Interstate Business Route Guides

The following lists show all system-wide Interstate business routes currently signed and previously posted. Within the following tables, "retired" denotes decommissioned business routes, "active" denotes currently maintained or signed business routes, "proposed" indicates the business route may have been proposed at one time or is a future route and "unsigned" means the loop or spur is officially recognized but is not signed in the field.

Interstate 5 Interstate 30 Interstate 75
Interstate 8 Interstate 35 Interstate 76
Interstate 10 Interstate 40 Interstate 80
Interstate 15 Interstate 44 Interstate 82
Interstate 17 Interstate 45 Interstate 83
Interstate 19 Interstate 49 Interstate 84
Interstate 20 Interstate 55 Interstate 85
Interstate 24 Interstate 57 Interstate 86
Interstate 25 Interstate 65 Interstate 89
Interstate 26 Interstate 69 Interstate 90
Interstate 27 Interstate 70 Interstate 94
Interstate 29 Interstate 72 Interstate 95
Interstate 96

Interstate 64 is the longest primary Interstate without any business loops or spurs. Business Interstates were never assigned for the following routes:

Interstate 2 Interstate 43 Interstate 78
Interstate 4 Interstate 59 Interstate 79
Interstate 12 Interstate 64 Interstate 81
Interstate 16 Interstate 65 Interstate 86
Interstate 22 Interstate 66 Interstate 87
Interstate 26 Interstate 68 Interstate 88
Interstate 37 Interstate 71 Interstate 91
Interstate 39 Interstate 73 Interstate 93
Interstate 41 Interstate 74 Interstate 97
Interstate 42 Interstate 77 Interstate 99

Purposes of Interstate Business Loops and Spurs

Interstate business connections (loops and spurs) were approved by AASHTO in 1964 as a method to provide access from the Interstate superhighway to the cities and towns bypassed by the freeway. AASHTO made this decision during the height of Interstate highway system construction. While primarily geared toward U.S. Highway business routes, AASHTO Policy HO1 defines a business route as "a route principally within the corporate limits of a city which provides the traveling public an opportunity to travel through that city, passing through the business part of the city, while the regular number is used to obviate passing through the congested part of the city. This 'Business Route' connects with the regular numbered route at the opposite side of the city limits. 'Business Route' numbering shall be established by the placing of a standard strip carrying the words 'Business Route' on the staff above the U.S. shield." Business routes are marked with a white on green variation of the standard tri-color Interstate shield.

As the Interstate Highway System neared completion, business routes became more prevalent. Business loops were commissioned in some areas where the U.S. route still existed as a means to entice travelers to exit and use services available in that town or city. These routes consisted of surface streets through the city center, older arterial bypasses around the city, divided highways with some grade separated interchanges and other non-limited access routes.

Business Interstates are most often posted in the western states, across the Great Plains and in Michigan. Eastern states generally did not designate business loops, as most of the Interstates paralleled the original U.S. routes instead of directly replacing them. With the exception of mountainous areas, this left most of the U.S. highways in place, or as co-signed routes with the parent Interstate, while the former routes were redesignated as local or frontage roads. In contrast, construction of the Interstate system in the western states often directly overlaid the old U.S. highway, leaving the former road impassable or as a disconnected route. Exceptions were at cities and towns, where the freeway would shift onto a bypass around them. This often left extant segments of old U.S. Highways in place, with a business loop designation applied to them as a motorist aid to and from a business district of collection of motorists services.

Implementation and maintenance of business routes varies from state to state. States like Illinois, Michigan and Wyoming incorporate Interstate business routes within the state maintained system. These routes tend to be well signed given their status as state routes/highways. Other states like California usually transfered responsibility for business route maintenance to a local municipality when the bypass route (Interstate mainline) was completed. Local maintenance includes posting signs and replacing them as needed. Some states such as Nevada, South Dakota and Washington allow business loops to fall under local control by cities and counties while also maintaining others as state routes.

Types of Business Routes

There are five basic types of business connections:

  1. Business Loops that replaced a decommissioned U.S. route. Examples include:
    • The I-5 business loops in northern California replaced U.S. 99W through towns such as Woodland, Arbuckle, Williams, Willows, Orland, Red Bluff and Redding.
    • The I-15 business loops in Utah overlaid old U.S. 91 through cities such as St. George, Cedar City, Parowan, Beaver and Nephi. Notably, most business loops in Utah are cosigned with a different state highway route number.
    • The I-55 business loops in Illinois replaced U.S. 66 through the cities of Springfield, Bloomington-Normal and Lincoln.
    • The I-94 business loops across North Dakota were designated along former U.S. 10 through Dickinson, Mandan, Bismarck and Valley City.
  2. Business Loops from Interstates cosigned with a U.S. Route. Examples include:
    • The I-25 business loops in Wyoming, which provide direct access from the freeway to the original U.S. 87 route through cities such as Cheyenne, Wheatland, Douglas, Casper and Buffalo. Business routes in Wyoming are usually cosigned with U.S. Business routes from the parent route.
    • Business Loop I-70 in Denver follows U.S. 40 across the metropolitan area while a second in Limon runs concurrent with U.S. 40 through Limon.
  3. Business Loops that are from Interstates paralleled by a U.S. Route. Examples include:
    • The I-75 business loops in southern Georgia, which connect to and supplement U.S. 41 through cities such as Tifton and Cordele.
    • Business Loop I-15 through Pocatello, Idaho overlaps with U.S. 91 and 30.
    • Business Loop I-40 through Amarillo, Texas doubles as U.S. 60 across the east side of the city.
  4. Business Spurs from Interstate into City/Destination. Examples include:
    • Business I-20 Spur from the I-20/95 junction into Florence, South Carolina.
    • Business I-44 Spur into Fort Leonard Wood, Missouri.
  5. Business Loop Freeways. With the designation of Business Loop I-80 in Sacramento in 1981, a fifth type of business connection was created: the business loop freeway. There are currently four across the system:
    • Business Loop I-40 through Winston-Salem, North Carolina
    • Business Loop I-80 through Sacramento, California
    • Business Loop I-85 by Spartanburg, South Carolina
    • Business Loop I-85 through Greensboro, North Carolina
    The Business I-495 Spur Freeway into Lowell, Massachusetts was the lone spur within this category.

The following sections show how certain states identify and designate business routes. The 2009 Manual on Uniform Traffic Control Devices (MUTCD) for Streets and Highways provides guidance on a wide variety of standards used for roads, including business routes. Page 143 provides pertinent information about business routes: "Standard: 05 Off-Interstate Business Route signs (see Figure 2D-3) shall consist of a cutout shield carrying the number of the connecting Interstate route and the words BUSINESS and either LOOP or SPUR in upper-case letters. The legend and border shall be white on a green background, and the shield shall be the same shape and dimensions as the Interstate Route sign. In no instance shall the word INTERSTATE appear on the Off-Interstate Business Route sign. Option: 06 The Off-Interstate Business Route sign may be used on a major highway that is not a part of the Interstate system, but one that serves the business area of a city from an interchange on the system. 07 When used on a green guide sign, a white square or rectangle may be placed behind the shield to improve contrast."

Interstate Business Routes in Arizona

Prepared and updated by the Arizona Department of Transportation (ADOT), the State Highway System Log, provides updates on the status of all Arizona state highways, including business loops and spurs.

Arizona has studied the removal of nonessential business routes from the state highway system. ADOT Route Transfer Procedures Study from June 2012 states that "Priorities for route transfer are: ... c) Existing business routes not necessary for system continuity." Unlike some other states, Arizona generally will not sign business loops on non-state maintained roadways.

Interstate Business Routes in California

Within California, business routes are specifically designated based on the requirements specified in the following passage from the California Highway Design Manual (revised May 2012). Chapter 20 ("Designation of Highway Routes") of the design manual indicates that by definition, a business route is a loop through a city or town rather than a spur:

(4) Business Routes. A Business Route generally is a local street or road in a city or urban area, designated by the same route number as the through Interstate, U.S., or State highway to which it is connected, with the words "Business Route" attached to the identifying route shields. The Business Route designation provides guidance for the traveling public to leave the main highway at one end of a city or urban area, patronize local businesses, and continue on to rejoin the main route at the opposite end of the city or urban area. The Transportation System Information Program is responsible for approval of Business Route designations. Applications for Business Route designation and signing must be made by written request from the local government agency to the Chief of the Transportation System Information Program. U.S. and Interstate Business Routes require approval by the AASHTO Executive Committee.

Furthermore, California has standards that are unlike those of other states. Joe Rouse provided the official policy on business route signing in California from the state Traffic Manual:

The ROUTE ## BUSINESS sign may be used to direct motorists to an established U.S. or State numbered business route or an Interstate business loop from a State highway. The plate should be installed below an advance ground-mounted directional sign. The sign may be placed separately in advance of the business route if it is necessary. A NEXT RIGHT/LEFT message may be used on expressway and conventional highway installations. A NEXT EXIT message may be used on freeways.

The INTERSTATE BUSINESS LOOP sign may be used to advise motorists of an established Interstate business loop. The sign should be installed on the right on the loop. It should not be placed on the Interstate route itself. The ROUTE ## BUSINESS plate should be used for advanced signing on the Interstate route.

The BUSINESS plate, in appropriate color, may be used to indicate an alternate route that branches from a US or State sign route, passes through the business district, and rejoins the route. The plate should be placed above the ROUTE SHIELD sign. The INTERSTATE BUSINESS LOOP sign should be used on an interstate business loop. The ROUTE ## BUSINESS plate should be used for advanced signing on U.S. or State sign routes.

Finally, here is Caltrans' policy on establishing business routes per the Caltrans Traffic Manual - Section 2D.09 Numbered Highway Systems (page 321):

State business routes and Interstate Loops are established by the District Directors. U.S. business routes require AASHTO approval. Applications may be made by memorandum and shall include a written request for the route from those local agencies within and whose boundaries the route traverses. A sketch, preferably on letter size stationary, showing the highway relocation and the business route or loop, should be included. Submission for AASHTO approval will be made by Headquarters. Continuous business route signing shall be provided through the bypassed area and back to the highway. If a business route is approved prior to relinquishment, G55 Business plates or G31 Interstate Loop shields will be installed by Caltrans. After relinquishment, they will be installed by the local agency involved.

Interstate Business Routes in Colorado

Research from The Highways of Colorado webmaster Matt Salek revealed that the CDOT route logs inventory Interstate Business Loops and Spurs only if they are not concurrent with another numbered highway. An exception occurs with the Grand Business Loop for I-70, which overlaps with U.S. 6 & 50 to the west and U.S. 6 again to the east. Additionally CDOT also has a system of unmarked business spurs, which act as minor or major collectors between the parent freeway and a city or town.

Interstate Business Routes in Michigan

The Michigan Department of Transportation defines business routes as follows:

  • Business Loop (BL) - A business loop is a surface route that leads into a downtown business district and returns to the freeway at the other end. Frequently, the business loop is the alignment of the original highway before that highway was bypassed.
  • Business Route (BR) - A business route connects the freeway or through highway with the downtown and commercial areas of a city or town. Business routes are primary arterials and begin and end on the Interstate. Business Loops and Business Spurs are types of Business Routes. Business Loop implies that the business route will return to the parent route, while a business spur implies that the business route will only spur into the commercial area and not return to the parent route.
  • Business Spur - A business spur is a surface street route leading from the Interstate highway into the central commercial district. The spur route ends upon reaching a specified point within that urban area.

Interstate Business Routes in New Mexico

All Interstate business routes within the Land of Enchantment are inventoried on the New Mexico Department of Transportation (NMDOT) Posted Route - Legal Description lists. Routes are identified with a unique number separate from Interstates 10, 25 and 40. 11 total routes remained under state control as of March 16, 2010.

Interstate Business Routes in Utah

Utah also has unique standards that do not conform to other states with respects to business routes. Utah's UDOT Policy 06C-32 "Off-Interstate Business Loops and Spurs" (from 1973 and revised 2006) provides for certain minimum standards before a business route may be designated. Within the state of Utah, Off-Interstate Business Loops must:

  • Be located directly off of the Interstate system in rural areas outside the boundaries of any Municipal Planning Organization (MPO)
  • Follow a route where three or less interchanges serve the area
  • Have a length of six miles or less
  • Be traversable by all legal vehicles
  • Be appropriately signed
  • Connect two interchanges

Within the state of Utah, Off-Interstate Business Spurs must:

  • Not exceed three miles in length
  • Be traversable by all legal vehicles
  • Be appropriately signed

The policy continues by stating that "Signing shall conform to the most recent edition of the Manual on Uniform Traffic Control Devices (MUTCD). The Off-Interstate Business Route signs will be placed on the Interstate interchange guide signs, and trailblazing signing will be placed along the loop or spur. Only one set of Off-Interstate Business Route signs will be placed for each direction of travel on the Interstate."

Minimum standards for motorist services are also required prior to designation of a business loop or spur in Utah. For example, at least two gas stations must be open at least 16 hours per day seven days per week. The gas stations must provide fuel, oil, water, modern sanitary facilities, drinking water, and a public telephone. Additionally, at least one restaurant that operates continuously at least 14 hours per day, seven days per week, serving three meals per day, licensed by the appropriate public agency, with modern sanitary facilities and with the primary business purpose of preparing food must be located along the business route. Finally, a motel or hotel with at least ten rooms (with private modern sanitary facilities, licensed by the appropriate public agency, with a public telephone) must be located along the Utah business route.

This policy explains why most Utah off-Interstate business route are found in the less populated areas of the state and generally not among the communities of the Wasatch Front.

According to Dan Stober, UDOT specifies a state route counterpart for all Interstate Business Routes posted in the state. This may incorporate one or more routes. The state maintained highways see business route markers posted from the freeway toward the city center or business district and Interstate trailblazers leading back to the parent freeway. Wyoming and several other states also adheres to this signing practice.

Interstate Business Routes in Washington

Mark Bozanich provided some background on the use of Interstate Business Routes in the Evergreen State: "For the most part, business routes in Washington State are not part of the state highway system. It is harder for the state to get counties and cities to cooperate in posting signs along business routes than to post signs that are on state highways." So while the business routes are generally locally maintained, the city and county governments are less likely to maintain consistent signage or replace signs as needed. Additionally signs posted on roads and streets intersecting Business Loops and Spurs for the route intersected tend to be omitted.

Page Updated September 1, 2016.