State railways. Running immediately next to the river, M-13 meets I-75/US 23 at that freeway's exit 153 just southeast of the Zilwaukee Bridge. The highway runs along Bay City Road as it continues to follow the Saginaw River through the Crow Island State Game Area. On the south side of Bay City, the name changes to River Road. M-13 passes the James Clements Municipal Airport and transitions to follow Broadway Street into downtown. At Lafayette Street, M-13 turns west and merges with M-84. The two highways run concurrently across the Saginaw River on the Lafayette Avenue Bridge. The structure's two spans connect the riverbanks with the Middle Ground Island in the center. West of the bridge, M-13/M-84 follows Salzburg Avenue to the intersection with Euclid Avenue. At that location, M-13 turns north along Euclid Avenue, which runs along the western city line. M-13 meets the 2 one-way streets that carry M-25 and the I-75 business spur at the intersections with Thomas and Jenny streets. From this intersection on, M-13 forms a part of the Lake Huron Circle Tour. Farther north, the highway turns northwesterly on Huron Road; Euclid Avenue continues north as M-247. As the trunkline heads away from Bay City, it runs parallel to the Lake State Railway again. M-13 intersects the northern end of its connector route before Huron Road crosses the Kawkawlin River. The highway runs through the community of the same name on the north side of the river. M-13 and Huron Road continue north across mixed agricultural and forest land as they pass through the communities of Linwood and Pinconning. South of Standish in Arenac County, M-13 meets the northern end of the US 23 freeway and terminates. M-13 is maintained by the Michigan Department of Transportation (MDOT) like other state highways in Michigan. 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 2009 showed that the highest traffic levels along M-13 were the 28,242 vehicles daily north of the M-25 junction in Bay City; the lowest counts were the 3381 vehicles per day south of the I-75/US 23 interchange near Saginaw. The only sections of M-13 that have been listed