I was recently looking for a place to kayak in Southern Michigan, when the link for the map led me to the town of Middleville, MI. At first glance I was like ok, the town isn't too far out of way for a trip in the summer. Then I looked again and saw a US Highway Shield for US 37. I traced it to it's southern terminus just west of Battle Creek, MI and it's northern terminus just south of Traverse City, where it ends at US 31. According to Wikipedia, it has been commissioned for 31E through Kentucky, but no mentions of through Michigan. Is there an error on Google's end or has it recently been commissioned through Michigan?
*If this is old news I apologized, I searched the forums with no luck of this being mentioned before*
It's an error. The route is M-37.
Always double-check another map before trusting Google Maps whenever you find anything unusual!
Maps have errors. Deal with it.
Somewhere on this forum is a thread about Google Maps errors, in which I believe this issue has been mentioned already.