The Sainsbury's car park is a pain in the ****. The ticket machine outside so often doesn't work so then there's a bunch of faffing about to the other machine, back to the car, then on with the errand in hand.

Barriers and a pay-on-foot system? It'd get my vote.

Plan B: put a pre-pay ticket machine at the entrance, like in the Perry Vale car park, then you can pick one up as you go in.