I just saw a post talking about an alternate route that most people don't know about, so I thought I'd start a thread dedicated to these routes. Here are a few of mine:
Town of Throop, NY to Port Byron, NY
Common (http://maps.google.com/maps?f=d&source=s_d&saddr=County+Route+10B%2FTurnpike+Rd&daddr=Rochester+St&geocode=FWa3jwIdgCRv-w%3BFSCskAIdrLJu-w&hl=en&mra=mi&mrsp=1,0&sz=19&sll=43.035621,-76.63124&sspn=0.001468,0.003484&ie=UTF8&ll=43.007534,-76.607151&spn=0.094022,0.222988&z=13)
Alternate (http://maps.google.com/maps?f=d&source=s_d&saddr=County+Route+10B%2FTurnpike+Rd&daddr=42.9981602,-76.6178766+to:Rochester+St&geocode=FWa3jwIdgCRv-w%3BFZAZkAIdbOdu-ym38rwsNK3QiTHWvqQJMflpeQ%3BFSCskAIdrLJu-w&hl=en&mra=mi&mrsp=1,0&sz=19&sll=43.035621,-76.63124&sspn=0.001468,0.003484&ie=UTF8&ll=43.007534,-76.607151&spn=0.094022,0.222988&z=13&via=1)
Carousel Center to Fairmont Fair, Syracuse, NY
Common (http://maps.google.com/maps?f=d&source=s_d&saddr=Carousel+Center&daddr=County+Rd+98%2FW+Genesee+St&geocode=FXcnkQId0bh1-w%3BFRvdkAIdOch0-w&hl=en&mra=ls&sll=43.052646,-76.223445&sspn=0.375808,0.891953&ie=UTF8&z=14)
Alternate (http://maps.google.com/maps?f=d&source=s_d&saddr=Carousel+Center&daddr=43.0564,-76.187045+to:County+Rd+98%2FW+Genesee+St&hl=en&geocode=FXcnkQId0bh1-w%3BFRD9kAIdW3p1-ymb0mbVZPHZiTEBUvog9UeFSw%3BFRvdkAIdOch0-w&mra=ls&sll=43.06456,-76.2038&sspn=0.046967,0.111494&ie=UTF8&z=14&via=1)
NY 34/13 Interchange to Sciencenter, Ithaca, NY
Common (http://maps.google.com/maps?f=d&source=s_d&saddr=Gibbs+Dr%2FJames+L+Gibbs+Dr&daddr=1st+St&geocode=FdjyhwIdtLdw-w%3BFTG7hwIdlaBw-w&hl=en&mra=ls&sll=42.449697,-76.495314&sspn=0.011859,0.027874&ie=UTF8&ll=42.456046,-76.502867&spn=0.023715,0.055747&z=15)
Alternate (http://maps.google.com/maps?f=d&source=s_d&saddr=Gibbs+Dr%2FJames+L+Gibbs+Dr&daddr=42.4483487,-76.5001249+to:1st+St&geocode=FdjyhwIdtLdw-w%3BFdy1hwIdZLNw-ykl1cajgYHQiTEslTxc7hkWOg%3BFTG7hwIdlaBw-w&hl=en&mra=ls&sll=42.449697,-76.495314&sspn=0.011859,0.027874&ie=UTF8&ll=42.456046,-76.502867&spn=0.023715,0.055747&z=15&via=1)
Auburn NY to Selinsgrove, PA (a few options)
Common (I-81, used the first time I went) (http://maps.google.com/maps?f=d&source=s_d&saddr=South+St&daddr=41.59867,-75.64917+to:Susquehanna+Trail&geocode=FYbojgId_rRv-w%3BFc6-egIdbq99-ykN7Z-yXNTEiTFhAdQlQ1ImRw%3BFfoWbwId2JNr-w&hl=en&mra=ls&sll=40.761821,-76.690063&sspn=1.558141,3.56781&ie=UTF8&z=8&via=1)
I-81 via Cortland (http://maps.google.com/maps?f=d&source=s_d&saddr=South+St&daddr=Old+Stage+Rd+to:Susquehanna+Trail&geocode=FYbojgId_rRv-w%3BFVoFigId_FBz-w%3BFfoWbwId2JNr-w&hl=en&mra=ls&via=1&sll=42.629917,-76.094055&sspn=0.756775,1.783905&ie=UTF8&z=8)
Alternate (mostly US 15, my usual route) (http://maps.google.com/maps?f=d&source=s_d&saddr=South+St&daddr=I-86+W+to:Susquehanna+Trail&geocode=FYbojgId_rRv-w%3BFWgRgwIdER9q-w%3BFfoWbwId2JNr-w&hl=en&mra=ls&via=1&sll=41.816361,-76.442871&sspn=3.066217,7.13562&ie=UTF8&ll=41.898188,-76.860352&spn=3.062298,7.13562&z=8)
Google suggested other routes, but I've never tried them. The NY 414 suggestion seems out of the way to me.
Laramie WY to Front Range/I-25 Corridor Colorado (http://maps.google.com/maps?f=d&source=s_d&saddr=laramie+wy&daddr=US-287+S+to:40.610043,-105.014362+to:I-25+S&hl=en&geocode=FYdcdgIdw860-Sl5m9qO94RohzGT5cSh98GJjg%3BFeiybAId9hi7-Q%3B%3BFSCwZAId1CO--Q&mra=dme&mrcr=0&mrsp=2&sz=13&via=1,2&sll=40.603396,-105.018997&sspn=0.056433,0.169086&ie=UTF8&ll=40.598313,-105.049381&spn=0.056438,0.169086&z=13)
(I-80 to I-25 or 287 S to SH-14 would be the common routes- this mostly alleviates the reason why some folks don't take the 287 to 14 route by cutting out the bulk of FoCo traffic, which can slow it down to taking as long as 80 to 25 (when traffic is light, 287 to 14 saves 12 minutes or so))
Santa Maria to Santa Barbara
Common (http://maps.google.com/maps?f=d&source=s_d&saddr=Santa+Maria,+CA&daddr=34.470335,-120.233002+to:Santa+Barbara,+CA&hl=en&geocode=FUpXFQId-UvS-CkJxlQMqg_sgDGONFqKZVL9Cw%3B%3BFV44DQId8ozd-CnVgy1vxxTpgDFIdrrXZDrRyA&mra=dpe&mrcr=0&mrsp=1&sz=10&via=1&sll=34.68464,-120.066995&sspn=0.67867,1.108246&ie=UTF8&z=10)
Shorter Alternate (http://maps.google.com/maps?f=d&source=s_d&saddr=Santa+Maria,+CA&daddr=Santa+Barbara,+CA&hl=en&geocode=FUpXFQId-UvS-CkJxlQMqg_sgDGONFqKZVL9Cw%3BFV44DQId8ozd-CnVgy1vxxTpgDFIdrrXZDrRyA&mra=mr&mrcr=0&sll=34.68464,-120.066995&sspn=0.67867,1.108246&ie=UTF8&z=10)
For I-77 (traveling southbound) in in Akron:
SR 21 to I-76/U.S. 224 EB
Stay on 224 EB to I-77
Here's a good alternative to I 84 in southern Idaho: Take exit 111 to US 30 , a parelell route down to the Snake River and be totally blown away by the Thousand Springs, underground rivers forming thousand of waterfalls on lava cliffs into the river below. You then follow 30 into Twin Falls. It is well worth the detour from a typical interstate where everyone is going 85 or faster!
fall
I-70 - MD/WV/PA
Common (http://maps.google.com/maps?f=d&source=s_d&saddr=I-70+W&daddr=40.044832,-80.64703&geocode=FfI5WQIdLkJi-w%3BFSAJYwIdimwx-w&hl=en&mra=mi&mrsp=0&sz=15&sll=39.401051,-77.457776&sspn=0.023114,0.036607&ie=UTF8&ll=39.762103,-79.035645&spn=2.942985,4.685669&z=8%5Burl=http://Common)
Toll & PA Turnpike free alternative (http://maps.google.com/maps?f=d&source=s_d&saddr=I-70+W&daddr=39.59299,-79.963989+to:40.044832,-80.64703&geocode=FfI5WQIdLkJi-w%3B%3BFSAJYwIdimwx-w&hl=en&mra=dpe&mrcr=0&mrsp=1&sz=8&via=1&sll=39.81304,-79.05245&sspn=2.94082,4.685669&ie=UTF8&ll=39.96028,-79.260864&spn=2.934501,4.685669&z=8%5Burl=http://Toll%20&%20PA%20Turnpike%20free%20alternative)
Well, here's a couple up here in Utah's (and Idaho's) Cache Valley:
--UT-252 from US-89/91, back to US-91, north of Logan. While you go as slow as 30 MPH in one spot, you avoid the pain in the neck that is downtown Logan. The people at UDOT I converse with say that the purpose of establishing this highway was that it could be a truck route, serving the industrial section in western Logan and avoiding downtown Logan.
--UT-23/Westside Hwy. Franklin County Route D1 (was ID-23), from US-89/91 in Wellsville, UT, through Mendon, UT, Weston, ID, and Clifton, ID, ending at US-91 near Swanlake, ID. Honestly, this could be a legitimate US alternate route.
Main--http://maps.google.com/maps?f=d&source=s_d&saddr=Wellsville,+UT&daddr=Swanlake,+ID&hl=en&geocode=FY9aewIddgZU-SlRIT3OO35ThzEDDwUd3FXv-Q%3BFRClhQId-fRS-SlVRmge2ANVhzEb3ACzb96K3A&mra=ls&sll=41.672912,-111.796875&sspn=11.91094,19.709473&ie=UTF8&z=10 (http://maps.google.com/maps?f=d&source=s_d&saddr=Wellsville,+UT&daddr=Swanlake,+ID&hl=en&geocode=FY9aewIddgZU-SlRIT3OO35ThzEDDwUd3FXv-Q%3BFRClhQId-fRS-SlVRmge2ANVhzEb3ACzb96K3A&mra=ls&sll=41.672912,-111.796875&sspn=11.91094,19.709473&ie=UTF8&z=10)
Alternate--http://maps.google.com/maps?f=d&source=s_d&saddr=Wellsville,+UT&daddr=42.002366,-111.958923+to:Swanlake,+ID&hl=en&geocode=FY9aewIddgZU-SlRIT3OO35ThzEDDwUd3FXv-Q%3B%3BFRClhQId-fRS-SlVRmge2ANVhzEb3ACzb96K3A&mra=dpe&mrcr=0&mrsp=1&sz=10&via=1&sll=41.975925,-111.903965&sspn=0.741203,1.231842&ie=UTF8&z=10 (http://maps.google.com/maps?f=d&source=s_d&saddr=Wellsville,+UT&daddr=42.002366,-111.958923+to:Swanlake,+ID&hl=en&geocode=FY9aewIddgZU-SlRIT3OO35ThzEDDwUd3FXv-Q%3B%3BFRClhQId-fRS-SlVRmge2ANVhzEb3ACzb96K3A&mra=dpe&mrcr=0&mrsp=1&sz=10&via=1&sll=41.975925,-111.903965&sspn=0.741203,1.231842&ie=UTF8&z=10)
This brings me to another question, somewhat unrelated--was there ever an ID-23 connecting to UT-23? I've seen a Cache Valley phone book which shows the Idaho portion as ID-23; would it be outdated or a typo of sorts?