Spanning the two Michigan peninsulas is the Mackinac Bridge, the longest suspension bridge in the western hemisphere . It is always a highlight of our trips to the Upper Peninsula. When you say “Big Mac” to a Michigander, the bridge is what they think of, not the hamburger.
Counting the approaches, the bridge is five miles long.
What makes it so interesting is the very nature of its construction. A suspension bridge is designed to move to accommodate wind.
And high above the Straits of Mackinac, where Lake Michigan merges with Lake Huron at the very tip of the Michigan mitt, there is always wind.
In fact, according to the Mackinac Bridge Authority, the state agency that runs the bridge, it is possible that the deck at center span could move as much as 35 feet (east or west) due to high winds.
This would only happen under severe wind conditions, mind you. And the deck would not swing or “sway” but rather move slowly in one direction based on the force and direction of the wind. After the wind subsides, the weight of the vehicles crossing would slowly move it back into center position.
Sometimes, the bridge is shut down. Electronic signs along I-75 so alert drivers and a low power radio station continuously broadcasts bridge conditions. Large trucks usually require an escort.
But RVs usually have no problems.
I say usually. I’ve crossed the bridge in our Roadtrek a dozen times. On a couple of occasions, I was aware of some pretty stiff cross winds. Nothing that caused any serious apprehension, but enough to keep my speed down.
Occasionally, there have been vehicles rolled over on the bridge because of high winds.
In 1989 a woman driving a two-year-old Yugo inexplicably stopped her super light weight vehicle on the bridge over the open steel grating on the bridge's span. A gust of wind through the grating blew her vehicle off the bridge.
That's the only death not attributed to accidents or suicides. The most recent suicide was late last year, by someone who jumped over the rail. In 1997 a man in a Ford Bronco intentionally drove off.
But such incidents are very rare.
Yet, because of the nature of suspension bridges, there's always an element of adventure in crossing the Big Mac.
The view is always spectacular.
I put together this little video during our most recent crossing. It was late on a cloudy day on mid-September.
Some 200 feet below it, ferry boats could be seen making their way back and forth to nearby Mackinac Island from Mackinaw City, the last town in the Lower Peninsula and St. Ignace, the first town in the UP.
Before the bridge was opened in 1957, automobile ferries made the crossing.
Every Labor Day, people can walk across the bridge. I've participated in a couple of bicycle rides that also cross the bridge as well. But the bridge is only open for vehicular traffic except on a very few special occasions during the year.
So driving is how most of us cross. If you haven't driven across the Big Mac bridge, put it on your bucket list.
If you want to spend the night and check out the bridge, the best place to do so is on the UP side, at Straits State Park in St. Ignace. There are spots right along the lake shore with a view like this:
If you just want to get close and take some photos or maybe have a picnic, the Fort Michilimackinac State Park on the Mackinaw City side has lots of RV parking with great bridge views like these:
Meanwhile, here’s some facts and figures on the bridge:
|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|