[Talk-us] [Talk-us-newyork] Highway classification guidelines for New York State

[Minh Nguyen]

Vào lúc 15:05 2021-09-16, Eric Patrick đã viết:
> Code for OSM routing engine which can be found here: 
> https://github.com/osmandapp/OsmAnd-resources/blob/0b8669d73a3befb7420a5d767a814871ae083de5/routing/routing.xml#L562-L574 
> <https://github.com/osmandapp/OsmAnd-resources/blob/0b8669d73a3befb7420a5d767a814871ae083de5/routing/routing.xml#L562-L574>
> 
> It places trunk roads underneath motorway, which makes the routing 
> engine look for the quickest route to the trunk road.

If I'm not mistaken, the code you linked to is specifically a set of 
penalties for transitioning to a lower-classed road. [1][2] This is what 
I was referring to earlier as "heuristics around avoiding the use of 
lower-classed roads once you're on a higher-classed road until you get 
close to the destination". For example, each transition from a 
highway=trunk to a highway=primary penalizes the route by 40 seconds (5 
seconds with the shortest-route engine), so the routing engine would 
prefer a different route that stays on the trunk road for another 30 
seconds based on its speed limit.

 > I believe some of
> us on this list aren't placing that high of a value on trunk roads, 
> because of the British and what they call a "trunk road." if we assigned 
> trunk roads to Primary Arterials (which is what I've been proposing), 
> the router will get to that road as quickly as possible, if the end user 
> needs to be routed onto the road. Primary Arterials exist in rural 
> areas, just as well as urban areas, so why not keep them all the same. 
> Is there really a difference between the two? I've seen the 
> argument about it would clutter cities with trunk roads. Is that 
> necessarily a bad thing? Cincinnati has a lot of its downtown areas 
> classified as Minor Arterials, while Augusta, Ga has many of its 
> downtown roads classified as Primary Arterial. If Broward County, 
> Florida had PA=trunk, there would be roughly 20 different roads, with 
> only 3 of them running through downtown Ft Lauderdale.

Actually, most of downtown Cincinnati's surface streets are classified 
as Principal Arterial by ODOT, including some streets that, at least to 
a motorist or pedestrian on the ground, are virtually indistinguishable 
from the Major Collectors the next block over. I'm not convinced they're 
so much more accessible from the freeway that they would all deserve to 
be promoted to highway=primary, let alone trunk. [3] If we're to give 
all these Principal Arterials the same highway=trunk value as the 
Appalachian Highway (SR 32), a major expressway connecting Cincinnati to 
southern and southeastern Ohio, then a renderer or router wouldn't be 
able to infer much meaning from that tag at all. [4]

In [5], I linked to another stark counterexample in the San Jose area. 
These two urban roads are both classified as Principal Arterial, to say 
nothing of rural Principal Arterials:

* Lawrence Expressway, a 10-mile-long expressway with eight lanes 
including two HOV lanes, heavy traffic every day of the week, on- and 
off-ramps, noise barriers, and a 50 mph speed limit for much of its length

* North First Street, which also runs about the same distance but has 
only two lanes, crosswalks and driveways galore, and a 30 mph speed 
limit for much of its length -- though the backbone of the city's light 
rail system does run along its median

I'm sure the DOTs have good reasons for classifying these roads this 
way. But if the reasons aren't apparent to those of us who've spent an 
inordinate amount of time debating road classification on this list and 
elsewhere, how intuitive will this system really be for a general 
audience of nonspecialist map users, especially without the aid of a 
legend? For that matter, ODOT doesn't even use FHWA functional 
classification on its own official transportation map. [6]

Maybe it turns out that some state DOTs' functional classification maps 
are more suitable for this exercise than others, but that still leaves 
the rest of us grasping for an intuitive foundation that's more reliable 
than the eyeballing that would result otherwise.

 > Each state and
> downtown area will differ, I'm 100% certain of that, but arbitrarily 
> assigning a road to be trunk because it's a US Highway doesn't do the 
> end user any justice.

I also believe that it would be a mistake in some parts of the country 
to automatically promote a U.S. route to highway=trunk, but some U.S. 
routes could qualify, with that designation as one factor among several.

[1] 
https://github.com/osmandapp/OsmAnd-resources/blob/68abc710ed87534cf87612277365e5a39717a367/routing/routing.xml#L73
[2] https://osmand.net/build_it#routing
[3] 
https://gis.dot.state.oh.us/tims/map?center=-84.50737443909436,39.10278161617497&level=14&visiblelayers=Safety:-1%7CRoadway%20Information:9%7CProjects:-1%7CEnvironmental:-1%7CBoundaries:-1%7CAssets:-1
[4] 
https://gis.dot.state.oh.us/tims/map?center=-83.65857330307729,39.011522412744945&level=10&visiblelayers=Roadway%20Information:9%7CProjects:-1%7CEnvironmental:-1%7CBoundaries:-1%7CAssets:-1
[5] https://lists.openstreetmap.org/pipermail/talk-us/2021-May/021054.html
[6] 
https://www.transportation.ohio.gov/static/About/maps/2019StateMap-Back.pdf#page=1&zoom=130,1048,1306

-- 
minh at nguyen.cincinnati.oh.us