[Talk-us] Prioritizing multi-banded route designators (multiple overlaps) on ways: the "Principal route designator" concept

[Peter Davies]

Same thing that I did with OSM's "I 35;I 80" around Des Moines, Iowa,
correcting it to "I 80;I 35" a few months ago.  The exit numbers and
mileposts confirm that this route has always been seen as I 80 by IADOT and
Iowa State Patrol, since its first stretches were opened in 1958-59.
http://www.iowadot.gov/50thpages/pdf/interstatemap.pdf

This is the same 12-month period in which my dad took me for a drive on
Britain's first motorway, the M6 Preston Bypass, on the week that it opened
in 1959. I was 8 years old and already knew that I would "build motorways."
 Later Sir James Drake (the project engineer) who was knighted for his
motorway building, became my top boss at Lancashire County Council and
sponsored my application to qualify as a Chartered Engineer. I remember him
shaking my hand at the County Surveyor's annual dinner in 1973.

Castle Rock has worked continuously with IADOT since 1985. When we first
set up Iowa's Condition Acquisition and Reporting System (CARS) in 1998, we
had treated the common section as I 35 (assuming a "highest system, lowest
number" rule), and Iowa DOT staff asked us to correct this to I 80.  It
remains I 80 in Iowa's CARS system to this day. We use it all across the
country as an example of a "rule exception" in discussions with other
states.

I 80 is the principal (i.e., first posted) Interstate route on the common
section of these two roads.  James and I seem to agree that such routes
should be listed first in OSM's way ref tags in order to show their special
significance.  I don't think that this needs to be in any way
controversial.  It seems to me common sense that OSM should accurately
reflect the road's signing details.

Posting roads with their "Highest system, lowest number" route first is a
good first approximation for armchair mapping, but it cannot be used to
overrule facts on the ground.

Peter Davies
Castle Rock Associates
Portland, Oregon


On Sat, Dec 21, 2013 at 11:33 PM, James Mast <rickmastfan67 at hotmail.com>wrote:

> I know awhile back I updated the ref tag on the short segment of I-77 that
> has I-74 cosigned with it from "ref=I 74;I 77" to "ref=I 77;I 74" because
> along that segment, they are using I-77's mile markers.  Plus it helps to
> know that I-77 was there long before the two I-74 signs (one NB and one SB)
> were added along it.
>
> So, at least when it comes to Interstates with 2 or more Interstates
> posted on a segment, you should always put the one that the mile
> markers/exit numbers are based off of first in the way ref tag.
>
> -James
>
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