Systems where you have to checkout are always problematic in my view. Huge queue because one terminal is broken etc. lead to maxed out fares and unhappy custome

Systems where you have to checkout are always problematic in my view. Huge queue because one terminal is broken etc. lead to maxed out fares and unhappy customers. Germany had it for a while (TouchPoint) but they gave it up thankfully — although I don't know the exact reason it was given up.