This plaque, printed on an orange construction sign blank, had no obvious meaning to me at first. Soon after this gallery was posted, Marc from Roadfan.com wrote to me with a little bit of background on the meaning of this: "Michigan has Emergency I-94 routings running parallel to I-94 from its entrance from Indiana eastward almost to Ann Arbor, to detour traffic in case of road closures, especially those caused by lake effect snow on the western end. There is also an Emergency US-31 near Muskegon. These are similar to the colored detours in Pennsylvania." He also noted that these plaques are usually printed with white lettering on a blue background. Thanks Marc!