 As a part of these maintenance responsibilities, the department tracks the volume of traffic that uses the roadways under its jurisdiction.These volumes are expressed using a metric called annual average daily traffic, which is a statistical calculation of the average daily number of vehicles on a segment of roadway.MDOT's surveys in 2011 showed that the highest traffic levels along M-139 were the 12,248 vehicles daily between the intersections with Fairland and Deans Hill/Pokagon roads south of Berrien Springs; the lowest counts were the 1,576 vehicles per day in downtown Niles.