why is it so big, surely they could decrease the diameter to decrease the cost, its not like theres going to be giants roaming around the tunnel,(reply>), +Michael Flatman I wonder if they could buy TBMs much smaller.<br><br>All the tunnels I've seen smaller than this have been bored by station equipment, which requires digging holes all over (as each segment is limited by the reach of the stationary equipment).,(reply>), +CleverCrumbish oh ok,(reply>), +Michael Flatman Needs to be big enough for transport (golf cart-type stuff) for small teams of humans and their tools to access to perform maintenance. In the long run much cheaper than having to drill down the entire tunnel every time something goes wrong.