leaving the M-72 concurrency to continue northward. M-33 crosses into the Mackinaw State Forest and passes through Comins. North of that unincorporated community, the highway curves northeast, east and back north to cross into Montmorency County. Before reaching M-32, M-33 crosses the Thunder Bay River. After the river, M-33 turns westward along M-32 to the community of Atlanta. The highway passes near the Atlanta Municipal Airport as it enters the community. In the middle of town, M-33 turns back north. The highway provides access to the Clear Lake State Park in northern Montmorency County before crossing into Presque Isle County. M-33 parallels the Cheboygan – Presque Isle county line as it runs northward along the Black River to Onaway. Once in town, M-33 turns west with M-68 toward Cheboygan County. The highway passes through Tower, and a junction with F-05, before it continues west to the Afton area. There M-33 turns north one last time, running along the east shore of Mullett Lake past Aloha and M-212; M-212 is the shortest highway in Michigan that provides access to Aloha State Park. North of Aloha, M-33 crosses the Cheboygan River and meets M-27, the location of its northern terminus south of Cheboygan. The Michigan Department of Transportation (MDOT) maintains M-33 like all other state trunkline highways in the state. As a part of these maintenance responsibilities, the department tracks traffic volumes using a metric called average annual daily traffic (AADT). This figure is a calculation of the traffic along a roadway segment for any average day of the year. In MDOT's surveys in 2009, they found that the peak AADT along M-33 was the 6,928 vehicles a day along a section of the M-72 concurrency. The lowest traffic counts were measured immediately south of the Onaway city limits at 956 vehicles daily. The only section of M-33 that has been listed on the National Highway System (NHS) is the segment concurrent with M-32 in Montmorency County. The NHS is a network of roads important to the country's defense, economy and mobility. History M-33 was first designated by July 1, 1919. It ran along the current routing from Mio north to M-32 east of Atlanta. The highway also ran south of Mio to M-76 east of Roscommon using segments of what are now M-72 and M-144. By 1927, the southern section from Fairview to Roscommon was redesignated as a part of M-72.