In Michigan, speed limits are set after a traffic study is done by the County Road Commission.  Once the traffic study is completed, there is a formula used by the County Road Commission, The State Police and recently the Township. This formula ensures continuity across the State for establishing speed limits on roads.

                                      Please click on the following links for more information:
                                         Livingston County Road Commission Speed Limits
                                     Michigan State Police Establishing Realistic Speed Limits