"We introduce a simulation model to evaluate the disruptions, delays, and incremental costs inflicted on the U.S. West Coast container shipping industry by a Transportation Security Incident (TSI). Each year, more than 6,000 container ships call upon West Coast seaports handling in excess of 18.3 million containers. Current national directives do not specify uniform standards for measuring the amount of seaport cargo-handling capacity, nor decision rules to divert cargo to alternate facilities when a primary destination is degraded or unusable. Through analysis, we identify infrastructure components that are potential bottlenecks and/or vulnerable to a TSI that can potentially threaten the U.S. maritime shipping capacity. For example, we demonstrate a 10-day labor union dispute and longshoremen work stoppage that paralyzes the entire U.S. West Coast. The incident induces significant port congestion from Puget Sound to San Pedro Bay, reducing the annual West Coast vessel and import container throughput by 3 percent (174 vessels and 237,088 containers), and increases the incremental costs suffered by ocean carriers by $400 million. Additional analysis identifies opportunities for commercial and government investment in additional seaport infrastructure to alleviate West Coast port congestion, while ensuring the unimpeded continuity of operations of West Coast shipping subsequent to a TSI."