Bridge Accident

Mackinac Bridge and Automobile Design Allegations

Mackinac, MI

Background: During a period of gusting winds, a Yugo automobile jumped the edge barrier and went over the side of the Mackinac bridge, which connects the lower and upper peninsulas of Michigan, and fell into the straits of Mackinac, killing the driver. Allegations were made that the design of the bridge and the Yugo, as well as the operating authority of the bridge, were at fault.

What We Did: Analysis, computer simulation and experiments all showed that during the accident sequence, the driver had attempted to perform a double lane change maneuver just at the moment that a gust of wind (wind speeds are continuously recorded at the bridge) synchronized with and unintentionally amplified the driver's control inputs. Using the aerodynamic properties of the car, the tire-to-bridge grate coefficient of friction value obtained via full-scale experiment with an instrumented, exemplar Yugo vehicle, simulation and expert driving by Dr. Metz, it was shown that the accident could have occurred with many other vehicles, and that the Yugo and bridge design were not at fault.

Mackinac Bridge

A fool knows the price of everything and the value of nothing.

Milton Friedman, economist/Nobel Prize winner