Question Unless otherwise posted, the speed limit on interstate highways is: Answers 55 mph. 65 mph. 75 mph. Explanation When driving on an interstate highway, the speed limit is 65 miles per hour. If a different speed limit is posted, follow the posted speed limit. Pass your DMV Written Test with flying colors Take me to the cheat sheet Kentucky This questions appears in the following tests: Kentucky Practice Test 12 Kentucky Practice Test 28