MI HB4425

Allows county road commissions, township boards, and the Department of State Police to unanimously establish reasonable speed limits on county highways based on engineering and traffic investigations.

Permits township boards to petition county road commissions or county boards of commissioners for speed limit changes, advisory signs for hazardous conditions, or changes without requiring a formal speed study.

Requires speed limits to be determined by the 85th percentile speed of free-flowing traffic rounded to the nearest 5 mph, with minimum posting at the 50th percentile speed.

Authorizes the state transportation department and Department of State Police to jointly determine speed limits on limited access freeways and trunk line highways, with public records filed at the county clerk's office.

Classifies violations of established speed limits as civil infractions and requires signs to conform to Michigan's manual on uniform traffic control devices.