 As part of its maintenance duties , the Michigan Department of Transportation ( MDOT ) tracks the volume of traffic on the highways it maintains . This number is expressed in terms of annual average daily traffic ( AADT ) , a calculation of the average traffic for a segment of roadway on any average day of the year . In 2009 , the department measured a peak of 19 @,@ <unk> vehicles daily on the stretch north of <unk> Road . The section south of the US 10 interchange had the lowest traffic level at 9 @,@ 315 vehicles AADT . Additionally , entire route of M @-@ 47 has been listed on the National Highway System , a network of roads important to the country 's economy , defense , and mobility . 
