The Michigan Department of Transportation (MDOT) maintains M-120 like all other components of the Michigan state trunkline highway system. As part of these responsibilities, the department tracks traffic volumes along the highway. MDOT uses a metric called average annual daily traffic, which is a calculation of the traffic along a roadway segment for any average day of the year. In 2009, the highest traffic levels were near the southern terminus at 26,736 vehicles each day. The lowest levels MDOT calculated were in Holton at 5,936 vehicles daily. The section between the south end and US 31, M-120 has been listed on the National Highway System, a network of roads important to the nation's economy, defense, and mobility. The remainder of the highway has not been listed.