I know how to solve it. Install Disney like switchbacks and video monitors inside and outside every chip shop showing people queueing properly. Teenagers can't keep their eyes off a monitor, no matter what's on it.

How about the big yellow signs that say breaking in line is cause for dismissal from the shop.

or you could hold a bible with a load of book markers and wear a brightly coloured tshirt with this printed on the back...

God says "Wait your turn!" Ask me which verses.

Guaranteed they won't want to make eye contact with you. In fact they may want to stay well behind you just to avoid uncomfortable and embarrassing altercations.