One pod every 1.5 seconds is the rate at the tunnel level. With multiple load/unload points (end goal, not the single point to point set up of Chicago and Dugout), the departure rate at any one node is much lower. 40 nodes would be correspond to a pod a minute entering the system. One option is a set up up similar to PCB routing. N-S at 2 tunnel diameters down, E-W at 4-5 diameters down. Then, the tricky thing is directional changes, but the elevators could also do a rotation to handle that.