State Highway grids

[OCGuy81]

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?

[3467]

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

[realjd]

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).

[corco]

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.

[OCGuy81]

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?

[J N Winkler]

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.

[vtk]

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.

[J N Winkler]

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.

[apeman33]

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.

[dfilpus]

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.

[tdindy88]

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

[Quillz]

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.

[NE2]

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?

[Takumi]

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.

[Quillz]

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.

[corco]

And 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.

[TheStranger]

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.

[Dr Frankenstein]

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.

[Eth]

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).

[formulanone]

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.

[roadman65]

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.

[NE2]

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.)

[dave19]

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.

[luokou]

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)

[xonhulu]

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)

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!

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.

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)

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

138, 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?

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)

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.