States that Disallow Route Number Duplication

[Henry]

Having lived in California, I've learned from studying its routes that it does not allow any two of its routes to share the same number, and has done so since 1964, with the exception of extended routes (I-110/CA 110 and I-238/CA 238) and future routes (CA 905 to become I-905 within a few years). Which is why US 40 and US 80 no longer exist there, with the coming of I-40 and I-80, and US 70 is also gone because CA 70 exists further north.

What other states also prohibit route numbers from being duplicated?

[NE2]

Prohibit is too strong a word. Caltrans could decide to duplicate numbers if they signed a legislative route with a different sign route number (like they sign SR 61 along SR 112 and SR 260, but without any 'correct' section).

You also have cause and effect somewhat wrong. US 40, US 70, and US 80 no longer enter California because Interstates replaced them, not because their numbers were taken. (SR 70 was in fact a new number in the 1964 renumbering, replacing US 40 Alternate.)

[corco]

Pretty much every state that codifies its state highways practically disallows route duplicates, except in the situation NE2 alluded to.

So that tacks on Washington and Utah, among others. Then Nebraska and Colorado don't allow duplication either (although Nebraska has awkward gaps in highways that are technically the same highway and Colorado has instances of US-36/SH-36, US-40/SH-40, etc, but they all follow the same functional corridor and it gets fairly complicated)

Idaho doesn't have any duplicates, but I'm not sure if that's policy or just the way the dog shook.

Prohibit is too strong a word. Caltrans could decide to duplicate numbers if they signed a legislative route with a different sign route number (like they sign SR 61 along SR 112 and SR 260, but without any 'correct' section).

I would say that there is prior evidence that California prohibits route duplication. We know as a matter of fact that when I-238 was established, the AASHTO recommended I-180 and California said "no, because we have a State Route 180"

[Revive 755]

Missouri used to, though the more recent interstate additions seem to have broken Missouri's will to avoid duplication.  There's now both a MO 64 and I-64, MO 72 and I-72, and there will soon be both MO 49 and I-49.

[NE2]

I would say that there is prior evidence that California prohibits route duplication. We know as a matter of fact that when I-238 was established, the AASHTO recommended I-180 and California said "no, because we have a State Route 180"

Full quote: "We already have a state route 180 in our Fresno area, and this route is separated from I-580 in Castro Valley by about 100 miles." If existing SR 180 were in San Diego they might have been willing.

[corco]

Quote from: corco on Today at 03:00:31 PM
I would say that there is prior evidence that California prohibits route duplication. We know as a matter of fact that when I-238 was established, the AASHTO recommended I-180 and California said "no, because we have a State Route 180"
Full quote: "We already have a state route 180 in our Fresno area, and this route is separated from I-580 in Castro Valley by about 100 miles." If existing SR 180 were in San Diego they might have been willing.

I read that as meaning that the route is too far separated from the proposed 180 routing to merit a signed concurrency connecting the two routes, so they wouldn't do it. If the route were closer, they would have considered it.

[NE2]

Perhaps.

But California did continue to sign US 40 and US 80 after the renumbering until the Interstates that replaced them were sufficiently complete. They just didn't use the numbers internally.

[Beeper1]

Connecticut, Massachusetts, and RI all do not allow duplicate numbers.  There have been cases of multiple states having to renumbr a route because another state had to change a route number to avoid duplication (especially when the interstates were being built) and the neighboring state the route crossed into had to change their end. 

Mass has he only exception in that there is I-295 and a MA 295.  The reason these are allowed is they are both less than 5 miles long and are on opposite ends of the state. They both continue routes from neighboring states.  Actually, MA 295 used to just be signed as "To NY 295" at its Mass end for years.  Only recently was it signed as MA 295 in its own right. Always been a state maintained road as far as I know.

[agentsteel53]

Full quote: "We already have a state route 180 in our Fresno area, and this route is separated from I-580 in Castro Valley by about 100 miles." If existing SR 180 were in San Diego they might have been willing.

I wonder why CA didn't renumber 180.  they have historically not been averse to it.  in fact, 128 was renumbered in 1951 from 28 to make room for a CA-28 that connects to NV-28.  (interestingly, when NV renumbered in the 70s, they kept 28 and 88, which continued California numbers, as the only two in the system with fewer than three digits)

[agentsteel53]

Hawaii does not have duplicates because 10 is their lowest-numbered state highway, intentionally. 

though they are apparently in the process of designating an old alignment of 200 on the Big Island as county route 201.  Hawaii county-maintained routes have the same raindrop shield as the state highways, so it is left as an exercise to the reader if this coincides with Oahu's interstate H201.

[oscar]

Hawaii doesn't strictly prohibit duplication, but the system for assigning route numbers (single-digit route numbers reserved for Interstates and interisland ferries, each county has its own reserved block of two- through four-digit state and county routes) makes duplication unlikely.  Some related state and county routes share the same number, such as state 340 on Maui turning into county 340, or state 31 which once was connected to county 31.  This is because Hawaii at statehood had one route number system lumping together state and county routes, which only later was broken into two separate systems but most of the numbers stayed the same. 

Technically, Interstate H-201 on Oahu could be considered to duplicate secret state route 201 on the Big Island (concurrent with state 200 west of mile 42, which in a few years is to be bypassed by a new alignment and turned over to the county).  But not really, since Hawaii DOT considers the "H-" prefix to be part of the Interstate's route number.

[myosh_tino]

I would say that there is prior evidence that California prohibits route duplication. We know as a matter of fact that when I-238 was established, the AASHTO recommended I-180 and California said "no, because we have a State Route 180"

Full quote: "We already have a state route 180 in our Fresno area, and this route is separated from I-580 in Castro Valley by about 100 miles." If existing SR 180 were in San Diego they might have been willing.

Hmmm... so your saying if CA-180 were in San Diego, then Caltrans would have considered using I-180 in the S.F. Bay Area?  I don't know about that.  It was my understanding that route duplication is simply not allowed.

To the original poster, 110 and 238 are extensions of existing highways.  CA-110 is an extension of I-110 onto the Arroyo Seco Parkway which is not up to Interstate standards (and cannot be upgraded due to it's historical nature).  I-238 is an extension of CA-238/Mission Blvd.  CA-905 will probably become I-905 once the freeway from I-805 to the Mexican border is completed (it's currently a 4-6 lane expressway).  I also believe CA-210 will become I-210 once California gets around to asking AASHTO to include the entire route in the interstate system.

[Quillz]

Yes, I believe California simply doesn't allow route duplication, plain and simple. Even if they wanted to build an Interstate 161 along the Mexican border, it wouldn't be allowed due to the presence of CA-161 at the northern border, some 700+ miles away.

[Michael in Philly]

I would say that there is prior evidence that California prohibits route duplication. We know as a matter of fact that when I-238 was established, the AASHTO recommended I-180 and California said "no, because we have a State Route 180"

Full quote: "We already have a state route 180 in our Fresno area, and this route is separated from I-580 in Castro Valley by about 100 miles." If existing SR 180 were in San Diego they might have been willing.

And they already have a Cal. 238 right around the corner!
There is no excuse for I-238.  None.

[Quillz]

I-238 briefly made sense during the 1980s when every possible x80 auxiliary was used up, but since 1991, I-480 has been available. And that should be used. It even makes perfect sense, as even-numbered 3di have a tendency to start and end at Interstates and serve as loops or bypasses.

Of course, there is always the proposition of replacing I-238 with I-980 and returning CA-24 to its former length. But I-238 simply should not exist anymore.

[Roadgeek Adam]

Pennsylvania is a main issue, and its due to their own stupidity if you ask me. If you have SR 283 attached to I-283, then don't designate PA 283 as PA 283, designate PA 283 as PA 300, as its SR 300. Same for PA 380/SR 400. If we're so worried on confusion, then SIGN the change! PA 222 is just dumb in my opinion.

New Jersey gets credit from me for the 1953 renumbering working on eliminated duplexed designations. NJ 77 in south jersey was NJ 46 and was renumbered to avoid US 46 and NJ 46. NJ 76 was renumbered to 81 in proposals to can the 76 repeation.

New York is going backwards. They did a great job with no duplication. Now NY 695, NY 86, NY 88, NY 295 all duplicate. Its really silly. NY 87 was renumbered to 812, a part of 88 went to be 488, NY 84 became 284, NY 78 is a borderline issue, etc. Its just getting dopey.

[RoadWarrior56]

Indiana does not allow route number duplication between US numbered highways and State numbered highways, although there can be and are duplications between Interstates and state numbered highways (the most obvious being SR 64 intersecting I-64).

When the US Highway system came into existence, the Indiana state route numbers were changed in order to fit the US Highways into a common grid with the state highways.  When I worked in Indianapolis while in college back in the 1970's, I had visited the State Library and found some very old road maps.  There was one from the early 30's that had the current numbering system, but US 35 had not yet been signed in Indiana.

What is now SR 135, which starts on the Ohio River south of Corydon and continues north to Indianapolis, was numbered on that map as SR 35.  SR 35 actually fits the Indiana grid almost perfectly, with SR 37 to the west and US 31 to the east.  Obviously, when US 35 entered the state, SR 35 was renumbered as SR 135, hence the violation the grid, but the prevention of a route duplication.

[Duke87]

Has New York ever had a US/state duplication?

I ask because while reference markers clearly put "I" as a suffix on interstates, no special suffix appears for US routes. So, for instance, reference markers for US 9 and a theoretical NY 9 would both carry just the number "9" and thus be ambiguous from each other.

[Hot Rod Hootenanny]

Ohio has a long history of not allowing number duplication.
Renumbering in 1926 for US highways http://pages.prodigy.net/john.simpson/highways/rr1926.html
Renumbering in 1962 for Interstate http://pages.prodigy.net/john.simpson/highways/rr1962.html

[cu2010]

Has New York ever had a US/state duplication?

I ask because while reference markers clearly put "I" as a suffix on interstates, no special suffix appears for US routes. So, for instance, reference markers for US 9 and a theoretical NY 9 would both carry just the number "9" and thus be ambiguous from each other.

There is both US2 and NY2 (though US2 exists for less than a mile before going into Vermont, and NY2 is nowhere near US2)...the reference markers for US2 say "2U".

There is also US15 and NY15, though in that case, NY15 was formerly US15 (and used to extend from the current northern terminus of US15 until NYSDOT removed signage for NY15 along I-86/NY17 and I-390). Like US2, US15 is regarded as "15U".

US220 also exists in NY conflicting with NY220, however, US220 in NY is less than a tenth of a mile long, and is locally maintained, thus having no inventory number or reference markers.

[Michael]

There is also US15 and NY15, though in that case, NY15 was formerly US15 (and used to extend from the current northern terminus of US15 until NYSDOT removed signage for NY15 along I-86/NY17 and I-390). Like US2, US15 is regarded as "15U".

NYSDOT Traffic Data Reports refer to it as 15U, but when I was on US 15 back in 2008, I saw reference markers that said 99I.

Adam, you missed I-90 and NY 90.  They even cross each other in Montezuma!

On a side note, I like how NY signs extensions of Interstates as NY routes.

[roadfro]

Nevada does not duplicate numbers between systems, at least since the 1976 renumbering of state highways. Given the numbers that were used, NDOT anticipated back in 1976 (or may have already been planning to) eventually building I-515 in Las Vegas, even though the 510-530 numbers were being assigned to roads around Carson City--I-515 was finally signed in 1994-95.

Prior to the 1976 renumbering, state route alignments were somewhat codified in state law. These were created sequentially and without regard for the U.S. routes. So at that time, we had both US highways and state highways duplicating routes 6, 40, 50, 91 & 93--none of the state route numbers intersected or were located in any close proximity to the US counterpart.

[JREwing78]

Wisconsin, with one exception (I-39), does not use route number duplicates. And in that case, they could change the existing state highway to 139 or 239 without issue, but apparently determined nobody would confuse it for the interstate.

[vdeane]

Adam, you missed I-90 and NY 90.  They even cross each other in Montezuma!

Not to mention NY 81/I-81, NY 190/I-190, and NY 290/I-290!  NY 87's conversion to NY 812 is the exception that proves the rule of NY not caring.

[Roadgeek Adam]

Adam, you missed I-90 and NY 90.  They even cross each other in Montezuma!

Not to mention NY 81/I-81, NY 190/I-190, and NY 290/I-290!  NY 87's conversion to NY 812 is the exception that proves the rule of NY not caring.

Must we seriously care how much I missed?

I just came up with the three that came in my head, don't need to add every single one.