[Talk-us] US highway classification

[Kristian Zoerhoff]

I hate it when I forget to hit Reply-All....

On Tue, May 31, 2011 at 8:54 AM, Greg Troxel <gdt at ir.bbn.com> wrote:
>
> Kristian Zoerhoff <kristian.zoerhoff at gmail.com> writes:
>
>> On Mon, May 30, 2011 at 10:41 PM, Toby Murray <toby.murray at gmail.com> wrote:
>>> On Sun, May 29, 2011 at 4:05 PM, Nathan Mills <nathan at nwacg.net> wrote:
>>>> On Sun, 29 May 2011 12:09:30 -0700, Paul Johnson wrote:
>>>>
>>>>> I'm thinking the differences between motorways and trunks are minor.
>>>>> Trunks may have intersections, motorways don't.
>>>>
>>>> That's the simple way to state my opinion. It also seemed to be the thrust
>>>> of most of the discussion on the talk page of the wiki page referenced
>>>> previously as closest to consensus (the page itself just references the
>>>> existence of the two camps and leaves it at that).
>>>>
>>>> In short, my position is simply that an end user expects a trunk road to be
>>>> identifiably different than primary or secondary. That's how it's done on
>>>> other maps, so I don't see why that's such a bad thing here.
>>>
>>> I agree with this as well. And I too thought this was a pretty widely
>>> accepted convention.
>>
>> That's one accepted convention, to be sure, but it sometimes ignores
>> the realities of where traffic goes.
>>
>> To give an example: <http://osm.org/go/ZUdwt69>
>>
>> IL 72 (the secondary at the top of the map) is a 4- to 6-lane at-grade
>> expressway; wide median, lights only every mile or so, speed limit up
>> to 55 mph. It carries a fair amount of traffic, but because it
>> parallels I 90 (a toll road here), it really only peaks at rush hour,
>> when the toll road is near capacity..
>>
>> US 20 (the trunk at the map bottom), is a 4-lane, non-divided road,
>> but it carries far more traffic than 72, as it connects the two
>> motorways at the map ends (the Elgin-O'Hare Expressway, and the Elgin
>> Bypass, which were never connected). It's not particularly
>> distinguishable from a lesser 4-lane road, aside from the absurd
>> amount of traffic it carries. If we stuck purely to the above
>> convention, 72 would be trunk, and 20 would be primary (at best).  But
>
> But what's wrong with that?  It sounds like IL 72 is a higher-class road
> in terms of the physical road, and US 20 doesn't seem to have
> almost-motorway features.   Just because a road that is properly
> labeled primary is heavily used doesn't make it a higher class; you
> certainly wouldn't label it a motorway based on traffic count.

No, but motorways are such a special case of highway I really don't
think we should use them as a basis of comparison. You're either a
motorway, or you aren't.

>> traffic flow cares more about where the road goes, not what it looks
>> like.
>
> Sure, and routers can use that.
>
>
> Probably we need to completely decouple
>
>  nominal importance in the hierarchy of road types
>  physical characteristics
>  importance to the people who use it

Haven't we already? Physical characteristics have tags (surface,
lanes, maxspeed). It's the hierarchy that seems to be the sticking
point, and that's exactly what I thought "classification" was.

--
Kristian Zoerhoff
kristian.zoerhoff at gmail.com