Hand them the ticket and card and they sort the rest, no pin required, my visa credit and debit both work either in the manned booth or the unmanned machines.
We've always paid by card, and this facility is generally available. Am I right in thinking there are a small number of peages (the very short distance ones) that just accept coin. It's been a couple of years now, but I seem to remember paying cash somewhere between Nice and Italy - there again, I might have done this out of choice??