I have worked in the tunneling industry for nearly a decade designing, building, and procuring these jobs. Tunnels are generally the last option chosen when th

I have worked in the tunneling industry for nearly a decade designing, building, and procuring these jobs. Tunnels are generally the last option chosen when third parties are the concern. They are the most expensive option, by far, unless other factors (environmental, public impact, political perception, etc.) are considered. Therefore, once you arrive at the decision to use a tunnel, it becomes clear that third party impacts are a driver. From that point it becomes a battle of easement/property acquisition during procurement and with each easement or third party agreement comes promises that must be made to that third party. This translates into design mandates which need to be held and designed around which translates into additional design costs and then additional construction costs. If we don't hold to these agreements then litigation ensues, and so we would rather overdesign to reduce the risk profile and position the project better for the inevitable lawsuit. Other countries do not have similar litigation risks. Or at least, that's what my European contemporaries tell me when they come to work in America.