Seattle tried to build the largest-diameter highway tunnel ever constructed, digging through a bunch of century-old fill material used to extend the shoreline w

Seattle tried to build the largest-diameter highway tunnel ever constructed, digging through a bunch of century-old fill material used to extend the shoreline with an enormous, one-of-a-kind tunnel boring machine. The tunnel was eventually completed, after years of delay, and WSDOT is currently building out a double-decker, multi-lane highway within its shiny new monster tunnel. At the same time as this boondoggle megaproject was going on, Seattle also built five ordinary subway tunnels for its light rail network, using the same bog-standard railway-sized TBMs which have been used successfully all over the world for years, and these projects were completed on time and within budget. The premise of the Boring Company is that useful transportation infrastructure can be accomplished more cheaply by constructing even smaller, simpler tunnels with standardized tunneling machines. Their tunnels are literally just concrete tubes with concrete floors, and they are saving even more money by skipping the enormously expensive underground stations necessary with a traditional subway by using "skates" small enough to be shuttled back to the surface in an elevator. The Seattle project was enormously ambitious; the Boring Company plan is clearly designed to be as boring as possible.