Traveling 7 consecutive route numbers in succession

[roadman65]

If you travel NB on US 1 say from Boston, MA and then head north on it until you reach Houlton, ME you could switch on to US 2 the next number up from 1.

Then you could continue as follows:
US 2 to Lancaster, NH.
US 3 SB to Concord, NH.
US 4  WB to White River Jct, VT
US 5 SB to Hartford, CT.
US 6 WB to Danbury, CT.
Then you find US 7 to travel on.

You have a case where you can drive 7 consecutive US Routes one after the other before running out of numbers.  Too bad US 8 is in Michigan, as all you would need it to go into NY to the west of US 7 and then connect with US 9 making it complete of all single digits.

I do not think you could do that anywhere else, except maybe mixing designations like US, State, County, Secondary, etc.
I wonder if there could be more out there that could even top this to maybe 8 or higher.   

[bassoon1986]

I've got a 9 highway if you count US 66. Most likely there's a historic 66 sign though.

Start on US 59 in OK

Continue to US 60 near Afton, OK.
US 60 east to US 61 AND US 62 in Sikeston, MO
US 62 west to US 63 in Imboden, AR
US 63 south to US 64 in Marion, AR (although US 63 stops being signed here)
US 64 west to US 65 in Conway, AR
US 65 north to Historic US 66 in Springfield, MO
US 66 east to US 67 in Greater St. Louis (Kirkland?)

[bassoon1986]

If you look at historic routings there's an 8 router from US 78-85

US 78 meets US 79 in Memphis (I think...but the signage is probably spotty)
US 79 south to US 80 in Minden, LA
US 80 west (past current terminus in Dallas) to historic crossing of US 81 in Fort Worth
US 81 north to US 82 in Ringgold, TX
US 82 west to US 83 near Guthrie, TX
US 83 south to US 84 in Abilene, TX
US 84 west to US 85 near Las Vegas, NM

US 86 doesn't exist, but US 85 meets US 87 in NM as well

[english si]

You can (almost) do A70-A71-A72-A73-A74(M)-A75-A76-A77-A78-A79, but there's a couple of small gaps.

You can do A74(M)-A75-A75-A76-A77-A78-A79, which is 7.

[Alps]

Thinking in NJ only, there aren't even that many places where consecutive numbered routes touch:
[NJ 20-NJ 21-US 22] - 20 and 21 don't quite meet, separated by a short stretch of 46
[NJ 33-NJ 34-NJ 35-NJ 36]
[NJ 41-NJ 42]
[NJ 49-NJ 50]
[NJ 54-NJ 55-NJ 56]

Historically, you had a neat one with six/seven: NJ 24 (now 124 and CR 603) to Newark*, NJ 25 (now US 1/9) to New Brunswick, NJ 26 (mostly decommissioned) to downtown, NJ 27 north to Elizabeth, NJ 28 west to US 22, NJ 29 (now US 22, 202, NJ 179), NJ 30 (now NJ 31 after briefly becoming NJ 69). It meets US 206 in Trenton, but the part of 206 that was NJ 31 began in Princeton, so no match.

* Note: 24 met 1/9 downtown in the 1920s, but NJ 25 had not yet been built. 25, which is the modern routing of 1/9, never met 24, which always ended downtown or farther west. It's a close but no cigar situation.

[Duke87]

Despite Connecticut's tendency to use all low numbers for major routes, and to geographically cluster numbers, the most you get consecutively intersecting each other is three:

US 1 - CT 2 - CT 3
US 5 - US 6 - US 7
CT 79 - CT 80 - CT 81

[Kacie Jane]

I'm fairly confident there isn't a chain of more than 3 in Washington, and even for 3, I doubt there are all that many.  The only one I can come up with off the top of my head is 525/526/527.

[WNYroadgeek]

The longest chain in NY I can think of is NY 18 -> NY 19 -> US 20 -> NY 21.

[TheStranger]

The longest in CA involves an unsigned route: Route 49 -> US 50 -> unsigned Route 51.  Previously there was the sequence of Route 78 -> Route 79 -> US 80.

Not very many consecutive ones even historically:

1 and 2
4 and 5
78 and 79
88 and 89
90 and 91

(5 and 6 in the early 1960s)
(6 and 7 from 1936 to the mid-1950s)
(10 and 11 from the mid-1950s to 1981)
(14 and 15 pre-1964)
(18 and 19 pre-1964)
(28 and 29 in the late 1930s?)
(30 and 31 briefly in the early 1970s)
(98 and 99 pre-1964)

[CNGL-Leudimin]

Despite here in Spain almost all routes have at least 3 digits (Expressways normally have 2), I got some route chains:
CM-41 => A-42, which turns into CM-42 => A-43. Too bad AP-41 doesn't interchange with A-42, then we would have had CM-40, which ends at A-40 => AP-41 => A-42, which turns into CM-42 => A-43.
A-30 => A-31 => A-32.
A-130 => A-131 => through Huesca (usually no numbers are signed inside cities) to A-132. If A-129 had been built as planned, then it would have intersected A-130, making it A-129 => A-130 => A-131 (closing a loop as it would have multiplexed with A-129 in Sariñena) => A-132.
If NA-8701 was part of NA-125, then we would have A-124 => A-125, which turns into NA-125 => NA-126, which turns into A-126 => A-127 (Including a brief duplex with A-125 in Ejea, thus completing a loop), which turns into NA-127. Incidentally, A-123 ends at N-330 a mile North (East) of where A-124 starts, and A-1201, which starts at A-127, turns into NA-128.
And we would have the chain with the highest numbers with A-1209 => A-1210 (unsigned for the first few miles) => A-1211... if the first two ended at the same point on N-330 (They end less than a mile apart).

[ftballfan]

In Michigan, there aren't that many of two and I can't think of any of three or more at any time:
M-24 and M-25 at Unionville
M-32 and M-33 at Atlanta (includes a multiplex)
M-46 and M-47 at Saginaw (used to include a multiplex)

There used to be US-24 and US-25 in Monroe County and US-31 and M-32 at Charlevoix

[CNGL-Leudimin]

I found a couple more:
A-222 => A-223 => A-224.
And A-1408 and A-1410 ends at Castelserás are separated by a few yards of... yes, A-1409!

[bassoon1986]

For just Louisiana the only 3 router off the top of my head is LA 1, LA 2, LA 3. Im sure there are others.


Actually just found one more: 742-743-744 near Opelousas.

[Beeper1]

In Rhode Island there's:

US 1 -> RI 2 -> RI 3
RI 115 -> RI 116 -> RI 117 

[Alps]

DC: How about, how many state-named roads are linked in order of admission to the Union? I have them all mapped out at work but not easily discernable which is which.

[roadfro]

The only successive possibilities I could find in Nevada that involve three or more routes:

• SR 397 -> SR 398 -> SR 399 -- in Lovelock
  
• Former SR 428 -> Former SR 429 -> Former SR 430 -> SR 431 -- in Washoe Valley & South Reno
  
• SR 445 -> SR 446 -> SR 447 -- near Pyramid Lake
  
  With Nevada's clustering system, you'd think this would be easier. There are multiple locations where if NDOT had selected route numbers in different orders (or actually maintained as state highways some of the old federal/state aid routes), there could've been several drivable successions.

[vtk]

I'm sure there's enough insane proposals in Fictional Highways to make possible a chain of Interstates 64—101...

[Rover_0]

Drive on US-89/91 SB to UT-90 WB, U-turn to go EB on UT-90, head on US-89/91 NB. Oh wait, that's only 3 routes, but that's about as good as you can get in Utah without leaving the state.

[NWI_Irish96]

I think 7 is the best you can get in Indiana with US35-US36-IN37-IN38-IN39-US40-US41

[Duke87]

DC: How about, how many state-named roads are linked in order of admission to the Union? I have them all mapped out at work but not easily discernable which is which.

Depends on whether we insist they directly intersect or accept it if they just logically cross. For instance, Massachusetts and Maryland Avenues "cross" at Stanton park but they both end at one corner and begin again at the opposite corner, and hence to not directly intersect. Similarly, going between Connecticut and Massachusetts requires a short trip on Dupont Circle.

With the strictest interpretation, the only adjacent two that intersect are NV-NE.

Allow a looser interpretation as mentioned above and you also have:
CT-MA-MD
NH-VA
RI-VT
KY-TN

And that's it.