While the original intent and still a major focus of the Michigan Highways website was to catalog the various numbered Interstate, US and State-designated highways, there are other types of marked routes in Michigan. Some of the "other" routes are posted along the state trunklines, while others have nothing to do with the state-maintained system of highways. Because of this, the signing of some of these "other" types of highways may be less than thorough and detailed maps may need to be consulted in order to follow them.
- Unsigned State Trunklines – The vast majority of state trunklines in Michigan carry one or more route number designations. A few, though, either have no route number or the route designation is "secret"—not posted along the highway and, thereby, not generally known to the public. This page details those highways.
- Great Lakes Circle Tours – The Great Lakes Circle Tours are marked routes circling four of the Great Lakes, with Michigan hosting portions of each. This portion of the website details each of these.
- Forest Highways – providing all-weather access to National Forest areas, these routes are generally well-maintained facilities. Many Forest Highways in Michigan, however, are unsigned in the field.
- Pure Michigan Byways (Heritage Routes) – renamed from Heritage Routes in 2014, these byways are signed along state trunklines and point to Historic, Recreational or Scenic opportunities.
- Polar-Equator Trail – The P-E Trail was signed by a group affiliated with Michigan State University and seems to be slowly fading into the past. This portion of the website attempts to capture the story of this route before it is lost forever.