Alternate vs. bypass

[Quillz]

In what context(s) would a route be designated as an alternate, as opposed to a bypass? I don't know if such designations are still given out, but they were fairly common in the early days of the US routes, and a few still exist.

Does it work akin to 3di, in that spurs function as alternates, and loops function as bypasses? Seems to be an alternate would be a route that serves some kind of satellite city or major suburb, while a bypass would entirely move around a major city, but nowadays, any such difference would be hard to spot.

[dgolub]

I've seen a lot more alternates than bypasses.  As far as I know, New Jersey has only one bypass in the entire state.  From what I've seen, both are generally loops rather than spurs.

In Rocky Point, there's a section where NY 25A splits into Business NY 25A and Bypass NY 25A, where the bypass is a super-2 and the business route runs through the town.  But Bypass CR 533 in New Jersey is just a surface road.

[jwolfer]

Alternate is usually longer. Not neccesarily faster, just a different routing.

Bypass is a shoter shortcut of usually one city or town. Florida usually calls bypasses Truck Route

LGMS428

[jp the roadgeek]

Alternates are usually short spur or loop routes that run near the parent route.  CT currently has 1 US alternate (US 1A) and 5 state alternates (2A, 14A, 17A, 71A, and 182A), but had many more in the past that have either been renumbered, demoted to SR status, or returned to local maintenance.

Bypasses are usually limited access highways that serve as a high speed alternate of passing through a large town or city.  CT has no officially signed bypass routes.  Only one I know of in New England is Bypass NH 28 near Manchester, NH.  US 6 used to be signed as Bypass US 6 in Scituate, RI, but current signage has it signed as US 6 proper and Danielson Pike through Scituate as Scituate Business Route without any reference to US 6.

[Brandon]

An alternate may not even be a bypass.  From 1940 to 1966, the old routing of US-66 through Joliet was Alternate 66 instead of Business 66.

[hotdogPi]

Only one I know of in New England is Bypass NH 28 near Manchester, NH.

There's a US 1 Bypass in Portsmouth, NH. It bypasses US 1, but I-95 is an even better bypass of US 1.

Massachusetts has 1A, 2A, 3A, 6A, 7A, 28A, 32A, 114A (from RI 114, not MA 114), 127A, 129A, 146A, and others. They are not faster than the original route.

[epzik8]

Alternates are usually second routings of a mainline and tend to be surface streets, while bypasses are usually specific to a town or city and are often limited-access.

[briantroutman]

In at least one case, ALT is used to keep a former alignment signed under its old number–which, coincidentally, is fitting if you know a little German.

The one I recall is ALT US 220 between Port Matilda and Milesburg, PA. 220 was re-routed along the new I-99 freeway through State College and Bellefonte while the old road through Bald Eagle Valley got the ALT banner. The ALT route isn't really a bypass, although it may be a convenient relief route on the Church of Penn State's high holy days

[roadfro]

From the AASHTO Transportation Policy Book, January 2000. (source: Establishment and Development of United States Numbered Highways, page 2)

SPECIAL ROUTE DEFINITIONS
...
By-Pass: A "By-Pass Route" or a "Relief Route" is a route which is established for the purpose of designating a route which entirely by-passes a city or congested area and joins in with the regular numbered route beyond the city or congested area. This enables the regular number to be carried both through the city and around the city without either designation carrying any other sign or lettering showing a preference.
...
Alternate Route: An "Alternate Route" shall be considered a route which starts at a point where it branches off from the main numbered route, may pass through certain cities and towns, and then connect back with the regular route some miles distant. Since it is the purpose of the U.S. numbered system to mark the best and shortest route available, an alternate route should be designated only where both routes are needed to accommodate the traffic demand and when the alternate route has substantially the same geometric and structural design standards of the main marked routing.

It is recommended that, in cases where an alternate route is marked, the shorter and better constructed route be given the regular number and the other section designated as the "Alternate Route." It is further recommended that the Highway Department erect signs at the junction points of the regular and alternate routes giving the distance between the cities or points
concerned.

In this context, alternate routes diverge from the mainline to serve populations slightly distant from the mainline, but then return to the mainline. Generally, quality of highway is comparable. A bypass just serves to route some traffic around one city.


To liken these to Interstate numbering:

• A Bypass route could be any even numbered 3di forming a half loop around a city, as long as the 3di returned to it's parent.
  
• For an Alternate route: Say Texas wanted to eliminate their I-35E/I-35W split. If they renumbered current I-35E through Dallas as the mainline I-35, I-35W through Fort Worth could be "Alt I-35".
  

[Road Hog]

For what it's worth, I-35E presently does maintain the parent I-35 mileage throughout.

[cpzilliacus]

Alternates are usually second routings of a mainline and tend to be surface streets, while bypasses are usually specific to a town or city and are often limited-access.

Alternate U.S. 40 in Washington and Frederick Counties in Maryland is the old routing of U.S. 40, and it shows, with some fairly sharp curves as compared to U.S. 40 along the same path, from Hagerstown to the west side of Frederick.

Current U.S. 40 bypasses all of the small towns in the area with only a few traffic signals (it's actually a pretty good bail-out route if there is a serious problem on I-70), while Alternate U.S. 40 goes through several incorporated and unincorporated places from Funkstown (outside Hagerstown) to Braddock Heights.

[PHLBOS]

Massachusetts has 1A, 2A, 3A, 6A, 7A, 28A, 32A, 114A (from RI 114, not MA 114), 127A, 129A, 146A, and others. They are not faster than the original route.

In many of those (but not all) instances, the XA represents the original or pre-expressway route; 3A being one example.

[sparker]

In regards to the two major "alternate" US highways in CA prior to the '64 renumbering, they did serve two different purposes:  Alternate US 101 in greater L.A./Orange/Ventura counties was a "recreational" route along the coast (as well as a convenient place to terminate US 6, US 66, and US 91 back then!) intended to provide a familiar designation to aid in tourism navigation (as opposed to its pre-1934 numbering as the original SSR 3).  Alternate US 40 through the Feather River Canyon was commissioned in 1953, largely replacing SSR 24; its designation followed the terrible winter conditions of 1952 affecting the US 40 Donner Pass segment that resulted in multiple closures of that route (and the several-day stranding of the SP "City of San Francisco" passenger train adjacent to the highway).  An alternate route at lower elevation was deemed advisable, so Alternate US 40 was signed in the summer of '53 and remained in place until the '64 renumbering.

The "Alternate US 66" (1940-64) route between central L.A. and Pasadena was the last iteration of US 66 between those places before it was moved to the Arroyo Seco Parkway; it was the alignment of the "old" route, intended to serve as a local truck route to keep such traffic away from the parkway.

With "bypass" routes (primarily concerning US 101), the one from East Los Angeles SE to Anaheim was a postwar effort to reroute truck traffic away from Whittier Blvd (after complaints from Whittier and La Habra) until the Santa Ana Freeway could be completed.  The Bay Area version of Bypass US 101 along the Bayshore Freeway lasted until, again, the '64 renumbering, when bannered routes were deleted.   The other "bypass", for US 50 southeast of central Sacramento, used Avenue 14 east from Stockton Blvd. (then US 50/99) to 65th Street, and 65th north to Folsom Blvd. (US 50/SSR 16) as a "convenience" cutoff for US 50 traffic, as the main route took a convoluted path through the downtown area.  It was part of LRN 98, which extended north from US 50 via Elvas Ave., Fair Oaks Blvd., and Fulton Ave. to US 40/99E (Auburn Blvd.) in the Arden/Arcade area NE of the central Sacramento area; the portion between the US 50 segments was signed as "Bypass US 50" until LRN 98 was moved to the Elvas Freeway and the 29th/30th street couplets (US 99E) in the early '50's.  Once the bypass was relinquished, the signage remained in place but was gone by the time the South Sacramento (then US 50/99) freeway was opened in 1961. 

[ekt8750]

PA uses ALT Truck routes to divert overweight/overheight trucks away from low underpasses and weight restricted bridges.

[TR69]

ALT US 60 in Louisville is a good example. While it "bypasses" downtown, it never leaves the city, so it is truly just an alternate route to the mainline US 60 (which does go through downtown).

[hbelkins]

ALT US 60 in Louisville is a good example. While it "bypasses" downtown, it never leaves the city, so it is truly just an alternate route to the mainline US 60 (which does go through downtown).

There's an odd history about US 60 in Louisville, the details of which I cannot recall offhand. The Watterson Expressway was built as a freeway bypass of Louisville for US 60; in my youth it was co-signed with I-264 and the routing of US 60 through downtown was signed as Business US 60. I almost think that prior to the Watterson, Alt. 60 was just plain 60 and Business 60 ran through downtown similarly to the way it does now.

[Bitmapped]

PA uses ALT Truck routes to divert overweight/overheight trucks away from low underpasses and weight restricted bridges.

PennDOT normally just signs them as TRUCK routes (no ALT).

[capt.ron]

In Alabama, ALT 72 is actually shorter than the mainline 72 if you're heading east towards Huntsville. It's only slow going through Town Creek and Decatur but other than that, its full speed ahead. More of it is divided vs mainline 72.
It would make more sense if the routes were flipped, but that is a topic for another day...

[74/171FAN]

PA uses ALT Truck routes to divert overweight/overheight trucks away from low underpasses and weight restricted bridges.

PennDOT normally just signs them as TRUCK routes (no ALT).

District 6 refers to them as ALT Truck Routes for some reason.  I have not seen the ALT banner with them anywhere else in PA.

[hbelkins]

In Alabama, ALT 72 is actually shorter than the mainline 72 if you're heading east towards Huntsville. It's only slow going through Town Creek and Decatur but other than that, its full speed ahead. More of it is divided vs mainline 72.
It would make more sense if the routes were flipped, but that is a topic for another day...

But the Florence/Muscle Shoals stretch of 72 is a congestion and traffic signal nightmare. That's why the alternate route is a much better choice for through traffic.

[briantroutman]

District 6 refers to them as ALT Truck Routes for some reason.  I have not seen the ALT banner with them anywhere else in PA.

How much autonomy to districts have in matters like this–deciding to sign a route as ALT vs. TRUCK?

As an uninformed outsider, I would have assumed that matters like this are decided in decided in Harrisburg and merely implemented by worker bees at the local engineering districts, but I gather that's not the case.

[74/171FAN]

District 6 refers to them as ALT Truck Routes for some reason.  I have not seen the ALT banner with them anywhere else in PA.

How much autonomy to districts have in matters like this–deciding to sign a route as ALT vs. TRUCK?

As an uninformed outsider, I would have assumed that matters like this are decided in decided in Harrisburg and merely implemented by worker bees at the local engineering districts, but I gather that's not the case.

First off, to solve any confusion they actually are signed "ALT TRUCK" in District 6.  There is even a US 30 BUS ALT TRUCK that uses the US 30 freeway around Downingtown.

My best guess is that District 6 decided to add an extra to the minimum required in this case.  I found no mention of ALT TRUCK in Pub 46 (Traffic Engineering Manual).

[Quillz]

District 6 refers to them as ALT Truck Routes for some reason.  I have not seen the ALT banner with them anywhere else in PA.

How much autonomy to districts have in matters like this–deciding to sign a route as ALT vs. TRUCK?

As an uninformed outsider, I would have assumed that matters like this are decided in decided in Harrisburg and merely implemented by worker bees at the local engineering districts, but I gather that's not the case.

South Dakota recently opened a segment of US-16 that was specifically labeled as "TRUCK," even though in practice it would be a bypass. It was near the Rapid City area, IIRC, so perhaps its a city council decision?

[Aerobird]

An alternate may not even be a bypass.  From 1940 to 1966, the old routing of US-66 through Joliet was Alternate 66 instead of Business 66.

This would apply to Alternate US-19 in Pinellas County, Florida. It goes through the "old town centers" while US-19 itself runs through what would, Way Back In The Day, have been a bypass (by no means at ALL now of course-)

In at least one case, ALT is used to keep a former alignment signed under its old number–which, coincidentally, is fitting if you know a little German.

This was used on what was, at one time, Alternate US-319 in northwest Florida. The route once ran down what is now FL-363 and CR-365/CR-61 between Tallahassee and Crawfordville. When it was switched to its current alignment, the original one was maintained as  ALT-319 for awhile, before being fully decommissioned.

[mapman1071]

In AZ Uses A or Alternate for both State and US Route 89 (US 89 Goes Thru Page and Glen Canyon/Lake Powell and US 89A Goes across the Eastern portion of the Arizona Strip meeting back to US89 at Knab, UT (LOOP) AZ 89 & AZ89A Split At Prescott but does not meet again. AZ 89 ends at I-40 in Ash Fork, AZ 89A Ends at Business I-40/US66 in Flagstaff.

AZ 79 does have a Business AZ 79 that Loops thru Downtown Florence.