Traffic control: speed restrictions; determination in accordance with traffic engineering practices; modify. Amends sec. 628 of 1949 PA 300 (MCL 257.628).

HB 4137 updates Michigan’s speed limit rules to require local governments to set limits based on actual traffic speeds and safety data. It mandates that speed limits be determined using traffic engineering practices, rounded to the nearest 5 mph, and generally align with the 85th percentile speed of free-flowing traffic on a road segment. Exceptions allow lower limits (down to the 50th percentile) only when safety hazards are proven through engineering studies. This directly affects county road commissions, township boards, and city officials responsible for setting speed limits on local roads and highways.