 Because the bridge normally only allows motor vehicles, bicyclists and snowmobiles shuttled across are subject to fees.The authority maintains a small police department to patrol the bridge and escort vehicles across, and a pair of radio station transmitters that broadcast bridge conditions and travel information on AM 530 and AM 1610.North of the Mackinac Bridge, I-75 passes to the west of downtown St. Ignace, traveling between the Father Marquette National Memorial and Straits State Park.