Also, Grazr, a lot of perople want carts that move up lifts hightower-style, so only when players are moving them.
You could augument grazr's method with a trigger that changes the speed of the cart and door when players step into it or leave it, but the number of cappers would not appear on the HUD.
It MIGHT be possible to leave the trigger_capture_area enabled, to read the players and output it to the HUD, but we're now inflating the complexity again. Not to mention that matching the (IO controlled) elevator's speed with the (team_train_watcher automatically controlled) cart's speed would be fiddly.
TL

R You might be able to manually replicate the cart's movement with inputs and outputs to move the elevator alongside it.