).

The class-2 roads often end short of urban centers.  For instance, the
one-way pair that carries NY 13 through the center of Ithaca is class 3.
This is understandable from the routing perspective; for instance, it
encourages drivers to bypass Manhattan unless their trip starts or ends
there.  There is also a glitch or two - as with any data set. In the Ithaca
example, one block of West State Street between the one-way pair is
inexplicably marked as class 2.  I suspect this, and the downgrading of NY
13 south of town where it splits very briefly into a one-way pair at the
NY34/96 junction, are simple data entry errors.  I think that all of these
issues could be resolved with a topology check: if a trunk's classification
dead-ends within a couple of miles, say, of another trunk in the same route
relation, or contains routing islands, flag that bit for manual patchwork.

On the other hand, it might make sense for a trunk to end a little bit
short of a city center if it carries significant traffic into and out of
that city, but is unlikely to be a significant conduit for intercity
traffic not visiting that city. I-95 across the extreme northern end is
just about the only case in Manhattan where a freeway or trunk road carries
traffic for which New York City is not a port of call.

The odd quad-carriageway Queens Boulevard / NY 25 is merely a class-3.  It
makes sense, I suppose, given that the ten or twelve lanes really just
barely carry the local traffic.

Following the New York State classifications for New York roads, except as
necessary to patch topological inconsistencies, would deflate most
arguments that the classification, at least here, is inherently subjective
- it's at least the subjective judgment of the arm of the government that's
responsible for the upkeep of the highways.

The result looks decently connected if a bit sparse. What do others think
here?  http://kbk.is-a-geek.net/attachments/20210524/NY-class-1-2.png -
blue is class 1 (essentially all `motorway` except for the missing part of
NY 17), red is class 2 (some of these are also motorways, but could
disappear at low zoom; the rest are the trunks).

-----------------------------------------

(Supplementary details follow.)

>From the metadata: (
http://gis.ny.gov/gisdata/supportfiles/Streets-Data-Dictionary.pdf):

> ACC: Arterial Classification Codes (ACCs) categorize roads according to
the level of travel mobility that
> they provide in the road network. Mobility refers to the volume of
traffic that a stretch of road carries and the
> length of trip that it serves. Roads at the highest level of mobility
serve the greatest number of trips and the
> longest trips. Conversely, high-mobility roads provide the lowest level
of access to property. Low-level, local
> roads serve that function.

> This system uses a six-level system, with 6 as the lowest level, 1 as the
highest. A list of the Arterial
> Classification Codes is in Table 2 below. Ascending through the levels,
each step represents an increase in
> relative importance to routing – an increase in the number and length of
routes using the road. In general, a
> step up also represents an increase in traffic-volume capacity of the
road, an increase in vehicle operating
> speed, and a decrease in travel time. (This system is similar to, but not
tied to, the Federal Highway>
> Administration’s Highway Functional Classification System.)

> The primary use of ACCs is in automated routing. Using ACCs, a routing
program calculates the maximum use
> of the highest-level roads that are appropriate to the scale of the
desired trip. This is analogous to the route
> planning of a typical driver, who uses the highest-speed road available,
within the geographic range
> established by the origin and destination points. The hierarchical nature
of the ACC levels allows for more
> efficient access to relevant routing networks for a given route, and in
turn reduces system requirements.
>  The implementation of ACC also supports its usage for map rendering.
Using ACC as a cartographic tool
> allows for a variety of enhancements including:
>    1. The display of “important” roads.
>    2. Reduction of line density and visual clutter based on scale of map
>    3. "Visual Routing" on paper maps (the end user chooses a route based
on ACC display)
>    4. Effective zoom layering in digital applications

The table for 'arterial classification' is complicated and appears on page
15 in the document linked above.

Kevin's summary of ACC's as they appear actually to be used:

1. Most major through-roads for interstate commerce.  (Two-digit
Interstates, plus a handful of similar roads such as NY 17, the Berkshire
Spur, I-495 east of the Cross Island Parkway interchange, I-390, I-684 and
the Hutchinson River Parkway.  All of the ones I observe in New York are
properly `highway=motorway`, with the sole exception of the short
non-motorway segment of NY 17 between Deposit and Hancock, which is also
what keeps NY 17 from being designate I-86 (much of it is signed 'Future
I-86'.

2. Many three-digit Interstates. Most state parkways. Most US Highways (4,
44, 20, 9, 9W, 209, etc.) outside the cities. NY 7 between Bennington and
Troy, between Latham and Niskayuna. NY 25 and NY 27 on Long Island.  Also,
many lesser roads in the hinterland that carry great local economic
significance.  In particular, for Russ Nelson's concern that the
classification would leave communities north of the Adirondack Park
isolated, US 11 would be included, as would NY 56 from US 11 to Massena, NY
37 from Massena to the Cornwall border crossing, and NY 812 from NY 12 to
the Ogdensburg border crossing. Addressing Jmapb's concern, Ithaca is
served by a single trunk (NY 13) that joins it to the two nearest motorways
(NY17 and the Thruway), and then a whole radiating star of class-3 roads.
In Manhattan, it's the ring road (West Street, Henry Hudson Parkway, FDR
Drive) surrounding the island, plus connections to the tunnels (Lincoln,
Holland, Brooklyn-Battery/Hugh Carey, Queens-Midtown) and certain bridges
(George Washington, Manhattan, Williamsburg, and Triborough/R.F. Kennedy),
including the crosstown arterials of 34th Street and Delancey and Canal
Streets, and roughly mile-long sections of 8th, 9th and 10th Avenues and
14th and 23rd Streets needed to get vehicles between the tunnel entrances
and the ring-road interchanges. A handful of surface streets in the
immediate vicinity of the other tunnels are included. In the outer
boroughs, almost all the freeways are class 2. (The class 1's are the
two-digit interstates, the Hutchinson River Parkway and the Throgs Neck
Bridge.)
I-495 east of the city line and the segment of the Cross Island Parkway
that connects it to the Throgs Neck Bridge are the only class 1's on Long
Island. The class 2's appear to include all motorways, plus NY 25 Truck
(not NY 25 where the truck route parallels it), NY 24 and NY 27 at the East
End.

3. Intra-state and intra-metropolitan primary roads.  These are something
of a mixed bag. Note that they do NOT include all of the numbered state
highways, and this is appropriate (some are really local connector roads or
don't really serve any fair-sized towns.  These look to be a good fit for
`highway=primary`.

4. 'Minor arterial'  These would be a good match to `highway=secondary`
except that physical characteristics enter into the state's classification
too much, creating routing islands at this level.  In any case,
primary/secondary/tertiary is not the immediate question.  I think `minor
arterial` could be a really good starting point, though, with some small
amount of manual patchwork required.

5. Pretty much everything else in the public road network: tertiary and
unclassified highways, residential streets, urban collector roads that
don't rate 'secondary highway', and so on.  The local streets.

6. Almost all class 6 roads are the access roads for apartment complexes,
commercial establishments and industrial facilities, and `highway=service`
looks to be appropriate for most of them. (For the smallest ones, the usual
arguments among 'service', 'track', 'residential' and 'unclasified' come
up. I'm not going there in this message.)

A rough idea that I think could work for New York:

Class 1 roads - All 'motorway', except that the anomalous section of NY 17
would have to be downgraded.

Class 2 roads - These should be 'motorway' if they are built to
near-Interstate standard, 'trunk' otherwise.  They need topology checks.

Class 3 roads - These are all at least 'primary'. Topology might require
upgrading some of the rest of the network to avoid routing islands at the
'primary' class.

Class 4 roads - These should all probably be at least 'secondary' -
including some only-partially-paved roads like Ulster County Route 47,
where they've pretty much abandoned the attempt to preserve a hard surface
through the mountain pass, but which provides the only access to the
Oliverea valley. There are a lot of routing islands to patch.

Class 5 roads - I'd argue that any numbered county highway (whether or not
the county signs its numbered highways, so Westchester and Nassau Counties
count!), any state touring route, or any state reference route (These last
are all unsigned, with four exceptions) rates at least 'tertiary'.
Otherwise, we're down at the 'local road' level, and we know what a morass
'unclassified', 'residential', 'service' and 'track' have become.

Class 6 roads - Usually 'service', but again we have the morass of
'lowest-level roads' to deal with.



-- 
73 de ke9tv/2, Kevin
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