The following information is excerpted directly from WisDOT's "Traffic Guidelines Manual," Chapter 2, Section 4, Subject 19.1:
The Business Route Marker is an auxiliary marker used to identify Business Routes which have been established pursuant to either Section 84.02(4) or 84.02(6) of the Statutes. The latter section terms them Alternate Routes, but they shall be signed as Business Routes.
Business Route establishment begins with a locally initiated request to [a WisDOT] District office. The District shall require that the request come from a municipal official or body of the local community, not an association or chamber of commerce, etc. The District shall request information on the appropriateness of the route, the unity of community regarding the location and service provided, the structural and geometric adequacy of the route, the adequacy of the traffic control, and such other factors as may be pertinent.
If the District office finds the establishment to be in the interests of the motoring public it shall make a favorable recommendation to the State Traffic Engineer, who shall have the authority for approval.
When the approved route falls completely upon the existing state trunk highway and connecting highway system the Department will initially install and subsequently maintain all route marking.
When all or any portion of the approved route is on local streets or highways, including county trunk highways, the Department will agree to install the initial markers, but subsequent maintenance of the markers will be the responsibility of the community. The Department will however maintain those markers at the beginnings of the route which face traffic on the regular state trunk highway route.
Failure of the city or village to properly maintain the signs or to comply with other conditions of the approval will be cause for the Department to withdraw approval and remove the signs. District offices will be responsible for periodically inspecting the condition of all signs to ensure that they are kept in good condition.
If a business route is proposed related to a U.S. Highway designation the route has to have the approval of AASHTO. [In these cases, WisDOT personnel are instructed to] contact the central office Bureau of Highway Operations for instructions regarding this approval.
In 2004, WisDOT apparently conducted a program of eliminating signed business connections in urbanized areas around the state. For example, in August of that year, the City of Manitowoc Streets & Sanitation Committee recieved a letter from the department requesting the removal of business route designations through urbanized areas, in this case specifically BUS STH-42 in Manitowoc. Committee minutes note that WisDOT "claim[ed] these designations are confusing to some drivers." Furthermore, the committee members felt the business route made it easy to give directions to motorists unfamiliar with the area and were also worried about loss of funding.
While no action seems to have been taken in the Manitowoc case, this program likely caused the removal of the remainder of the business route signage in places like Appleton, Green Bay, Oshkosh and other cities. Even in some instances where business connections remain in more urbanized locations, such as Janesville and Chippewa Falls, WisDOT is no longer labeling these routes as such on its official state highway map.