[Talk-us] ref tags

stevea steveaOSM at softworkers.com
Tue Feb 12 19:18:45 GMT 2013

The "SR plague" is well-named.  Virtually nobody 
in California colloquially says "State Route", 
except the California Highway Patrol filling out 
tickets and Caltrans -- our California DOT -- on 
highway engineering blueprints.  I have (slowly) 
begun to back out "SR" ref tags to be the 
widespread acceptable "CA #" ref tags.  Another 
NE2 mess to clean up, mostly.  NE2 has also added 
"CR " as a prefix to California county roads, 
which already have their own quite well-defined 
nomenclature:  nine letters (A B C D E G J N R S) 
designating a regional clusters of counties 
followed by a number, such as "G2" or "S19."  To 
name any of these "CR G2" or "CR S19" (as NE2 
did) is roughly equivalent to urinating on a tree 
to say "NE2 was here."  These must have their "CR 
" prefix deleted, as well:  nobody calls the road 
"CR S19" (as NE2 has) they say "S19."

What this means is that ref tags (used at county, 
state and national levels) are and should be 
human readable, and route relations are a more 
machine parsable data structure for logically 
assembling together the various highway networks 
-- even where several exist in a single state, 
like Texas -- and assembling from existing 
infrastructure into larger wholes (at a national 
level, such as the Interstate System).

People, let us not forget that legally speaking, 
in the union of the states in North America 
colloquially known as the USA, each of the fifty 
states are sovereign, and so have the exclusive 
right to determine their own methods of naming 
highways.  The Supreme Court agrees.  For 
example, "The United States and the State of 
California are two separate sovereignties, each 
dominant in its own sphere."  (Redding v. Los 
Angeles, 81 CA2d 888, 185 P2d 430 (1947).  In 
other words, New York is just as sovereign as is 
New Zealand, South Dakota is as much a 
nation-state as South Korea.  I am not an 
attorney, but I can read.  This makes for 51 
independent jurisdictions:  the fifty states and 
the United States at a federal level.  (There 
might be "fifty-something" independent 
jurisdictions if we include DC, Puerto Rico, 
American Samoa, US Virgin Islands... but all of 
those extras are really separate areas of the 
single "federal state").  The latter (the federal 
USA) is, legally speaking, absolutely distinct 
from each of the former (the sovereign fifty 
states).  Let OSM properly reflect that.

So, in OSM, ref tags must be respectful of such 
realities, as well as be human readable. 
Concomitantly, route relations which assemble 
routes (such as "US 101") is where fancy parsing 
for renderers must happen.

I'm OK with using the USPS postal abbreviations 
for each state, even though this could be 
considered a Buck Act (4 U.S.C.S. §§ 105-110) 
"federal overlay" that potentially usurps state 
jurisdictions.  We're creating a street map here, 
not untangling the complexities of state vs. 
federal jurisdictions in North America or 
asserting that nomenclature in a mapping 
database's tagging has any legal meaning.  So, 
let's just assign sensible human meaning to ref 
tags and sensible machine parsable meaning to 
route relation tags.  This combination works to 
create all of the semantics we need for legal 
accuracy, local/county/state/federal variations, 
human readability, and logical parsability for 
software which routes or renders shields for 


>On 2013-02-11 11:30 AM, Chris Lawrence wrote:
>>I'd actually been kicking around proposing a bulk edit of ref=* tags
>>to conform them with the quasi-standard of "two-letter USPS state
>>prefix + space + route number (+ one-char suffix)?(+ space + any long
>>modifiers)" but didn't want things to devolve into a pissing match.
>>Since Mapquest seems to need ref tags to include the proper state
>>shield, and this standard is valid, even if alternative styles might
>>also be valid including the USPS prefix would seem to help.
>>Personally I'd prefer downstream consumers like MQ just use the
>>relations, like on the shield renderer at
>>http://elrond.aperiodic.net/shields/ (they also can encode proper
>>directional information, which would be very useful if OSRM understood
>>route relations) but baby steps.
>>The only drawback I can see is that many of the route numbers in
>>Georgia would disappear from the default Mapnik style, due to GDOT's
>>insistence on cosigning virtually every US-designated highway with a
>>visible state designation, which would make the shields too big to
>>render.  But this problem wouldn't affect most of the states where the
>>bare number and "SR" plague has set in.
>The "SR 123" format has been the consensus in 
>Ohio for years. Forget NE2; you'll have to 
>change the local mappers' minds first. We 
>arrived at this choice not only because "US:OH 
>123" (the wiki's suggestion originally) was too 
>long for Mapnik in most cases, but also because 
>"SR 123" is the predominant abbreviation format 
>on plain-text signage (variable message signs, 
>the occasional blade sign) and in writing 
>(traffic reports, state documents, ODOT 
>schematics, county engineers' websites, 
>Wikipedia, etc.).
>This isn't just an Ohio thing. In the Dallas/Ft. 
>Worth area, blade signs at intersections with 
>on-ramps often say "SH 123", even where the 
>highway is commonly known by a name.

(et cetera; redacted for brevity

>Minh Nguyen <mxn at 1ec5.org>

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