What if you were to do the same, but with subterannian trains travelling in opposite directions (?) - such that the cars north are met with the subway south a

What if you were to do the same, but with subterannian trains travelling in opposite directions (?) - such that the cars north are met with the subway south and they interact for great justice? (Im serious on the idea, but I dont know the outcome?) (I am talking about huge magnets. if that wasnt clear.) (Symbiotic asymetrical train propusion through shared interior corridor walls) (easy concept... hard execution)