Michigan officials banned most vehicle traffic during the annual Labor Day walk across the Mackinac Bridge, fearing a terrorist strike against pedestrians crossing the nearly 5-mile-long span on Interstate 75 that links the state's two peninsulas.
No known threats have been directed at the popular holiday event, which usually draws more than 40,000 participants and provides a significant end-of-summer economic boost in the tourists towns where Lakes Huron and Michigan converge, said Col. Kriste Kibbey Etue, director of the Michigan State Police.
But recent attacks in Europe and the U.S., where hundreds have been killed or injured by terrorists plowing vehicles into crowds, illustrate the vulnerability of Mackinac Bridge walkers. At its highest point, the bridge is nearly 200 feet above the swirling Straits of Mackinac.
Officials acknowledged keeping the bridge mostly clear of vehicles for 5 ½ hours would create a massive traffic tie-up but said it was a price worth paying.
"You have to weigh that temporary inconvenience against the importance of potentially saving lives," state police spokeswoman Shannon Banner said. "We would hate to have something happen and know there were measures we could have put in place to prevent it."
Labor Day is the only day of the year when people are allowed to cross on foot, a tradition dating to 1958 — the year after the bridge was opened.
Walkers begin on the north side, near a series of toll booths. They use the two lanes on the east side of the bridge, while vehicles previously have been allowed to use the two western lanes.
Now, the only vehicles allowed from 6:30 a.m. until noon will be buses hauling people from the south end of the bridge to the north side to begin the walk or reach parking areas after finishing.
Long backups were commonplace during the walk, even with some traffic flow allowed. Bringing things to a complete halt will compound the problem.
"Our board felt this choice strikes the best balance of keeping this 60-year tradition going for tens of thousands of visitors who walk the bridge each year and keeping them safe," said William Gnodtke, chairman of the Mackinac Bridge Authority.