A network of wind speed and direction data collection equipment on the Mackinac Bridge and two nearby lighthouses helps predict high winds and protect motorists and workers on the suspension bridge from the sometimes harsh weather high above the Straits of Mackinac.

Two anemometers atop the bridge collect wind speed data and temperature data and bridge staff use handheld anemometers and thermometers to measure wind speeds and temperatures at other locations along the bridge.

The most important elements of the bridge's weather data collection system, however, are miles west of the bridge on White Shoals and St. Helena Island lighthouses. These two systems help predict weather as it approaches from the west, allowing bridge staff to prepare for high wind speeds and other severe weather before it arrives.

The St. Helena Island Lighthouse is on St. Helena Island about seven miles northwest of the Mackinac Bridge and the White Shoals Lighthouse is about two miles northwest of Waugoshance Island and about 20 miles west of Mackinaw City.

The Mackinac Bridge Authority has an agreement with the U.S. Coast Guard, which maintains the navigational aids at each lighthouse, to install and maintain the weather data collection equipment. The Bridge Authority would like to install a third remote collection location on Bois Blanc Island in the future, which would provide data from the east side of the Mackinac Bridge, said Executive Secretary Bob Sweeney.

The weather prediction system proved its worth right away, shortly after the collection site was installed at White Shoals Lighthouse in 2006, Mr. Sweeney said.

"We just saw a big wind event," he said, "that happened within a week of putting it up. All of a sudden the wind speed monitors out there on White Shoals just skyrocketed."

In response, all bridge staff working on the bridge were called in and the contractor working on the bridge was informed to take the same precautions. The 15 to 20 minutes of advance notice in this example, Mr. Sweeney said, allowed workers on the bridge to avoid extreme winds gusting up to 70 miles per hour.

"It enabled us to get a lot of equipment and people off the bridge before things started blowing around," he said.