You're ignoring all kinds of losses. Might as well just put an ICE on each vehicle and save effort on the whole infrastructure. There is no free energy inyour design, just wasted losses. Every step of the way. You're moving mountains to lift a marble, expecting to get enough energy back to lift another mountain. Best we can do is SAVE energy. Say, 5 cars need to get from city center to th airport. They converge, board a Boring Tunnel style skateboard that fits 5 cars back to back. Frontal area is shared, less energy expended to get them from A to B at high speed. Even better would be a one-piece cover to go overall 5 vehicles to create one smooth tight package. Obviously, when going downhill, this will be used to store energy by increasing speed (knietic energy) or so buffering through regen into a battery. Braking (turning movement into heat) should be outlawed, regenerative braking only. Seesaws don't bring any free energy, give it up. Only extreme case: a mountaintop destination where people MUST go up by car. a steep cable track could use a car coming down to largely power the other coming up. But it ony starts working when one car is already up. And when the car coming up waits for one coming down.