[Talk-us] Schizophrenic highway

Greg Troxel gdt at ir.bbn.com
Sun Sep 16 13:13:32 BST 2012

Alan Mintz <Alan_Mintz+OSM at Earthlink.Net> writes:

> At 2012-09-15 16:05, Greg Troxel wrote:
>>Charlotte Wolter <techlady at techlady.com> writes:
>> >         I'm working on US 50 near Trenton, Ill. Here's the location:
>> > http://www.openstreetmap.org/edit?lat=38.61248&lon=-89.68529&zoom=16
>> >         It looks like, at one point there were plans to turn this into
>> > a motorway. In two spots in a 25-mile stretch, intersections have been
>> > turned into cloverleafs and the highway divided. In other locations,
>> > roads that used to intersect US 50 have been turned into
>> > overpasses. There are even a couple of bridges for a second lane but
>> > no evidence of any construction work actually to build that lane. The
>> > vast majority of the highway is still two-lane blacktop.
>> >         So how does one tag this, as a primary road that just has a
>> > couple of cloverleafs?
>>My take is:
>>   motorway: truly meets interstate specs for extended periods - multi
>>   lane, no at-grade intersections.  I would not tag something as
>>   motorway when it's only sometimes motorway unless it's ~10 miles long.
> US101 near Ventura, CA, goes back and forth among
> freeway/primary/trunk over relatively short stretches. There are,
> however, "Begin Freeway" and "End Freeway" signs that tell you exactly
> which sections are motorway. This might be a DOT requirement.

That sounds like a perfect example of the most difficult case.

> SR-1 south of Oxnard is similar. Here's the location of such a sign
> going northbound: 34.112471°, -119.081681°

Where I'm coming from is that if a stretch of road that is 1 mile long
is separated and has no at-grade intersections, that doesn't make it
feel like a motorway/interstate, because part of the essence of
interstate is that one can drive for extended periods with the
expectation of not encountering an at-grade intersection.  So the
question of whether a 1-mile section of road meets specs is different
From whether that 1-mile section is part of a motorway.

Clearly one shouldn't tag sections as motorway up to intersections and
then make the intersections trunk.  So a motorway really needs at least
some grade-separated interchanges.

There's an alternative view, which is to follow begin/end freeway (not a
federal thing; I don't see those in Massachusetts) for whatever lengths,
and adjust the renderer to demote to trunk if they are short.   But I
see the motorway tag as representing the cartographer's judgement as
what should be shown to the user as being a motorway, and as a road user
I don't think a mile or two section can *be* a motorway, even if that
section meets specs.
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