Informed Decision-Making for Critical Infrastructure Project

The Risks of Bridge Closure

Jefferson County spans much of Washington State’s scenic Olympic Peninsula, and is home to major population centers like Port Townsend, which can only be accessed by two egress routes: the Hood Canal Bridge and U.S. Highway 101. State officials proposed closing the Hood Canal Bridge for maintenance over several weekends in July and August, months that see peak traffic flow as well as heightened wildfire risk. If a wildfire prompted an evacuation while the bridge was closed, traffic from Port Townsend would be forced through Highway 101 into Olympic National Park, a potentially lethal area to travel through during a wildfire.

Ladris Analysis 

Using Ladris modeling software, Jefferson County Emergency Management was able to forecast detailed estimates of key traffic patterns in a simulated evacuation scenario showing potential effects of the proposed bridge closure. The analysis showed that many of the proposed closure dates ranked among the busiest days for bridge traffic, and with the bridge closed, the average trip time from Port Townsend to the nearest medical center would increase from 30 minutes to 2 hours. Moreover, total evacuation time would increase threefold, from 5 to 6 hours with the bridge open to 17 to 20 hours.

Critical Decision Making

State officials overturned the decision to close the Hood Canal Bridge during the dates originally proposed for maintenance. Informed by the expertise of the Jefferson County Emergency Management team, Ladris’ evacuation modeling program produced real world metrics that supported the state’s critical decision to mitigate the risks of unsafe evacuation routes caused by a bridge closure.