 North of this freeway interchange , M @-@ 18 is also the route of Business Loop I @-@ 75 ( BL I @-@ 75 ) . The combined BL I @-@ 75 / M @-@ 18 runs north near the Roscommon Conservation Airport and turns northeasterly into town . In the middle of Roscommon , BL I @-@ 75 turns northwest along Old 76 Road , and M @-@ 18 continues northeasterly across a line of the Lake State Railway . The highway continues independently to the northwest over the South Branch of the Au Sable River and out of town . It then turns due east along the Roscommon – Crawford county line . This section of the county line also forms the southern boundary of the Huron National Forest . M @-@ 18 curves to the northeast off the county line into the national forest territory where it meets F @-@ 97 for a second time . At this junction , F @-@ 97 merges with M @-@ 18 and the two roads run due north to a junction with M @-@ 72 west of Luzerne . At this intersection , F @-@ 97 continues north and M @-@ 18 terminates in rural Crawford County . 
