I have been experimenting with the ac2car slot car wiring system and I think I have REdiscovered a method by which 4 cars in a single slot may be controlled independently.
One pair of cars (A/B) with on board diodes are controlled via the normal +/- slot braid/rails/ribbons on either side of the track slot, while another pair (C/D) are controlled by one of those normal power braids (e.g. +) AND another power braid (e.g., -) located in the very bottom of the slot.
Of course, all cars are diode equipped with the C/D cars' guides modified for a central "leading" braid pickup that extends from the central front edge of the guide down to the slot bottom.
Not a very elegant idea or new idea, but an interesting way to run 4 cars independently in a single slot on AC. Add a few strategic passing slot lanes adjacent to the routed racing line lane, and there ya go. Add another main/adjacent passing slot for an additional 4 car, and 8 cars can be controlled independently or up to 7 can set up as ghost/drone/jam cars if you race alone.