AARoads Forum

Do any states follow a grid type system with their state highway systems?  Kind of like the Interstate system?  Looking at maps, state highways seem more or less random, but I imagine there is some logic to them.  Maybe the number is the order in which they entered the state highway system?

The only state logic I'm really aware of is Washington, where there are a few primary routes (i.e. I-5) and highways branching off of it have a 5 prefix, such as State Highway 500, 501, etc.

Do any states have a grid system where lower numbers are in one part of the state, higher numbers located at the other end?

Illinois did start off with a general lumping of certain numbers in certain regions but it really has fallen apart.

Florida does for 1 and 2 digit highways. Low numbers east and north, high numbers west and south. 3 digit state highways are in bands - most of the 5xx roads are between SR50 and SR60 for instance.

From what I remember, Indiana also followed a grid system, only with 3-digit routes being related to the parent 1 or 2 digit route (526 intersecting 26 for instance).

Washington has a far more complicated grid than just the spur numbering- the north south routes increase from west to east- 3 is the westernmost and 31 is the easternmost, the exception being SR 19. US-101 is functionally SR 1, US-97 is SR 15, and US-395 is SR 29 (and therefore does break the grid in a couple spots.)

East west routes increase from  south to north in the western part of the state, and then again in the eastern part- as you go north from the SW corner, you get SR 14, 4, 6, 8, 16/410, 18, 20. Then start again on the east side- 22, 24, 26, 28. 14 is the exception, but that was caused by the US-830 designation. US-12 used to be SR 14 where it wasn't 410, and that fits the grid. 10 doesn't either, but that's because it's old US-10.

The spur routes themselves increase from south to north and west to east. SR 121 is west of SR 129, and SR 500 is south of SR 548. There are several exceptions to that as the system has grown, but the 1964 system matches it perfectly.


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Wyoming numbers by county- the main routes are arbitrarily assigned numbers, but the other ones (the vast majority of the system) is by county in alphabetical order, so WYOs 10-29 are for Albany County, 30-49 are Big Horn, 50-69 Campbell, 70-89 Carbon, etc, up by 20 all the way to WYOs 450-469 for Weston County. Main roads are sometimes designated as spurs off US highways anyway- but there aren't very many primary state highways.

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Idaho clusters by region- the single digit routes are all in one part of the state, the 5xs in another, the teen routes in another, the 3xs in another. There are exceptions to this as the system has evolved (e.g. Idaho 55 and 52 in the southern part of the state), but mostly that's adhered to.

Really good information, corco! Thanks for posting that.

I'm curious about California's system.  It seems fairly random, but there are some areas with clusters of close numbers, like San Diego County.  CA 56,52,& 54 all SD County freeways.  CA 74 the Ortega Hwy, and then further south in Oceanside, CA 78.   

Further north, there is CA 58 and then south in LA County, you've got CA 60. 

Maybe there was a grid initially planned in CA?

There used to be a page on state highway grid numbering schemes--this is actually a topic that has interested road enthusiasts since the early days of MTR.  I don't know if it is still online, however.

I heard from Chris Bessert at a roadgeek meet once about how Michigan's original state routes were nubered.  The longest routes were given the lowest numbers, but no number lower than 10 so there wasn't any obvious "first" route.

John Simpson's site about Ohio's state routes speculates that the numbers were basically assigned in order, starting with the most important routes radiating from Cleveland, Cincinnati, and Columbus, then shorter routes in clusters around the state.  Actually, that sounds to me like they were just putting forth the least amount of effort necessary to get numbers assigned.

New Mexico (in 1912) used a version of consecutive numbering, in which the longest and most important routes received the lowest numbers.  NM 1, NM 2, and NM 3 all exist within their original corridors, for example, but have been greatly truncated in length because they were largely supplanted by the US highways.  New Mexico did not move to a system as such until the major renumbering of 1988, in which lengths of state highway which were renumbered to remove concurrencies (which were not allowed under new policy) had the NMDOT district number as the first digit in the new three-digit number.

You can't really tell with Kansas. You can see a potential grid pattern if you go from east to west. But it's not entirely in order (K-3 west of K-7; K-14 between K-17 and K-19), some numbers aren't in said grid (K-21) and it would appear to have been created after the U.S. routes were planned because U.S. highways are in between state routes that themselves are consecutively numbered (U.S. 83 being in between K-23 and K-25).

There appears to be no sort of pattern in the east-west state routes. K-96, specifically, has nothing to do with a grid.

The original North Carolina state highway numbering system was instituted before the US Highway numbering system.
East-west primary routes were issued x0 numbers and north-south primary routes were issued x5 numbers. The numbering of primary routes were issued in order of importance of the route. NC 10 ran all the way across the state from Beaufort to Raleigh to Salisbury to Asheville to Murphy. Daughter route numbers were issued by adding a digit to the right of the number. NC 10 had daughter routes of 100, 104, 105, etc.

When the US Highway system came into the state, the primary NC routes were assigned to US highways. NC 10 became US 70 from Beaufort to Asheville and US 19 from Asheville to Murphy. However, many of the daughter routes still exist, scattered along the route of the original NC 10.

Indiana has a rather comprehensive grid for their state highways that is based on the same numbering system as the U.S. highways with lower numbers to the north and east and working their way south and west. For instance, SR 1 is in the eastern part of the state, close to Ohio while SR 2 is in Northwest to Northern Indiana. The U.S. highways that run through the state also fit into the grid (at least some of them) with US 6, 31, 40, and 50 being in the approximate location of their respective state highways (which don't exist, i.e. there's no SR 31.) The progression of the grid can also be noticed in a few communities where nearly every highway that runs through it begins with the same number, for instance Noblesville has numbers in the 30s, Bloomington in the 40s, and Evansville in the 60s. Each of these communities are southwest of each other. Finally, there are also spurs that that numbered based on their parent route, SR 101 off of SR 1, SR 269 based off SR 69. Of course, as with the Interstate and U.S. highway systems, the grid is not perfect and you still have routes crisscrossing other routes and breaking off the grid. For a more comprehensive explanation of the system, this webpage explains it: http://www.highwayexplorer.com/NumberingSystemPage.php (http://www.highwayexplorer.com/NumberingSystemPage.php)

Quote from: OCGuy81 on November 11, 2011, 10:49:03 AM
Really good information, corco! Thanks for posting that.

I'm curious about California's system.  It seems fairly random, but there are some areas with clusters of close numbers, like San Diego County.  CA 56,52,& 54 all SD County freeways.  CA 74 the Ortega Hwy, and then further south in Oceanside, CA 78.  

Further north, there is CA 58 and then south in LA County, you've got CA 60.  

Maybe there was a grid initially planned in CA?

California's original system made some sense. All the "main" routes were assigned numbers 1-199, with every two numbers assigned to either NorCal or SoCal. So, SR-1 and SR-2 were in SoCal, SR-3 and SR-4 in NorCal, etc. After that, the numbers were seemingly ordered somewhat random, but lower numbers were in populated areas. You can still see this today, how CA-2 is in L.A. and CA-4 is in Stockton.

However, the introduction of the US Route and Interstate system caused a lot of old numbers to be changed/removed, and then the 1964 renumbering further changed things. Some routes, such as 2, 4, 19, 20, 120, etc. are still around in almost exactly their original alignments. Others, such as 3, 7, 8, 14, etc. are from either another route system or the 1964 renumbering. (In the case of CA-3, though, its NorCal location is coincidentally consistent with where it originally would have been.)

EDIT: CA-60, 99 and 299 are so numbered because they used to be US Routes. CA-70 was once US-40 Alternate. CA-17 was once much longer, but was replaced by several x80 3di. CA-14 was once part of a longer US-6.

Delaware, Florida, and Indiana have reasonably-well defined grids. Georgia started out with one but left no room for expansion, as did (I think) Alabama and Mississippi. Pennsylvania also started with a grid of sorts but it has changed much over the years. And Washington - yeah, they tried, but is US 97 the parent of SR 150 or SR 970?

Virginia's current system started off based on VDOT's districts. Over the years the numbers have been scattered across the state due to renumberings and elimination/reassignment of corridors.

Quote from: NE2 on November 11, 2011, 03:41:04 PM
Delaware, Florida, and Indiana have reasonably-well defined grids. Georgia started out with one but left no room for expansion, as did (I think) Alabama and Mississippi. Pennsylvania also started with a grid of sorts but it has changed much over the years. And Washington - yeah, they tried, but is US 97 the parent of SR 150 or SR 970?

I guess it's technically both: US-97 is apparently SR-15, so SR-150 would be the first spur, and then SR-970 is also a spur, but using the US-97 signage. Not consistent, but they seem to work out the same way.

QuoteAnd Washington - yeah, they tried, but is US 97 the parent of SR 150 or SR 970?

They got lazy- in the initial renumbering US-97 acted as SR 15 and US-395 acted as SR 29 for spur purposes. Subsequent changes and realignments switched the 3dis to 97x and 39x. I have no idea why they  switched, but in the 1964 grid there were no 97x or 39x routes.

Quote from: Quillz on November 11, 2011, 02:54:22 PM

Quote from: OCGuy81 on November 11, 2011, 10:49:03 AM
Really good information, corco! Thanks for posting that.

I'm curious about California's system.  It seems fairly random, but there are some areas with clusters of close numbers, like San Diego County.  CA 56,52,& 54 all SD County freeways.  CA 74 the Ortega Hwy, and then further south in Oceanside, CA 78.  

Further north, there is CA 58 and then south in LA County, you've got CA 60.  

Maybe there was a grid initially planned in CA?

California's original system made some sense. All the "main" routes were assigned numbers 1-199, with every two numbers assigned to either NorCal or SoCal. So, SR-1 and SR-2 were in SoCal, SR-3 and SR-4 in NorCal, etc.

(In the case of CA-3, though, its NorCal location is coincidentally consistent with where it originally would have been.)

Actually, 1 I don't think was considered in the socal/norcal scheme per se, as it has always had segments in both halves of the state (I usually consider the straight-line county border between Monterey and San Luis Obispo as the divider).

From the first few numbers, the 1934 numberings:

2 - still in the original spot it was, Santa Monica Boulevard and Angeles Crest Highway, though west segment was an extended portion of US 66 from 1937-1964
3 - today's Route 1 from Ventura to San Juan Capistrano

4 - same spot
5 - today's Route 35 in the Bay Area

6 - now-defunct state route along Bolsa Avenue in Orange County
7 - today's I-405, Route 14, and then US 395 north of Inyokern

8 - today's Route 88 in Stockton
9 - most of today's route + routes 236, 85, 237, 262, 238

10 - what later became Route 42, I-5 (at one point US 101) from the LAX area to Anaheim
11 - today's I-110 and Route 110

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Some of the post-1964 clustering seems to be sequential assignment of routes to an area, particularly 236, 237, and 238 all being former portions of Route 9.  The Orange County tollways going (231), 261, and 241 fits this too, though much later on.

Québec's entire autoroute and provincial route systems are numbered in a grid, using rules inspired by the U.S. and Interstate systems. Autoroutes use the same numbering scheme as Interstates, including the 3-digit routes, and conventional provincial routes use the even-odd rule and numbers raising from west to east and from south to north as well. However, all of them have 3 digits so they don't clash with autoroutes, so spurs are either unnumbered or use a different number. 100s are primary roads, 200s are secondaries south of the St. Lawrence River, 300s are secondaries north of that river. 400+ numbers are reserved for 3 digit autoroutes. Tertiaries and other arteries have 5-digit numbers and are unsigned.

The province's entire road grid is rotated counterclockwise and is aligned on the St. Lawrence River. So as far as roads are concerned, north is actually northwest, east is northeast, south is southeast and west is southwest. Except maybe way up north. Even small country roads in the middle of nowhere on the South Shore are aligned that way.

As NE2 mentioned above, Georgia started out with a rough grid system for its initial routes.  East-west routes had even numbers, going from 2 in the north to 40 in the south.  North-south routes had odd numbers, starting with 1 in the west and going to 25 in the east, then working back to the west through south Georgia up to 39.  Most of these routes are still in place today (Georgia overlaid US routes onto the existing system instead of replacing state routes).  After those initial 40, new route numbers were assigned roughly in chronological order (except for the 400 and 500 series).

Quote from: realjd on November 11, 2011, 10:30:55 AM
Florida does for 1 and 2 digit highways. Low numbers east and north, high numbers west and south. 3 digit state highways are in bands - most of the 5xx roads are between SR50 and SR60 for instance.

Also, 2di routes tend to span entire counties, usually multiple counties, compared to most 3di routes. 2di Routes ending in zero usually run from coast-to-coast, although routes like 20 and 30 seem to be exceptions. (In fact, the 3x even routes are mysteriously missing). x00 routes like 100, 200, 400, 500, 600, 700 are diagonal routes, but generally they're secret numbers, save the first two, and 400 and 700 only exist as standalone routes for a small portion of their lengths.

Quote from: formulanone on November 12, 2011, 12:07:16 PM

Quote from: realjd on November 11, 2011, 10:30:55 AM
Florida does for 1 and 2 digit highways. Low numbers east and north, high numbers west and south. 3 digit state highways are in bands - most of the 5xx roads are between SR50 and SR60 for instance.

Also, 2di routes tend to span entire counties, usually multiple counties, compared to most 3di routes. 2di Routes ending in zero usually run from coast-to-coast, although routes like 20 and 30 seem to be exceptions. (In fact, the 3x even routes are mysteriously missing). x00 routes like 100, 200, 400, 500, 600, 700 are diagonal routes, but generally they're secret numbers, save the first two, and 400 and 700 only exist as standalone routes for a small portion of their lengths.

What is interesting is that FL 44 goes across the state and FL 40 does not!  FL 40 is the only two digit route ending in  zero that does not cross the entire penisula as FL 30 does not even make it in the penisula.  FL 30 is secret number for the East- West part of US 98 and its eastern terminus is at Perry at the east end of the panhandle.  However, the route number 40 goes across the penisula as west of US 41 where SR 40 ends to the west, Citrus County has a road numbered CR 40 that continues to US 19.

And CR 40 used to be SR 40. (Additionally, SR 40 initially went from Barberville to DeLand on SR 15 and then east on what's now SR 44 to New Smyrna Beach.)

Pennsylvania originally had something like that - PA 1 became mostly US 30, PA 3 is now mostly US 22, PA 5 is now with exceptions US 322, PA 7 is now US 6, and PA 9 is now US 20. PA 2 mostly became US 611, PA 6 is now US 219, and PA 8 remains north of Pittsburgh.
Check out www.m-plex.com/roads/numbering.html for detailed explanation.

For the pre-2000 routes, primary Oregon routes are generally numbered lowest north to highest south for east-west routes, and lowest west to highest east for north-south routes. Groupings of primary east-west routes are roughly divided into  three strips: 6 through 46 in Western Oregon, 58 through 70 in Central Oregon, and 74 through 86 in Eastern Oregon (78 appears to break the rule, but there are technically two strips if you count 74 and 78 as a separate strip). Secondary highways starting with 201 seem to be in order of creation, i think, though if someone else knows how they were numbered, please let me know!

Other state routes that don't fit this grid:
52, a continuation of ID-52 (Originally, OR-52 was what is now OR-216 which fits in the grid)
99, 99E, 99W, 126 in which they were originally US routes
138, which incidentally matches the internal highway number for the portion of the route from Roseburg to US-97
140, as part of the Winnemucca-to-the-Sea Highway and continues as NV-140

Post-2000 routes match up with the internal highway number, and are grouped according to the ODOT region they fall in:
100-series numbers - Region 1 (Portland Metro)
200-series numbers - Region 2 (Western Willamette Valley to the Coast)
300-series numbers - Region 3 (Southwestern Oregon)
400-series numbers - Regions 4 and 5 (Central and Eastern Oregon)
500-series numbers - reserved for duplicated route numbers (simply adding a 5 to the first digit or changing the first digit into a 5)

Quote from: luokou on November 12, 2011, 06:46:50 PM
For the pre-2000 routes, primary Oregon routes are generally numbered lowest north to highest south for east-west routes, and lowest west to highest east for north-south routes. Groupings of primary east-west routes are roughly divided into  three strips: 6 through 46 in Western Oregon, 58 through 70 in Central Oregon, and 74 through 86 in Eastern Oregon (78 appears to break the rule, but there are technically two strips if you count 74 and 78 as a separate strip).

I think that was the idea.  I always thought there were 4 strips, not 3, for that very reason.

The pattern is even clearer if you throw in the state routes that no longer exist:
- OR 2 (now US 26 west of Portland);
- OR 14 (now OR 22 between Grand Ronde and Hebo);
- OR 26 (now US 20 between Albany and Newport);
- OR 50 (now US 26 between Portland and Madras);
- OR 52 (the 1st incarnation, now the western half of OR 216);
- OR 54 (now US 20 between Albany and Vale);

North-souths no longer with us:
- OR 15 (now OR 37, but it was US 395 in between);
- OR 23 (now US 197)

QuoteSecondary highways starting with 201 seem to be in order of creation, i think, though if someone else knows how they were numbered, please let me know!

I have the 1936 Oregon Highway Map, the first year they appeared, so that shows the original system.  There seemed to be a general tendency that the evens increased as you moved south and the odds increased as you moved west, but it wasn't perfect.  So many routes have been deleted and added randomly since then that any order the grid might have had has now been swamped by that randomness.

QuoteOther state routes that don't fit this grid:
52, a continuation of ID-52 (Originally, OR-52 was what is now OR-216 which fits in the grid)

Worth mentioning that current OR 52 was originally OR 90, which did fit the grid.

Quote138, which incidentally matches the internal highway number for the portion of the route from Roseburg to US-97

That was intentional and a fairly recent change; prior to that, it was North Umpqua Hwy #73 and East Diamond Lake Hwy #425

Here's a trivia question for you: prior to the OR 138 change and the advent of the 2002 routes, where were the only places in Oregon where a route had the same number as its hidden highway designation?

QuotePost-2000 routes match up with the internal highway number, and are grouped according to the ODOT region they fall in:
100-series numbers - Region 1 (Portland Metro)
200-series numbers - Region 2 (Western Willamette Valley to the Coast)
300-series numbers - Region 3 (Southwestern Oregon)
400-series numbers - Regions 4 and 5 (Central and Eastern Oregon)
500-series numbers - reserved for duplicated route numbers (simply adding a 5 to the first digit or changing the first digit into a 5)

It's actually a little more specific -- they are related to the county the highway originates in, starting in the NW corner and working south, then east.  Hence, Clatsop County hwys are #10x, Columbia County's are #11x, etc, up to Malheur County's #45x's. (Note that Oregon has 36 counties.)  That generally matches the ODOT regions, but not like what you wrote.  For example, Marion County has the 16x's, Lincoln County has 18x's and Polk County has 19x's, and those are all region 2, not Portland Metro!

Then there seem to be some very recent numbers applied to spurs/loops in the 48x's and 49x's.  None of these correspond to any route numbers.

Connecticut originally had a system where it numbered primary state highways as 1xx and secondary state highways as 3xx (with one and two digit numberes being reserved for New England's interstate routes). But then the state went and renumbered basically everything and now there isn't much particular rhyme or reason to the numbering - although there is still a general trend that the lower the number, the more major the route, and there is still sometimes a tendency to group things somewhat (best example is how CT 77, 79, 81, 83, 85, and 87 are all north-south routes which run roughly parallel to each other in that order).

There is still a solid system for the unsigned routes, though. 4xx routes lead to a state-owned facility of some sort (park, airport, train station, etc.). 5xx, 6xx, 7xx, and 8xx are in ConnDOT regions 1 through 4, respectively (though the region borders don't match up with county lines at all and if you look at them on a map there is no apparent sense to why the borders were drawn the way they are). 9xx routes are just really short bits of road that are state maintained.


New York, again, has no real pattern to its signed routes, but the unsigned ones have a system. In this case, all unsigned "reference routes" are three digit numbers beginning with 9 followed by a letter. The tens digit is the region number (so, for instance, route 983D is in region 8).

Quote from: apeman33 on November 11, 2011, 12:01:21 PM
You can't really tell with Kansas. You can see a potential grid pattern if you go from east to west. But it's not entirely in order (K-3 west of K-7; K-14 between K-17 and K-19), some numbers aren't in said grid (K-21) and it would appear to have been created after the U.S. routes were planned because U.S. highways are in between state routes that themselves are consecutively numbered (U.S. 83 being in between K-23 and K-25).

There appears to be no sort of pattern in the east-west state routes. K-96, specifically, has nothing to do with a grid.

Actually, K-21 was in your grid... it was the original designation of US 283.

Also, remember that US 183 and US 281 were origionally designated as K-1 and K-8, respectively. Oh, and don't forget that K-99 and K-177 were originally K-11 and K-13

I don't think TX has ever had a definite route allocation system, especially since the late 1930s.  From the best I can tell, without proper research, it looks like from older maps I've seen, that 1- and 2-digit numbers were generally assigned to longer routes, while 3-digit numbers were given much shorter ones.  Other than that, I've seen no E-W/N-S arrangements, no incremental assignments, nor even-odd arrangements among the placements.  The closest thing to a parent-child (a-la the US highways) instance was (and still is) TX 236 turning off of TX 36 in central TX, west of I-35.  I've never heard whether this was intentional, or not.

Usually the state is pretty good about not putting a state highway near a same-numbered US, Interstate, or other numbered highway, with a couple of known exceptions.  TX 70 crosses US 70 (and US 62) in Matador, while FM 121 in Grayson County (north of Dallas) comes very close to TX 121 in Collin and Fannin Counties.  I would think, as big as TX is, that there's plenty of room to avoid any possibility of confusing same-numbered intersections, including the 2 examples above.  Now as for the future intersection of I-69 with US 69 near Lufkin in a few years, ummm, well, let's just say they didn't ask my opinion about it first  :cool:

Quote from: Duke87 on November 13, 2011, 12:10:43 AM
New York, again, has no real pattern to its signed routes, but the unsigned ones have a system. In this case, all unsigned "reference routes" are three digit numbers beginning with 9 followed by a letter. The tens digit is the region number (so, for instance, route 983D is in region 8).

According to wikipedia (http://en.wikipedia.org/wiki/1930_state_highway_renumbering_(New_York)), NY's route numbers were assigned in clusters based on geographic location, though that's not followed today.

Quote from: xonhulu on November 12, 2011, 08:17:48 PMHere's a trivia question for you: prior to the OR 138 change and the advent of the 2002 routes, where were the only places in Oregon where a route had the same number as its hidden highway designation?

Both of them involve U.S. 26:  From the Ross Island Bridge east to the junction with Oregon Route 35 is Highway 26.  (U.S. 26 becomes the Warm Springs Highway 53 southeast from there, while Mt. Hood Highway 26 follows Oregon Route 35 north to Hood River.)

U.S. 26 west of downtown Portland is the Sunset Highway 47.  Between Banks and Manning, Oregon Route 47 is multiplexed with U.S. 26.  North of Manning and in Banks south to (but not beyond) Forest Grove, however, Route 47 is the Nehalem Highway 102.

Quote from: sp_redelectric on November 13, 2011, 11:41:57 AM
Both of them involve U.S. 26:  From the Ross Island Bridge east to the junction with Oregon Route 35 is Highway 26.  (U.S. 26 becomes the Warm Springs Highway 53 southeast from there, while Mt. Hood Highway 26 follows Oregon Route 35 north to Hood River.)

U.S. 26 west of downtown Portland is the Sunset Highway 47.  Between Banks and Manning, Oregon Route 47 is multiplexed with U.S. 26.  North of Manning and in Banks south to (but not beyond) Forest Grove, however, Route 47 is the Nehalem Highway 102.

Good job!  You got both of the cases I was thinking of, and I'm pretty sure there were no other examples.  Both are coincidences, AFAIK, especially the first example, since when the Mt Hood Hwy #26 was designated in 1917 there's no way they could've foretold US 26's creation in 1926 or its 1952 extension to Oregon.  The OR 47 duplex with Sunset (Wolf Creek) Hwy #47 is much older, I believe, dating to the creation of the Oregon Route System in the early 30's.

QuoteNew Mexico (in 1912) used a version of consecutive numbering, in which the longest and most important routes received the lowest numbers.  NM 1, NM 2, and NM 3 all exist within their original corridors, for example, but have been greatly truncated in length because they were largely supplanted by the US highways.  New Mexico did not move to a system as such until the major renumbering of 1988, in which lengths of state highway which were renumbered to remove concurrencies (which were not allowed under new policy) had the NMDOT district number as the first digit in the new three-digit number.

NM-1 disappeared after 1927 in favor of U.S. 85, when the "modern" New Mexico route system was established to accommodate the U.S. routes. It reappeared in the early-1970s after completion of I-25 between T or C and San Antonio, when it was assigned to old U.S. 85 in that lightly traveled stretch. NM-2 continued in existence until the early 1930s when U.S. 285 was established, disappeared for a couple of decades, then was assigned to a stretch of old U.S. 285 between Roswell and Artesia. This road was also designated U.S. 285 Alternate.  I saw both NM-1 and NM-2 posted in the mid-70s when I lived in New Mexico; I know, Jonathan, you have cited documentation that New Mexico assigned NM-1 in 1988, but it was posted long before that.

NM-3 has been in continuous existence since the 19-teens, but no piece of present-day NM-3 exists along the original NM-3 corridor. That original route is U.S. 70 east of Las Cruces, U.S. 54 to Tucumcari, and old U.S. 66 east of there. One original route that I'm pretty sure exists today exclusively along its historic alignment is NM-41.

One big weakness with the new system of first digit for DOT district is that it isn't consistent; many routes continue to carry their pre-1988 designation, so there is no perceived value in clustering of the routes that were renumbered or newly designated at/after that time.

Quote from: xonhulu on November 12, 2011, 08:17:48 PM
It's actually a little more specific -- they are related to the county the highway originates in, starting in the NW corner and working south, then east.  Hence, Clatsop County hwys are #10x, Columbia County's are #11x, etc, up to Malheur County's #45x's. (Note that Oregon has 36 counties.)  That generally matches the ODOT regions, but not like what you wrote.  For example, Marion County has the 16x's, Lincoln County has 18x's and Polk County has 19x's, and those are all region 2, not Portland Metro!

Then there seem to be some very recent numbers applied to spurs/loops in the 48x's and 49x's.  None of these correspond to any route numbers.

Very enlightening! I didn't know the post-2000 numbers had finer divisions as such. I did notice that the numbers generally tended to fit in ODOT regions, but I was hastily looking over the official map and doing some broad matching before running off to work. Thanks for the information!

QuoteFrom the first few numbers, the 1934 numberings:

2 - still in the original spot it was, Santa Monica Boulevard and Angeles Crest Highway, though west segment was an extended portion of US 66 from 1937-1964
3 - today's Route 1 from Ventura to San Juan Capistrano

4 - same spot
5 - today's Route 35 in the Bay Area

6 - now-defunct state route along Bolsa Avenue in Orange County

The original CA-6 actually ran along what later became CA-26, Olympic Blvd., except that it used Pico Blvd. at Santa Monica. The short-lived designation for Bolsa Avenue in Orange County was CA-26. Obviously, CA-6 was renumbered when U.S. 6 was extended into California in 1936.  If you look at the 1934 L.A. area map you can easily see the system of adjacent routes separated by 4, which was the original numbering scheme throughout California: 2, 6, 10, 14, 18, 22 and 26; and north-south: 3, 7, 11, 15, and 19. 

Quote from: luokou on November 13, 2011, 02:26:22 PM
Very enlightening! I didn't know the post-2000 numbers had finer divisions as such. I did notice that the numbers generally tended to fit in ODOT regions, but I was hastily looking over the official map and doing some broad matching before running off to work. Thanks for the information!

I should add this pattern seems to have two "bands:"  west of the Cascades and east of them.  Within each band the numbers increase by county first eastward, then southward.

Quote from: The High Plains Traveler on November 13, 2011, 02:33:01 PM

QuoteFrom the first few numbers, the 1934 numberings:

2 - still in the original spot it was, Santa Monica Boulevard and Angeles Crest Highway, though west segment was an extended portion of US 66 from 1937-1964
3 - today's Route 1 from Ventura to San Juan Capistrano

4 - same spot
5 - today's Route 35 in the Bay Area

6 - now-defunct state route along Bolsa Avenue in Orange County

The original CA-6 actually ran along what later became CA-26, Olympic Blvd., except that it used Pico Blvd. at Santa Monica. The short-lived designation for Bolsa Avenue in Orange County was CA-26. Obviously, CA-6 was renumbered when U.S. 6 was extended into California in 1936.  If you look at the 1934 L.A. area map you can easily see the system of adjacent routes separated by 4, which was the original numbering scheme throughout California: 2, 6, 10, 14, 18, 22 and 26; and north-south: 3, 7, 11, 15, and 19. 

Thinking about Norcal for a second, trying to see if this applied:

4 (still in same route today)
8 (now Route 88 in Stockton)
12 (same route today)
16 (mostly same route today)
20 (same route today)
24 (truncated from its fullest extent but still exists)
28 (This, I'm curious about: it became signed route 128 but not sure the pre-1950s Route 28 ever even was signed)
32
36

don't think there ever was a state route 40

44 has been realigned significantly but still exists near original corridor

original 48 I don't think was a 1934 route

For the odds...
5 (now 35)
9 (truncated but still exists)
13 (original 13 became 17)
21 (don't think this is from 1934 though)
25 (still exists)
29 (exists)
33 (more of a cross-state route, still exists)
37 (still exists but realigned)
41
45
49
53 (was this originally from 1934?  shortened since 1964)

http://www.gbcnet.com/roads/ca_routes_1934.html

The modern CA-33 is mostly from the 1964 renumbering, though. Much of it replaced the old US-399.

Quote from: Quillz on November 14, 2011, 03:18:17 AM
The modern CA-33 is mostly from the 1964 renumbering, though. Much of it replaced the old US-399.

Not necessarily.  The portion of Route 33 north of Route 166 (to I-5) is approximately original to what the route was in 1934, and is way longer than the ex-US 399 segment ever has been.

The previous description of North Carolina's original system is not quite accurate...

The major routes in the beginning (1920 or 1921) did end in 0 but direction was not a consideration:

NC 10 EW - US 19 S of Asheville, US 70 e of Asheville
NC 20 EW - US 70 W of Asheville, US 74 E of Asheville
NC 30 NS - US 17 S of Windsor, several routes n of Windsor
NC 40 NS - US 117, US 301 n of US 117
NC 50 NS - US 1
NC 60  diag - US 421
NC 70 NS - several routes, notably US 220
NC 80 NS - US 52 S of Salisbury, US 601 N of Salisbury
NC 90 EW - US 64 E of Raleigh
These routes then had daughters in a grid:
For example, NC 10's daughters were situated in an E to W grid:
NC 11
NC 12 (now mostly US 258)
NC 13 (US 501 N of Durham)
NC 14 (now NC 86)
NC 15 (US 29 S of Salisbury)
NC 16 (US 321 Bus, etc S of Conover)
NC 17 (US 321 N of Hickory)
NC 18
NC 19 (mostly US 221)

Some x0 routes skipped numbers in their daughter schemes and x5 was not particularly special nor necessarily N-S running.

The daughters, plus the x0 routes also had 3 digit daughters which initially also were placed in a progressing grid:
NC 101
NC 102 (generally US 13 near Goldsboro)
NC 103 (now NC 119)
NC 104 (now NC 80)
NC 105 (NC 126 and abandoned route northward)
NC 106 (now NC 107)
NC 107 (US 441 n of Dillsboro)
NC 108 (now US 129 n of US 19)
NC 109 (US 64 murphy to Hayesville)

NC 20 actually had so many spurs that it used 21x numbers too.

Eventually before the state scrapped their system in 1934 they had to make exceptions like NC 31 in Mars Hill (but it had a NC 311 spur)...

The earliest NCDOT map of NC with the numbers on it can be accessed here (1922) - http://dc.lib.unc.edu/cdm4/item_viewer.php?CISOROOT=/ncmaps&CISOPTR=1802&CISOBOX=1&REC=9 (http://dc.lib.unc.edu/cdm4/item_viewer.php?CISOROOT=/ncmaps&CISOPTR=1802&CISOBOX=1&REC=9)

Mapmikey

A best example I saw of state highway numbering was old CA-30 before it was turned into CA-210. There is a spur, CA-330, east of San Bernardino.

CA-55 and CA-57 also seem be on some kind of grid. Both routes are close, hence, the close numbers and then they are both odd, going North to South.

Same for CA-56, CA-52, and CA-54 near San Diego. (Relatively) Close together and both are even as East-West routes.

Only three examples of numbering I saw that made any sense.

One that hasn't been mentioned yet is Mississippi.  Mississippi has a fairly (all things considered) uniform numbering system for their state highways.  Two notes to start with:  all north-south routes are odd-numbered while all east-west routes are even-numbered (though there's a couple routes, MS 315 in particular, that in reality break this standard).  Also, the US highway system predates Mississippi's state numbered routes, so there never was a MS 11, MS 45, MS 49, MS 80, MS 84, etc etc.

The 1/2-digit routes are also sequenced into a grid for the most part.  Odd-numbered routes begin with MS 1 in the western part of the state and increase to MS 19 in the east.  The odd MS 2x routes are a bit jumbled, but the process begins again with MS 33 in the southwest and MS 41 in the northeast (there is no MS 31).  Technically another process continues with MS 43 being west of MS 47.  The odd MS 5x routes used to exist along/near the Mississippi Gulf Coast, starting with MS 53 in Hancock County and continuing to MS 63 in the east.  When the Interstates came, old MS 55 was renumbered MS 67, old MS 57 became part of an extended MS 15, and old MS 59 became the new MS 57.  MS 69 near Columbus sort of fits this MS 5x-6x scheme.

The even routes begin with MS 2 in the north and continue to MS 26 in the south.  When the Interstates came, old MS 10 became MS 50 and old MS 20 became MS 28.  MS 22 is not an original route...it was added ca. 1950, hence why it breaks this part of the grid.  The process begins again with MS 30 in the north and continuing to MS 48 in the south, but there's a noted discrepancy here:  MS 46.  Also, MS 44 is a bit of a discrepancy, being south of MS 48, but it's not an original route and was added later.

MS 1xx routes are former US route alignments that the state wished to keep on the state highway system.   There is also a MS 2xx route:  MS 245, which is the former alignment for ALT US 45.  A MS 249 has been proposed in the Jackson area, but has not been approved by the legislature.

Mississippi's 3-digit routes are also organized geographically based on their first digit.  MS 3xx routes are in northern Mississippi, generally north of US 82.  MS 4xx routes are in north-central Mississippi (generally between US 82 and US 80), while MS 5xx routes are in south-central Mississippi.  MS 6xx routes are in the 6 counties adjacent to the Gulf Coast.

Mississippi's generally-hidden-but-occasionally-signed routes are also organized geographically:  MS 7xx routes in northern Mississippi, MS 8xx routes in central Mississippi, and MS 9xx routes in southern Mississippi.  The highest route number is MS 992 in Picayune.

Quote from: Riverside Frwy on November 14, 2011, 10:11:56 AM
A best example I saw of state highway numbering was old CA-30 before it was turned into CA-210. There is a spur, CA-330, east of San Bernardino.

CA-55 and CA-57 also seem be on some kind of grid. Both routes are close, hence, the close numbers and then they are both odd, going North to South.

Same for CA-56, CA-52, and CA-54 near San Diego. (Relatively) Close together and both are even as East-West routes.

Only three examples of numbering I saw that made any sense.

Post-1964 route clustering:

- Route 82, 84, 85, 87 all established in the Bay Area
- Routes 236, 237, 238 are all ex-Route 9
- today's Route 242 (ex-Route 24) is not far from unbuilt Route 239.
- Post-1964 Route 31 was in the same vicinity as 1950s-2005 Route 30
- Today's unsigned Route 164 (which really should just be reverted to Route 19) is in metro LA, where the original 1964 Routes 159, 163 and 165 were as well
- Routes 78 and 79 are original to the 1934 state highway system; Route 75 was added to metro San Diego in the 1940s, and Route 76 in the 1950s
- Routes 72 and 73 were added in Orange County near 1934-era Route 74
- Unbuilt routes 143 and 148 both were planned to run towards the Sacramento suburb of Elk Grove

Route 55 is original to the 1934 grid, with 57 being created in 1964.

Illinois' system started out with SBI (State Bond Issue) routes that later became the state route numbers. The first wave in 1918 were routes 1-46 and the second in 1924 involved route 47-185. I can't really tell any rhyme or reason to the numbering scheme from Rich Carlson's (http://www.n9jig.com/) descriptions, so my best guess is that the more important routes received the first Bond Issues, and therefore the lower numbers.

I don't know very much about the Iowa system, but it looks like the more important routes had the lowest numbers.

EDIT: After putting the first 15 or so IL SBI routes onto a map, I was able to determine that:

• All of the primary cross-state routes seemed to be covered on the map
• 1-3 were N-S, increasing from east to west
• 5-13 were E-W, increasing from north to south
• 4 was also N-S, but it was diagonal (became US-66)

The rest were relatively minor and, like previously mentioned, were grouped by region.

South Dakota has a very well established grid of two digit state highways that mirrors the US highway grid.  (odd numbers N-S increasing east to west and even numbers E-W increasing north to south).  They seem to have left a lot of room for expansion in that grid if they ever wanted to since they skip many numbers.
Many of their 3 digits state highways are numbered as spurs, but many others are just random.

QuoteA best example I saw of state highway numbering was old CA-30 before it was turned into CA-210. There is a spur, CA-330, east of San Bernardino.

CA-55 and CA-57 also seem be on some kind of grid. Both routes are close, hence, the close numbers and then they are both odd, going North to South.

Same for CA-56, CA-52, and CA-54 near San Diego. (Relatively) Close together and both are even as East-West routes.

CA-330 is a former piece of CA-30 which ran into the San Bernardino Mountains there. 30 was re-routed down to I-10 at Redlands before 210 came into existence. The 330 designation is analogous to CA-371, a former piece of 71. I think those are the only CA-3xx routes in California.

CA-55 is an original or nearly original numbered state highway, while 57 is a relatively new route that didn't exist before the 1960s. I don't know if that designation had been assigned at the time of the 1964 renumbering. It's possible it was selected as an available route adjacent to 55. I think the same logic applies to 52, 54, and 56 near San Diego, none of which existed before the 1960s and are probably post-1964 routes. It's a good guess the numbers were assigned (ultimately by the Legislature but proposed by CalTrans) because of their adjacency. I don't think the odd-even factor enters in since 1964, however; there are even N-S and odd E-W routes.

I'm a little intrigued by the two oddball routes in the original 1934 plan: 740 was an obvious extension of 74, separated by a piece of U.S. 395 between Elsinore and a point east of there where 395 went north (this was eventually bypassed by 395 and became 74 only); and 440, from Redding to Lassen Park even though there wasn't a 44 in the original postings. I think those disappeared within a year or two - anyone have a better map collection from this era than I?

Quote from: corco on November 11, 2011, 10:34:18 AM
Washington has a far more complicated grid than just the spur numbering- the north south routes increase from west to east- 3 is the westernmost and 31 is the easternmost, the exception being SR 19. US-101 is functionally SR 1, US-97 is SR 15, and US-395 is SR 29 (and therefore does break the grid in a couple spots.)

East west routes increase from  south to north in the western part of the state, and then again in the eastern part- as you go north from the SW corner, you get SR 14, 4, 6, 8, 16/410, 18, 20. Then start again on the east side- 22, 24, 26, 28. 14 is the exception, but that was caused by the US-830 designation. US-12 used to be SR 14 where it wasn't 410, and that fits the grid. 10 doesn't either, but that's because it's old US-10.

Minor quibble.  I'm fairly certain there are 3 strips of east/west routes, not two as you describe.

As you mention, when the current routes were numbered in 1964, US 12 was still four or five years from being extended into the state, and US 830 was still four or five years from being decommissioned.  So, in the original plan, not only did you have SR 14 further north where US 12 is today, but you also had US 830 being functionally SR 12 (example: what is now SR 141 was originally SR 121).

(Note that where you say, "US-12 used to be SR 14 where it wasn't 410, and that fits the grid," that's not true as you describe it, since it's south of SR 8 -- both the new and original versions.)

So I think there's three strips... western (SR 4, SR 6, SR 8 ), central (US 830/SR 12 (now SR 14), SR 14 (now US 12), US 410/SR 16, SR 18, SR 20), and eastern (SR 22-30, 30 being the original number for the eastern half of SR 20).

Also, you mention SR 19 as an exception added later, but SR 11 was also added slightly after the original plan, and is slightly out of the grid west of SR 9.

Quote from: The High Plains Traveler on November 14, 2011, 07:25:00 PM
440, from Redding to Lassen Park even though there wasn't a 44 in the original postings.

44 quickly became US 299, and 740 initially extended north on US 395 to Riverside. (US 395 south of Elsinore was 71.)
http://www.gbcnet.com/roads/ca_routes_1934.html

New Jersey 5xx county routes are in a  N-S grid more or less with 502 in the north to 540 in the south.  But above 540 is random.

There seems to be some clustering 20s around Newark ( 20 21 22 23 24 28),  30s radiating out of Trenton and in Monmouth and Ocean Counties( 31 32 33 34 35 36 37). 40s radiate out of Camden.. (40( now 70) 41 42 44 45 47)

But any grid to state highways seems to have been abandoned.

Quote from: deanej on November 13, 2011, 11:30:13 AM

Quote from: Duke87 on November 13, 2011, 12:10:43 AM
New York, again, has no real pattern to its signed routes, but the unsigned ones have a system. In this case, all unsigned "reference routes" are three digit numbers beginning with 9 followed by a letter. The tens digit is the region number (so, for instance, route 983D is in region 8).

According to wikipedia (http://en.wikipedia.org/wiki/1930_state_highway_renumbering_(New_York)), NY's route numbers were assigned in clusters based on geographic location, though that's not followed today.

New York's original touring routes in 1924 had odd numbers for E-W routes and even numbers for N-S routes. E-W routes had a very loose progression from north to south...excluding NY 1, which by an odd mix of design and coincidence is now US 1. The rest, NY 3, 5, 7, 9, 13, 15, 17 were pretty much in order. 11 was oddball, being north of NY 5. Then you jump back a bit for 19, 21...23 is out of place...and then 25 and 27 which are still there on Long Island.

For N-S routes, you had NY 2 and 4, then from east to west you had NY 6, 8, 10, 12, 14, 16, 18...20 was oddball...then jumping back to the east for 22, 24, then sorta-kinda in order into the 30's.

Whatever the system was, was pretty much obfuscated first by the addition of US highways in 1927, then by the 1930 re-numbering, then again by US highway changes in the mid-30s. Still, a surprising number of vestiges remain, most notably 12-14-16-[18*] (and the current 8 and 10 were later additions that fit into this pattern, whether by design or not).

*The original NY 18 was a N-S route at the west end of the state, from Buffalo south. Later it was extended up along the Niagara River, still in keeping with the system. Today, it's almost all E-W and lies north and east of its original course, but the N-S piece in Niagara County still holds true. It's actually pretty fascinating how that route has oozed continually along like a meandering river, never with any actual discontinuity from its former self!

UPDATE: I've uploaded a scan of the Automobile Blue Book map from 1925 showing NY's state routes of the time (the original system). This map was copyrighted in 1925 and to my knowledge the copyright has not been renewed, so here it is:

http://empirestateroads.com/maps/NY1925.jpg (full resolution, 11.2 Mb)
http://empirestateroads.com/maps/NY1925low.jpg (lower quality, same size, 2.7 Mb)

Quote from: route56 on November 13, 2011, 01:27:35 AM

Quote from: apeman33 on November 11, 2011, 12:01:21 PM
You can't really tell with Kansas. You can see a potential grid pattern if you go from east to west. But it's not entirely in order (K-3 west of K-7; K-14 between K-17 and K-19), some numbers aren't in said grid (K-21) and it would appear to have been created after the U.S. routes were planned because U.S. highways are in between state routes that themselves are consecutively numbered (U.S. 83 being in between K-23 and K-25).

There appears to be no sort of pattern in the east-west state routes. K-96, specifically, has nothing to do with a grid.

Actually, K-21 was in your grid... it was the original designation of US 283.

Also, remember that US 183 and US 281 were origionally designated as K-1 and K-8, respectively. Oh, and don't forget that K-99 and K-177 were originally K-11 and K-13

Then the historic grid would have went something like this (east to west):
K-7, K-3, K-6, K-11, K-13, K-15, K-17, K-14, K-8, K-19, K-1, K-21, K-23, K-25, K-27.

K-9 is an E-W route and I'm not sure where K-5 would be in the grid. I guess along the same line as K-3 as neither went border-to-border.

And I suppose one could have also included historic K-26, which would have been east of K-7.

Quote from: empirestate on November 15, 2011, 05:16:29 PM

Quote from: deanej on November 13, 2011, 11:30:13 AM

Quote from: Duke87 on November 13, 2011, 12:10:43 AM
New York, again, has no real pattern to its signed routes, but the unsigned ones have a system. In this case, all unsigned "reference routes" are three digit numbers beginning with 9 followed by a letter. The tens digit is the region number (so, for instance, route 983D is in region 8).

According to wikipedia (http://en.wikipedia.org/wiki/1930_state_highway_renumbering_(New_York)), NY's route numbers were assigned in clusters based on geographic location, though that's not followed today.

New York's original touring routes in 1924 had odd numbers for E-W routes and even numbers for N-S routes. E-W routes had a very loose progression from north to south...excluding NY 1, which by an odd mix of design and coincidence is now US 1. The rest, NY 3, 5, 7, 9, 13, 15, 17 were pretty much in order. 11 was oddball, being north of NY 5. Then you jump back a bit for 19, 21...23 is out of place...and then 25 and 27 which are still there on Long Island.

For N-S routes, you had NY 2 and 4, then from east to west you had NY 6, 8, 10, 12, 14, 16, 18...20 was oddball...then jumping back to the east for 22, 24, then sorta-kinda in order into the 30's.

Whatever the system was, was pretty much obfuscated first by the addition of US highways in 1927, then by the 1930 re-numbering, then again by US highway changes in the mid-30s. Still, a surprising number of vestiges remain, most notably 12-14-16-[18*] (and the current 8 and 10 were later additions that fit into this pattern, whether by design or not).

*The original NY 18 was a N-S route at the west end of the state, from Buffalo south. Later it was extended up along the Niagara River, still in keeping with the system. Today, it's almost all E-W and lies north and east of its original course, but the N-S piece in Niagara County still holds true. It's actually pretty fascinating how that route has oozed continually along like a meandering river, never with any actual discontinuity from its former self!

UPDATE: I've uploaded a scan of the Automobile Blue Book map from 1925 showing NY's state routes of the time (the original system). This map was copyrighted in 1925 and to my knowledge the copyright has not been renewed, so here it is:

http://empirestateroads.com/maps/NY1925.jpg (full resolution, 11.2 Mb)
http://empirestateroads.com/maps/NY1925low.jpg (lower quality, same size, 2.7 Mb)

How long did the blue book routes stay in effect?  It seems the main point of the 1930s renumbering was to incorporate those routes into the state highway system.

Quote from: deanej on November 16, 2011, 10:32:30 AM

How long did the blue book routes stay in effect?  It seems the main point of the 1930s renumbering was to incorporate those routes into the state highway system.
[/quote]

Well, Blue Books were published from 1901 until at least 1927, but their route numbers had nothing to do with state highway numberings (to my knowledge). They referred to lists of directions within the book that you could follow and are shown on this map as the numerals inside the road casing.

State highway numbers are shown in boxes next to the road symbol, as are some of the named auto trails of the day. Note that when the first blue books came out, no state had numbered highways, and their eventual adoption may have led to the quick demise of the blue book, as detailed running directions were no longer needed.

I have the 1915 Blue Book as well, and it has much more detailed road maps than the one I've scanned. Just wish I knew which box it's in...

I'm sure there is more too this state highway grid, but it appears Wisconsin assigns primary routes two digit designations, and "lesser" routes are all in the 100 series, with a few exceptions (WI-441, WI-794 for example).  It looks too like single digit routes aren't used, save US 2 and US 8.

Is this correct?  59 is a primary highway, while 159 would be a local or secondary highway?

It looks as though this might be true for county trunk highways as well.  N is primary.  NN is secondary.

Just speculation from a road atlas.

Quote from: jwolfer on November 15, 2011, 02:09:54 PM
New Jersey 5xx county routes are in a  N-S grid more or less with 502 in the north to 540 in the south.  But above 540 is random.

There seems to be some clustering 20s around Newark ( 20 21 22 23 24 28),  30s radiating out of Trenton and in Monmouth and Ocean Counties( 31 32 33 34 35 36 37). 40s radiate out of Camden.. (40( now 70) 41 42 44 45 47)

But any grid to state highways seems to have been abandoned.

NJ has two systems, neither strictly a grid.

State: 1-10 north/east of Newark, 11-20 a ring around that, 21-30 a strip of Central Jersey, 31-40 a strip of northern South Jersey, 41-50 and 51-60 further strips on the way south. But there has been a lot of renumbering in the interim.

County: Evens increase, as you say, from 502 to 540. 542 on up are all in South Jersey, with a strange leap to 560 before ending the even numbers. Odds increase from east to west, 501 to 543, and then start reflecting back across the state to 549. 551-561 are all in the southern part of the state. It gets more random after that.

Possibly the best example  of a true east-west = even number routes and  north-south =odd number routes  would be South Dakota.  Maybe  because  of it easy shape  and sparse  population.  Other  states   that have  the  same  formula  but  less obvious  would be:  Washington,  Oregon,  Florida,  Mississippi,  Indiana,  Kentucky    and Delaware.

I've always like Iowa's county highway grid system.  Seems to work great.  If a statewide system of county roads can be developed, then one for state roads should be a breeze.

East-West roads:  A## in the northern part of the state to J## in the southern part of the state.
North-South roads:  K## in the western part of the state to Z## in the eastern part of the state.
Low numbers in the western and northern parts, High numbers in the eastern and southern parts.
I, O, Q, and U are not used to avoid confusion.
Diagonal routes use L#L designations instead of L##.
Gaps are allowed, which probably wouldn't be a good idea for a state highway system.

Examples:
A16 and A18 run east-west in northern Iowa.
H34 and J40 run east-west in southern Iowa.
K12 and L26 run north-south in western Iowa.
V64 and W40 run north-south in eastern Iowa.
F8W runs diagonally in the same region as F## and W## highways.

Louisiana has a grid for the lower numbers but because the shape of the state is so strange you almost can't tell. The horizontal even numbers are seen easier.

Vertically/Odd
LA 1 - actually begins in the most northwesterly corner at the TX/AR/LA corners and heads south to the Gulf, although diagonally
LA 3 - very short north to south route just a parish east of LA 1
LA 5 - this one is an oddball and doesn't quite fit. It really goes more E-W below Shreveport
LA 7 - Now US 371, runs North South and is east of LA 3
LA 9 - North South and is east of LA 7 (US 371)
LA 11 - does not exist bc of US 11
LA 13 - runs north south but is in South LA
LA 15 - fits nicely with the northern odd highways, North to South for a large distance from the state line, to near Natchez MS and further south
LA 17 - finishes off the odds in North LA, situated in Northeast LA

*Now whats funny is the odds continue further east, but now in the "boot" of the state, east of the MS River near Baton Rouge!
LA 19 - runs North South up from baton Rouge thru Zachary
LA 21- really should be switched with LA 25 to make sense, they criss cross in Covington
LA 23 is below Lake Pontchartrain from New Orleans south to Venice
LA 25 - runs northwest of Covington rather than northeast

Horizontally/ Even  (these show up nicely on an LA map and many of them travel nearly from West to East state lines
LA 2- from Texas State line near Vivian to Lake Providence in Northeast LA
LA 4 - from US 71 south of Bossier City to St Joseph at the MS River
LA 6 - much shorter, but it flows from the TX state line at Toledo Bend to just east of Natchitoches
LA 8 - from TX state line near Leesville mostly across the central part of LA then up to Sicily Island at US 425
LA 10 - from Fort Polk near DeRidder across the entire southern boot of LA to cross MS state line past Bogalusa
LA 12 - just a short highway below LA 10 from TX state line to Ragley at US 190
LA 14 - from Lake Charles east to New Iberia

With the exception of LA 22,  LA 20-26 run east west in the boot section of LA, east of the MS River


Many of the higher groups of numbers, mostly in 10's are clustered throughout the state.
Ex: 130's in NE LA near Rayville,
120's - mostly central LA
110's - western-central LA around Kisatchie Nat'l Forest