In western NC, US 74 was realigned to an expressway, leaving behind a 60-mile long US 74A. This is by far the longest signed alternate route I have ever seen.
Not as long as your example, but the pieces of US 220 left behind with the I-99 conversion are long. Business US 220 on either side of Altoona (pop 45k) is 37 miles long. Alternate US 220 left from the move over to State College is 19 miles long.
Nexus 6P
Look west for long alternate routes. Like Alt US 89 in AZ and UT, about 90 miles long. Alt US 93 in Nevada is about 120 miles, though about half is on I-80 to connect the route back to US 93.
US 20's alternate, US 20A, is over 80 miles long in western New York.
The US-1A in Maine that runs through Bangor and down to Ellsworth is around 54 miles long.
How about MA 2A?
1A and 3A are unsigned during their overlaps with US 1 and US/MA 3, but if the unsigned parts were included, they would also be long.
Well, if letter-suffixed routes count for this, then New York has some pretty long ones. NY 9A and NY 25A come to mind particularly.
From the TravelMapping database, here are all bannered US highways (Alt, Truck, Bypass, etc) with length at least 20 miles.
+-------+--------+--------------------+---------+
| route | banner | groupName | mileage |
+-------+--------+--------------------+---------+
| US90 | Alt | Hallettsville, TX | 181.209 |
| US41 | Alt | Nashville, TN | 175.046 |
| US17 | Alt | Summerville, SC | 124.284 |
| US93 | Alt | Wendover, NV | 118.617 |
| US95 | Alt | Yerington, NV | 106.962 |
| US93 | Trk | Laughlin, NV | 103.237 |
| US14 | Alt | Powell, WY | 96.6977 |
| US27 | Alt | Perry, FL | 94.8721 |
| US27 | Alt | Newnan, GA | 94.5854 |
| US77 | Alt | Cuero, TX | 91.3049 |
| US89 | Alt | Fredonia, AZ | 90.0674 |
| US58 | Alt | Abingdon, VA | 84.5404 |
| US78 | Alt | Jasper, AL | 84.2952 |
| US20 | Alt | Geneseo, NY | 83.7864 |
| US64 | Trk | Henderson, NC | 78.6879 |
| US31 | Alt | Nashville, TN | 77.7624 |
| US72 | Alt | Decatur, AL | 69.2461 |
| US264 | Alt | Wilson, NC | 64.5371 |
| US45 | Alt | West Point, MS | 64.4356 |
| US50 | Alt | Pollock Pines, CA | 63.0346 |
| US70 | Alt | Gibson, TN | 62.0524 |
| US74 | Alt | Asheville, NC | 53.8992 |
| US20 | Alt | Maumee, OH | 52.9627 |
| US1 | Alt | Bangor, ME | 50.4554 |
| US41 | Alt | Dixon, KY | 50.3691 |
| US1 | Alt | Fort Fairfield, ME | 50.0701 |
| US129 | Alt | Macon, GA | 49.0726 |
| US83 | Bus | McAllen, TX | 46.6159 |
| US2 | Alt | Houlton, ME | 43.4096 |
| US97 | Alt | Entiat, WA | 39.8004 |
| US14 | Alt | Deadwood, SD | 38.628 |
| US321 | Bus | Conover, NC | 37.9654 |
| US220 | Bus | Altoona, PA | 37.7905 |
| US19 | Alt | St. Petersburg, FL | 37.7102 |
| US287 | Bus | Fort Worth, TX | 36.2262 |
| US75 | Alt | Tulsa, OK | 33.9563 |
| US19 | Trk | Waynesville, NC | 33.1961 |
| US412 | Alt | Locust Grove, OK | 33.1776 |
| US50 | Alt | Fernley, NV | 32.6956 |
| US71 | Bus | Fayetteville, AR | 32.3559 |
| US40 | Alt | Cumberland, MD | 30.972 |
| US64 | Alt | Bethel, NC | 30.6956 |
| US24 | Bus | Peru, IN | 30.3403 |
| US16 | Alt | Custer, SD | 28.1716 |
| US209 | Trk | Brodheadsville, PA | 28.1006 |
| US220 | Alt | Candor, NC | 27.3461 |
| US201 | Alt | Skowhegan, ME | 26.1564 |
| US221 | Alt | Forest City, NC | 25.3705 |
| US20 | Bus | South Bend, IN | 24.74 |
| US70 | Bus | Smithfield, NC | 23.9041 |
| US17 | Bus | Myrtle Beach, SC | 23.0378 |
| US40 | Alt | Hagerstown, MD | 22.6349 |
| US220 | Alt | Milesburg, PA | 22.2194 |
| US20 | Bus | Rockford, IL | 22.0608 |
| US29 | Bus | Lynchburg, VA | 21.8223 |
| US74 | Bus | Forest City, NC | 21.3149 |
| US220 | Bus | Asheboro, NC | 20.36 |
| US69 | Alt | Baxter Springs, KS | 20.3555 |
| US395 | Alt | Washoe City, NV | 20.0554 |
+-------+--------+--------------------+---------+
59 rows in set (0.04 sec)
Quote from: dgolub on May 29, 2017, 09:28:08 AM
Well, if letter-suffixed routes count for this, then New York has some pretty long ones. NY 9A and NY 25A come to mind particularly.
And related to NY, VT's 22A is almost 45 miles long. Longest A route in CT is CT 14A at about 10 1/2 miles. US 6A in CT used to be about 40-45 miles long from Woodbury to Willimantic. FTR, MA 1A is officially about 95 miles long.
In terms of Interstate business routes, North Carolina regards both pieces of its Green I-85 as a single route that totals around 43.5 miles. That seems quite long for a Green Interstate (I have not looked to see if another is longer).
US Route 20A in northwest Ohio is about 53 miles long.
https://goo.gl/maps/ahD2wZkSgGK2
Business Route 20 in north central Illinois is about 22 miles long.
https://goo.gl/maps/TQZ6WtYku4w
Business I-70 in Denver is about 24 miles long.
https://goo.gl/maps/1GDUyCMcuGt
Here are the Interstate business loops/spurs in the TM database that extend more than 20 miles. It appears we consider that I-85 BL that 1995hoo mentioned as separate pieces.
+-------+--------+---------------+---------+
| route | banner | groupName | mileage |
+-------+--------+---------------+---------+
| I-20 | BL | Midland, TX | 31.1842 |
| I-85 | BL | Lexington, NC | 30.3644 |
| I-70 | BL | Denver, CO | 27.4552 |
| I-76 | BS | Atwoord, CO | 26.4601 |
| I-40 | BL | Amarillo, TX | 24.6999 |
| I-49 | BL | Joplin, MO | 22.6758 |
| I-5 | BL | Orland, CA | 20.9681 |
+-------+--------+---------------+---------+
7 rows in set (0.12 sec)
It may not be the longest per se, but I-80 Business in Sacramento is a 15-mile partial beltway around the city. It's a major freeway and long, making it somewhat anomalous. It should be a 3di (indeed, it is unsigned I-305 in addition to being I-80 business).
Quote from: Jim on May 29, 2017, 11:01:33 AM
Here are the Interstate business loops/spurs in the TM database that extend more than 20 miles. It appears we consider that I-85 BL that 1995hoo mentioned as separate pieces.
....
I think your approach is the correct one. I noted it simply because the State of North Carolina evidently views it differently.
U.S. 40 in Maryland has three bannered Alternate routes. Two are true ALT routes, one, in Baltimore City, is a truck route.
Between Keyser's Ridge and Cumberland, U.S. 40 follows I-68, but there's an Alternate U.S. 40 (https://www.google.com/maps/dir/39.657407,-78.7489985/39.694625,-79.247547/@39.6711699,-79.2791597,10z/data=!3m1!4b1!4m29!4m28!1m25!3m4!1m2!1d-78.7885251!2d39.6695299!3s0x89ca8e894b42fdeb:0xe77e3c42c7c465b1!3m4!1m2!1d-78.9061874!2d39.6538907!3s0x89ca911fd7f336ad:0xb23e37b22b6fd738!3m4!1m2!1d-78.9467243!2d39.6765518!3s0x89ca96c0d3b5b639:0x3c49cc515025afed!3m4!1m2!1d-79.0281285!2d39.6870118!3s0x89cabdf32603bd59:0x743593df41458ce!3m4!1m2!1d-79.116293!2d39.6953798!3s0x89cabbf3580fcf91:0xffb8ab78ccbff75c!1m0!3e0) that takes drivers past Penn Alps, Finzel, Frostburg, LaVale, The Narrows and downtown Cumberland. This is generally the easternmost part of the National Road or National Pike, about 31 miles.
Then U.S. 40 has a bannered and well-signed alternate (https://www.google.com/maps/dir/39.4197029,-77.4615837/39.6389896,-77.7221868/@39.5289667,-77.7323123,11z/data=!3m1!4b1!4m14!4m13!1m10!3m4!1m2!1d-77.5475147!2d39.4438812!3s0x89c9dd6e29bf2cb3:0x1f3b838813a3a451!3m4!1m2!1d-77.6587045!2d39.5177363!3s0x89c9ef320b9bfe71:0x95dc029e76c35e49!1m0!3e0) that runs from the downtown area of Hagerstown to the west edge of Frederick, passing through Funkstown (but no direct access to I-70), Boonsboro, Middletown and Braddock Heights, covering about 23 miles. This is also the original U.S. 40 routing - the current route of U.S. 40 (https://www.google.com/maps/dir/Hagerstown/39.4198406,-77.4625471/@39.4822595,-77.8304242,10z/data=!4m9!4m8!1m5!1m1!1s0x89c9ed151481dfdd:0x65f2620826df7239!2m2!1d-77.7199932!2d39.6417629!1m0!3e0) passes through mostly very rural areas (by Maryland standards).
The two above routes are more interesting from a cultural perspective than the parallel freeways.
Baltimore City has the (not always well-signed) TRUCK U.S. 40 (https://www.google.com/maps/dir/39.2940691,-76.6720323/39.3011137,-76.5500357/@39.3074687,-76.6826027,12z/data=!3m1!4b1!4m19!4m18!1m15!3m4!1m2!1d-76.6279558!2d39.3105856!3s0x89c804c7ed9de1d1:0xd34054298ae69020!3m4!1m2!1d-76.5823943!2d39.3140319!3s0x89c8044548161d65:0xd47ab90b25bf6be9!3m4!1m2!1d-76.5716883!2d39.3202271!3s0x89c8043589214bfb:0x23e203b4c04d2b72!1m0!3e0) that's about 9 miles end-to-end.
Quote from: dgolub on May 29, 2017, 09:28:08 AM
Well, if letter-suffixed routes count for this, then New York has some pretty long ones. NY 9A and NY 25A come to mind particularly.
Then we have NY 9N, which is just over
143 miles (longest in the state).
U.S. 89 has a 92 alternate route from Kanab, UT to Bitter Springs, AZ.
US 27 Alternate in FL between Williston and Perry is 96 miles long.