<P> Every Labor Day, the bridge is open to walkers for the Mackinac Bridge Walk . </P> <P> Painting of the bridge takes seven years, and when painting of the bridge is complete, it begins again . The current painting project began in 1999 and was expected to take 20 years to complete because the lead - based paint needs to be removed, incurring additional disposal requirements . </P> <P> The bridge celebrated its 150 millionth vehicle crossing on September 6, 2009 . </P> <Ul> <Li> Length from cable bent pier to cable bent pier: 7,400 feet (2,256 m). </Li> <Li> Total width of the roadway: 54 feet (16.5 m) <Ul> <Li> Two outside lanes: 12 feet (3.7 m) wide each </Li> <Li> Two inside lanes: 11 feet (3.4 m) wide each </Li> <Li> Center mall: 2 feet (0.61 m) </Li> <Li> Catwalk, curb and rail width: 3 feet (0.91 m) on each side </Li> </Ul> </Li> <Li> Width of stiffening truss in the suspended span: 68 feet (20.7 m). </Li> <Li> Depth of stiffening truss: 38.1 feet (11.6 m) </Li> <Li> Height of the roadway at mid-span: approximately 200 feet (61 m) above water level . </Li> <Li> Vertical clearance at normal temperature: <Ul> <Li> 155 feet (47 m) at the center of the main suspension span . </Li> <Li> 135 feet (41 m) at the boundaries of the 3,000 feet (914 m) wide navigation channel . </Li> </Ul> </Li> <Li> Construction cost: $99.8 million (equivalent to $669 million in 2016) </Li> <Li> Height of towers above water: 552 feet (168 m) </Li> <Li> Max . depth of towers below water: 210 feet (64 m) </Li> <Li> Depth of water beneath the center of the bridge, 250 feet (76 m) </Li> <Li> Total length of wire in main cables: 42,000 miles (68,000 km). </Li> <Li> Total vehicle crossings, 2005: 4,236,491 (average 11,608 per day) </Li> <Li> Speed limit: 45 miles per hour (72 km / h) for passenger cars, 20 miles per hour (32 km / h) for heavy trucks . Heavy trucks are also required to leave 500 feet (150 m) spacing ahead . </Li> </Ul>

What is the longest bridge in the western hemisphere