Renee Crays hunched forward in the rear seat of her pickup. One hand clutched the headrest of the seat before her so tightly that her knuckles turned white. The Mackinac Bridge's vertical suspension cables flowed past her window as the truck climbed the gentle slope toward the center span on a recent sunny, beautiful day. Gulls soared about the bridge towers. A freighter lumbered in the distance. But Crays showed no interest in the panoramic view. She didn't glance out the side windows at all, only straight ahead, tense. "I'm scared to death of this bridge," she said. "It makes...