Below is a NASA image and map of the Straits of Mackinac, which runs between the Lower Peninsula and Upper Peninsula of Michigan.
I went right to the web page published by the Macinac Bridge Authority to find out more about the bridge: http://www.mackinacbridge.org/
The Mackinac Bridge is currently the fifth longest suspension bridge in the world and the longest in the western hemisphere. In 1998, the Akashi Kaikyo Bridge in Japan became the longest with a total suspension of 12,826 feet. The total length of the Mackinac Bridge is 26,372 feet. The length of the suspension bridge (including anchorages) is 8,614 feet. The length from cable bent pier to cable bent pier is 7,400 feet. Length of main span (between towers) is 3,800 feet.
The height of the roadway at mid-span is approximately 200 feet above water level. The vertical clearance at normal temperature is 155 feet at the center of the main suspension span and 135 feet at the boundaries of the 3,000 ft. navigation channel.
People first suggested building a bridge across the Straits of Mackinac during the early 1880s. The dedication of the Brooklyn Bridge in 1883 gave Mackinac Bridge backers encouragement. On July 1, 1888, a group met at the famous Grand Hotel on Mackinac Island. The minutes show that Cornelius Vanderbilt said: "We now have the largest, well-equipped hotel of its kind in the world for a short season business. Now what we need is a bridge across the Straits."
In 1923 the Legislature ordered the State Highway Department to establish a ferry service at the Straits. Within five years traffic on this facility became so heavy that the late Governor Fred Green ordered the same agency to make a study of bridge feasibility. The report was favorable and its cost was estimated at 30 million dollars. Some strides to get the project underway were taken but it was eventually dropped.
In the extra session of 1934 the Michigan Legislature created the Mackinac Straits Bridge Authority and empowered it to investigate the feasibility of constructing a bridge and to finance the work by issuance of revenue bonds. The Authority began its studies in May 1934. Work continued until all the pieces came together and the project was approved in 1951, but financing through the sale of bonds was not completed until 1953. The bridge was officially begun amid proper ceremonies on May 7 & 8, 1954, at St. Ignace and Mackinaw City.
There are always seagulls hanging out near the bridge. Here are some photos I took last Saturday.
Just to summarize, here are the facts from the Bridge Authority's web site:
|Total Length of Bridge (5 Miles)||26,372 Ft.||8,038 Meters|
|Total Length of Steel Superstructure||19,243 Ft.||5,865 Meters|
|Length of Suspension Bridge (including Anchorages)||8,614 Ft.||2,626 Meters|
|Total Length of North Approach||7,129 Ft.||2,173 Meters|
|Length of Main Span (between Main Towers)||3,800 Ft.||1,158 Meters|
HEIGHTS AND DEPTHS
|Height of Main Towers above Water||552 Ft||168.25 Meters|
|Maximum Depth to Rock at Midspan||Unknown||Unknown|
|Maximum Depth of Water at Midspan||295 Ft.||90 Meters|
|Maximum Depth of Tower Piers below Water||210 Ft.||64 Meters|
|Height of Roadway above Water at Midspan||199 Ft.||61 Meters|
|Underclearance at Midspan for Ships||155 Ft.||47 Meters|
|Maximum Depth of Water at Piers||142 Ft.||43 Meters|
|Maximum Depth of Piers Sunk through Overburden||105 Ft.||32 Meters|
|Total Length of Wire in Main Cables||42,000 Miles||67,592 km|
|Maximum Tension in Each Cable||16,000 Tons||14,515,995 kg|
|Number of Wires in Each Cable||12,580|
|Weight of Cables||11,840 Tons||10,741,067 kg|
|Diameter of Main Cables||24 1/2 Inches||62.23 cm|
|Diameter of Each Wire||0.196 Inches||.498 cm|
|Total Weight of Bridge||1,024,500 Tons||929,410,766 kg|
|Total Weight of Concrete||931,000 Tons||844,589 kg|
|Total Weight of Substructure||919,100 Tons||833,793,495 kg|
|Total Weight of Two Anchorages||360,380 Tons||326,931,237 kg|
|Total Weight of Two Main Piers||318,000 Tons||288,484,747 kg|
|Total Weight of Superstructure||104,400 Tons||94,710,087 kg|
|Total Weight of Structural Steel||71,300 Tons||64,682,272 kg|
|Weight of Steel in Each Main Tower||6,500 Tons||5,896,701 kg|
|Total Weight of Cable Wire||11,840 Tons||10,741,067 kg|
|Total Weight of Concrete Roadway||6,660 Tons||6,041,850 kg|
|Total Weight of Reinforcing Steel||3,700 Tons||3,356,584 kg|
RIVETS AND BOLTS
|Total Number of Steel Rivets||4,851,700|
|Total Number of Steel Bolts||1,016,600|
|Total, at the Bridge Site||3,500|
|At Quarries, Shops, Mills, etc.||7,500|
|Total Number of Engineers||350|
Vehicle Traffic Volume
Traffic 2013 Traffic 2012
Rules & Regulations
- Maximum speed limit is 45 mph.
- No U-turns.
- No stopping on the Mackinac Bridge.
- In the event of a flat tire or motor failure, please remain in your vehicle. Bridge personnel on duty will investigate and assist.
- Use four-way flashers while vehicle is disabled.
- Travel in right lane – no passing.
- 500-foot spacing – no tailgating.
- Use four-way flashers.
- Maximum speed is 20 mph.
- Rules Enforced from toll plaza to Jamet Street exit.
- Trucks with a gross load of over 40 tons must request escort prior to crossing.
- Maximum allowable vehicle weight is 72 tons.