[Talk-us] US highway classification

[Kristian Zoerhoff]

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
traffic flow cares more about where the road goes, not what it looks
like.

-- 
Kristian Zoerhoff
kristian.zoerhoff at gmail.com