Question Unless otherwise posted, the speed limit on state highways is: Answers 25 mph. 35 mph. 45 mph. 55 mph. Explanation Unless otherwise posted, the speed limit on state highways is 55 mph. If a different speed limit is posted, you should follow that speed limit. Pass your DMV Written Test with flying colors Take me to the cheat sheet Michigan This questions appears in the following tests: Michigan Practice Test 3 Michigan Practice Test 30