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[Tarkus]

Oregon's is kind of weird, because the state has internal "highway" numbers and external "route" numbers, and the two, in many instances, don't match.  For instance, internal "Highway 144" is OR-217, and parts of OR-8 and OR-47 make up internal "Highway 29".

The actual posted route numbers, at least the established ones, seem to follow some sort of loose grid.  The north-south "primary" ones (1 and 2 digit) progress in odd numbers, generally increasing from east to west.  OR-3, the lowest is in far northeastern Oregon, and the highest one, OR-53, is near the Oregon coast.  (It is also worth noting that US 197 was at one point OR-23.)  

The east-west primary ones use even numbers and tend to progress in four "strips".  The first strip with the lowest numbers (OR-6 being the current lowest) are in western Oregon, increasing heading south (down to OR-46), then there's a strip for central Oregon, which is actually largely unused--the only ones currently are OR-66 and OR-70.  (US-26 over Mt. Hood was formerly OR-50, OR-216 was once OR-52 and part of US-20 was OR-54.)  Then there's two strips in the eastern part of the state, one finishing out the 70s, with OR-74 and OR-78, and then, farther east, OR-82 and OR-86.

There are a few aberrations in there as well.  OR-37 is in eastern Oregon, the current OR-52 is designed to be a continuation of ID-52 (it was once signed as OR-90, which makes more sense).  There's also a couple that retained the number of decommissioned US highways--OR-99, 99W, 99E, and OR-126.  OR-138 and OR-140 are also kind of oddities, but I presume they have their numbers because they are near OR-38 and a hypothetical OR-40 (if there ever was one), but extend far enough that they cross several strips.  (Both are in excess of 100 miles, making them the two longest state routes.)

The old "secondary" routes use 3-digit numbers beginning with "2".  The dichotomy of those is a little looser, and I'm not entirely sure how it works.  There are some spots that make sense (OR-211, 213, 217 and 219), and others that don't (OR-237 way out in Eastern Oregon).  They follow the standard odd=N/S and even=E/W directionality, though.

And in 2002, the legislature passed a bill calling for the signing of the remaining ODOT internal highways that didn't already have route numbers--the system on many (but not all) of those uses a two-digit "county code" for the first two digits, except in the instances in which the number conflicts with an already-posted route, in which case they make the first digit "5".  Annoyingly, those don't follow the standard odd/even system, though, as OR-131 is east-west primarily.

-Alex (Tarkus)

[PAHighways]

I'm not sure what Pennsylvania does as a state, but there seem to be a few 3-digit state routes (3ds?) that are "children" of a 2-digit route, whether state or U.S.   In my area are SR 213, 413 and 513 in the vicinity of U.S. 13; and SR 132, 232, 332, and 532 that are near to SR 32.

Pennsylvania originally clustered routes, but after years of decommissioning and renumbering, it is barely noticeable except for those examples and the x46s up near Bradford.

We have our share of state routes that fit in the interstate grid, such as 581, 283 (though there is an I-283), 378 (from a former routing of I-78).

PA 283 is actually SR 0300.  No idea why it wasn't just signed that way other than to keep some consistency with I-283 much like New York has their I-481/NY 481, I-690/NY 690, etc. pairs.

[deathtopumpkins]

Here in VA I can't for the life of me either determine a numbering system myself or find one on a website...

Did you try our VHP page on the subject?  

VA 164 has no relation whatsoever to I-64 or any I-x64s, though it theoretically could become an I-164 in the future.  It's simply a continuation of earlier numbering policy...there's been a VA 164 of some sort in the Hampton Roads area since 1933.

No I did not... keep forgetting that site exists. I've bookmarked it now. 

And seriously? I heard when they built the Western Freeway (VA-164) it was slated to become I-164. But another example that can be used instead is 895 or 195 in Richmond. 195 I know is a continuation of I-195.

[US71]

Arkansas seems to just slap a number on most highways, except AR 471, AR 463, AR 365, AR 367 and a few others, but these are old alignments of US Routes. Otherwise, it seems haphazard.  At one time, there might have been a logical system, but there doesn't seem to be one now.

3di's, you have 540 which was the first 3di, 430, 630, 530 and 440. Since Memphis has I-240, maybe Arkansas decided not to use that number.

[Urban Prairie Schooner]

Louisiana's current state highways 1 to 1241 date to 1955. They were all designated in one bill (Act 40 of the 1955 La. Legislature Extraordinary Session). Higher numbers (with the exception of 191, designated 1980) were created later.

A basic separation is that between the primary "class A" and secondary "class B" (1-185) and the farm to market "class C" roads as they were defined in 1955 (300-1241). (This A-B-C system to legally classify roads is no longer used by the state; La. switched to the standard road function classification system ca. 1979.) Though parts or all of some roads within the 1-185 range were classified as C roads, all roads 300 and up were defined as farm to market. I presume that the missing range of numbers (notably any numbers in the 2xx range) which was left unused between where the A and B class designations end and the C road designations pick up was for potential use as a future expansion area for primary and secondary designations.

Though there seems to be no pattern to the numbering of highways, upon careful observation some numbering patterns are observable. The first 25 SRs are all generally long roads and were numbered on a grid system (roughly speaking, one for the western part of the state and another for the southeast), with evens E-W and odds N-S (this is obvious if you look at the single digit SRs). Above that, the primary tendency is clustering, especially apparent in the Class C routes (SRs 300-1241) and even more so as you go up the sequence. For instance, the LA 7x routes are located largely in the region south and west of Baton Rouge, the 13x routes are in northeast La., and in St. Tammany Parish routes a cluster of 108x routes are located within a few miles of each other. A few outliers exist to the pattern such as LA 72 and LA 141, which are located far from the "zone" where one would expect them to be.

As routes were added from 1955 onward, the state apparently picked a random number (3000) and worked sequentially from there. This would explain why we have major highways and even freeways with high route designations that are unheard of elsewhere in America, or where they do exist are usually assigned to very minor roads.

Around 2000, the state began to supplement 3xxx routes with 12xx routes starting from 1242 (picking up directly after the last number used in the 1955 sequence), and it would appear that the newest state routes are actually being numbered in this range. I guess the state was reticient to crack the 3300 barrier.  

The hyphenated routes are interesting, and they get their own explanation contained herein:
http://urbanprairiewasteland.blogspot.com/2008/05/facts-about-louisianas-highway-system.html

[DrZoidberg]

 Wisconsin always seemed to have a method to the madness of their county highways.  Generally, the county would have a couple of "primary" county routes (ex. "J) several "secondary" county highways (ex. "JJ" or "JF") and even a few 3dis  (I think there is a county VVV near Lambeau Field)

[mightyace]

Wisconsin always seemed to have a method to the madness of their county highways.  Generally, the county would have a couple of "primary" county routes (ex. "J) several "secondary" county highways (ex. "JJ" or "JF") and even a few 3dis  (I think there is a county VVV near Lambeau Field)

Have you ever found any county sign multiplexes that spell words?

[ctsignguy]

I recall reading that at one time Ohio used some form of a cluster pattern in their original signages....here is the source

http://pages.prodigy.net/john.simpson/highways/expls.html

[tdindy88]

Growing up in Indiana, I am used to a grid system for the state routes, which reflects the same grid as the U.S. Highway system, with SR 2 in the north, SR 1 in the east, SR 66 in the south and SR 71 in the west. But, like the regular U.S. and Interstate system, there are some highways that don't fit the grid correctly, though the system still is pretty useful.

[roadfro]

Nevada's current state route numbering system has routes in a former road classification scheme which was completely renumbered in 1976.  The road classifications were not limited to state owned; several locally-maintained city streets and rural highways were assigned numbers in this system.  The designations were based on the road type and where primary funding sources came from:

• Federal Aid Primary (FAP)/Federal Aid Interstate (FAI): U.S. Highways and Interstates, numbered to match the U.S Route or Interstate Route number
• Federal Aid Secondary (FAS): roads of regional importance, numbered 100-499
• Federal Aid Urban (FAU): roads of importance in designated urban or small-urban areas, numbered 500-699
• State Aid Routes (SAR): secondary roads of regional importance, numbered 700-899

The numbering of routes were clustered by county or urban area, with number blocks progressing through the county or city names alphabetically and leaving room for expansion. Thus, Carson City (an independent county) had FAS's in the low 100s and SAR's in the low 700's, while White Pine County had FAS's in the high 400's and SAR's in the high 800s.  The situation was similar with cities, Boulder City starting at FAU 500, Las Vegas having FAU's in the mid-high 500s & low 600s, and Reno-Sparks having FAU routes in the mid-high 600s.  In most instances, the numbers were assigned as one progressed throughout the county or the city (south to north, east to west, etc.--it wasn't consistent, except that the Las Vegas FAU routes were mostly assigned in a grid pattern).

If a road were a state maintained facility, it would be assigned a state route number matching its FAS/FAU/SAR designation.  The problem with this system is that a road's classification could change, and NDOT highway logs from the 1980's indicate this.  For example, Rainbow Boulevard in Las Vegas was assigned to both FAS 153 and FAU 595.  As a state maintained roadway, the state route designation of Rainbow was listed in those log books as SR 153.  However, as the Las Vegas area grew in the 80's, more of the road became urban and mileage was transferred to FAU 595. 

I'm not sure exactly what happened, but it would seem that this system grew too cumbersome to keep up with.  By 1991, the state abandoned the Federal/State Aid system of routes, or at least no longer shows these in their official state highway logs.  Any NDOT-maintained roadway after this time kept the Federal Aid or State Aid number it had been assigned previously as its State Route number, with some exceptions (Rainbow Blvd became SR 595).

With the abandonment of this system, I'm not sure how new state route numbers are assigned--there have been two new routes added to the system since then (that I know of), and they both fit withing the previous number system.  One route (SR 146) in Henderson was partially reassigned (to SR 546), but the new number was probably its old FAU number.

[Alps]

I did not see NJ's numbering system explained here.  It's simpler than it looks.  1-10 are in the northeast part of the state, 10-20 have intermixed but are just outside that range, then 20-30, 30-40, 40-50, 50-60.  US 9W was originally NJ 1 and NJ 17/NJ 94 were originally NJ 2/8 (renumbered to match NY).  US 46 was originally NJ 6.  Suddenly, with the locations of 3, 4, 5, and 7, the pattern emerges.  9 and 11 were local roads in the Newark area.  Now, the 1's are a little tricky because a lot of them came in randomly.  But you do see 19-20-21 next to each other, and 22 was renumbered to NJ 59, and US 1 north of New Brunswick used to be 25...  Quite simply, the reason it looks like almost no pattern now is because the US highway system broke it up.

[dave19]

I'm not sure what Pennsylvania does as a state, but there seem to be a few 3-digit state routes (3ds?) that are "children" of a 2-digit route, whether state or U.S.   In my area are SR 213, 413 and 513 in the vicinity of U.S. 13; and SR 132, 232, 332, and 532 that are near to SR 32.

We have our share of state routes that fit in the interstate grid, such as 581, 283 (though there is an I-283), 378 (from a former routing of I-78).

We also have a number of state routes that were old U.S. routes of the same number, such as 611, 309, 230.

Here's a nice site regarding numbering of state routes in PA:
http://www.m-plex.com/roads/numbering.html

[Hellfighter]

In the Detroit area, the 3 big routes starting in downtown detroit were given the first 3 odd digits. Woodward became M-1, Gratiot and Fort Street for a while are M-3, and Grand River was given M-5. There are no other single-digit state routes except for those three.

[TheStranger]

In the Detroit area, the 3 big routes starting in downtown detroit were given the first 3 odd digits. Woodward became M-1, Gratiot and Fort Street for a while are M-3, and Grand River was given M-5. There are no other single-digit state routes except for those three.

Don't forget the Davison Freeway (M-8).

[The High Plains Traveler]

New Mexico, since it renumbered a significant portion of its route in 1988, has a system where all routes designated since that time are three-digit, with the first digit being the NMDOT District (1-6). Since not all routes were redesignated, however, there are a lot of one- and two-digit routes remaining, and a lot of three-digit routes that don't follow the first digit=DOT district rule. Another wrinkle is that, since 1988, there are no state route concurrencies with other routes. Thus, a short jog along another numbered road prevents a state route from being continuous.

[ComputerGuy]

I'd renumber British Columbia to once again match Washington.

[Alex]

This is not an opinion thread, its a thread about the origins or systems of each state's highway numbering system.

[national highway 1]

AZ uses a 2 digit primary, 3 digit secondary system
Eg.
87-187 287 387 487 (never posted) 587
77 177 277 377
Sometimes 3 digits are left over from historical highways:
266, 366 (from former US 666), now US 191
181 (from 81, then US 666, now US 191)
186 (from when AZ 86 went along I-10)
189, 289 - when US 89 still ran to the Mexican border
179 from when AZ 89A was AZ 79, then US 89A
These 3 digit routes do not correspond:
143, (153), 238 (yes, AZ does have a hwy 238), 347, (504, now US 64, continuing NM 504)

[bulldog1979]

In the Detroit area, the 3 big routes starting in downtown detroit were given the first 3 odd digits. Woodward became M-1, Gratiot and Fort Street for a while are M-3, and Grand River was given M-5. There are no other single-digit state routes except for those three.

Don't forget M-6 near Grand Rapids and M-8. Actually, as I understand it, Michigan "reserved" the single-digits for a superhighway system that later became the Interstates, and they started to re-assign the single-digits later. All of the numbers less than 10 have been in use at some time except M-2. M-7 became M-86, M-9 became M-99. M-4 was once M-134 in the UP, and later the Northwest Highway section of M-10. M-5 and M-6 were once assigned in the UP as well.

[oscar]

Hawaii's route numbering system has been discussed in a separate thread -- based on the Federal Aid route number system established in the "Great Renumbering" of the mid-1950s, with clustering by island, combined with "parent-daughter" numbering of two-digit primary routes and related three-digit secondary routes, and some four-digit secondary routes with more random number assignments but still clustered by island.

Alaska's twelve routes don't seem to follow much of a pattern (other than being completely out of synch with its Federal Aid route numbers), except that route 1 serves the largest city Anchorage, route 2 serves the second-largest city Fairbanks, route 3 connects Anchorage and Fairbanks, and the two newest routes (11 and 98) got the highest numbers, with the out-of-sequence 98 following the trail used by miners in the Klondike gold rush of 1898.

Both of the new states got basically "clean sheet of paper" systems, not constrained by any existing Interstate or US routes (but Hawaii left one-digit routes unassigned initially, making room for the Interstates that came later).

[national highway 1]

Hawaii's route numbering system has been discussed in a separate thread -- based on the Federal Aid route number system established in the "Great Renumbering" of the mid-1950s, with clustering by island, combined with "parent-daughter" numbering of two-digit primary routes and related three-digit secondary routes, and some four-digit secondary routes with more random number assignments but still clustered by island.

Alaska's twelve routes don't seem to follow much of a pattern (other than being completely out of synch with its Federal Aid route numbers), except that route 1 serves the largest city Anchorage, route 2 serves the second-largest city Fairbanks, route 3 connects Anchorage and Fairbanks, and the two newest routes (11 and 98) got the highest numbers, with the out-of-sequence 98 following the trail used by miners in the Klondike gold rush of 1898.

Both of the new states got basically "clean sheet of paper" systems, not constrained by any existing Interstate or US routes (but Hawaii left one-digit routes unassigned initially, making room for the Interstates that came later).

Then and again Oscar, how are 2-digit routes assigned in Hawaii?

[oscar]

Hawaii's route numbering system has been discussed in a separate thread -- based on the Federal Aid route number system established in the "Great Renumbering" of the mid-1950s, with clustering by island, combined with "parent-daughter" numbering of two-digit primary routes and related three-digit secondary routes, and some four-digit secondary routes with more random number assignments but still clustered by island.

Then and again Oscar, how are 2-digit routes assigned in Hawaii?

Beats me.  The guy who assigned most of the original numbers 55 or so years ago is probably long dead, and I was lucky to find (deep in the recesses of the National Archives) what information I did on the numbering system's origins.

Since Hawaiians generally don't give a crap about route numbers anyway, so long as each state route has a number for administrative purposes, that's good enough (except the primary/secondary number distinction is a useful signal to motorists about what kind of road quality to expect).  Anything more is just overthinking the exercise.

[Rover_0]

AZ uses a 2 digit primary, 3 digit secondary system
Eg.
87-187 287 387 487 (never posted) 587
77 177 277 377
Sometimes 3 digits are left over from historical highways:
266, 366 (from former US 666), now US 191
181 (from 81, then US 666, now US 191)
186 (from when AZ 86 went along I-10)
189, 289 - when US 89 still ran to the Mexican border
179 from when AZ 89A was AZ 79, then US 89A
These 3 digit routes do not correspond:
143, (153), 238 (yes, AZ does have a hwy 238), 347, (504, now US 64, continuing NM 504)

Don't forget AZ-389!!  While it doesn't connect to US-89 anymore (just US-89A), it does fit in with the AZ format.

As for Utah, there is no grid, but route numbers are often clustered together, like:

UT-7, UT-8, and UT-9 (all of which have a portion at least somewhere near St. George)

UT-12, UT-14, UT-17, UT-18, all of which are in SW portion of the state.  You also had UT-11 (now US-89A), UT-13 (replaced by 20 westernmost miles of I-70), UT-15 (now UT-9), and UT-19 (from Cedar City NW to Lund).  The still-existing routes are relics of a plan that initially put teen-numbered routes in the SW portion of the state.

UT-118, UT-119, UT-120, all in the Richfield area.

UT-67 (Legacy Parkway) and UT-68 (Redwood Rd.), in Salt Lake and Davis Counties

UT-43, UT-44, and UT-45, all in NE part of state (near Flaming Gorge/Vernal areas)

UT-32, UT-35, and UT-39, on the back end of the Wasatch Mountians

UT-20, UT-21, UT-22, UT-24, UT-25, UT-28, and UT-29, all roughly in mid-southern part of state

UT-87 and UT-88, in NE part of state (around Vernal)

UT-261 and UT-262, in SE part of state (UT-263 was another, being the eastern leg of UT-276)

That's about all I can think about right now.

[WillWeaverRVA]

And seriously? I heard when they built the Western Freeway (VA-164) it was slated to become I-164. But another example that can be used instead is 895 or 195 in Richmond. 195 I know is a continuation of I-195.

The number appears to have been a coincidence, as froggie said.

VA 895 was numbered as such because the way it was planned and funded meant it could not become an interstate highway, at least for as long as it remains a toll road. Presumably if tolls are ever removed, it could become I-895, but Transurban has a 99-year lease on the highway, so assuming it doesn't lose that lease somehow, we'll be into the 2100s before I-895 becomes reality in Virginia.

VA 195 was numbered as an extension of I-195 and is maintained by the Richmond Metropolitan Authority (which now signs the beginning and end of its area of maintenance - it does this with VA 76, too).

VA 785 is a placeholder for I-785, should it ever come into being in Virginia. It isn't signed, although "Future I-785" is.

According to the VHP, back when dinosaurs ruled the earth, three-digit state highways in Virginia were usually spurs of two-digit routes (sometimes one-digit routes, which caused confusion), and seem to have been numbered in the order of their creation - the first spur of VA 30 was VA 301, the second was VA 302, etc. This could extend past 10 - the 10th spur of VA 10 was VA 1010, and there were also a VA 1011 and a VA 1012. A spur of a spur (the first VA 311, which is now part of VA 54) got numbered as VA 3111, one of the highest numbered primary routes ever to exist.

The only current rule seems to be that primary/U.S./interstate routes cannot duplicate secondary route numbers, even though this probably isn't even a rule at all - it's just hard for this to happen since the SR's start at 600. There is no SR 895 in Chesterfield County (Henrico has no SR's). There was not a SR 664 in Suffolk when Suffolk still officially had SR's, but there IS a SR 785 in Pittsylvania County, though I'm not sure VA 785 enters the county.

[dave19]

Excellent site regarding PA route numbering:
http://www.m-plex.com/roads/numbering.html