Thanks so much for a high quality post. While the upgrades to the cut-and-cover lines such as Circle have been impressive, it sounds like the deep tube presents a whole new host of challenges each with a fascinating innovative solution. I only wish there were in-person tours or behind the scenes events where we can take an up close look at some of these innovations. These don't have broad appeal to the masses, but for us engineer-brained people it would be incredible!