Given the potential economic, psychological, and human consequences of such attacks, it seems terrorists would attack US bridges and tunnels regularly. After all, terrorists have attacked such critical infrastructure in other countries; why not in the United States? Shockingly, while there has been some discussion of the risk of such attacks, there is a lack of research addressing why they have not happened. Using foiled plots as case studies, I present several major explanations as to why these plots fail—and, more importantly, what deters terrorists from pursuing them. These include counter-terrorism measures, perceived structural soundness and target hardness, expense, and terrorist preference for high body counts.