I noticed on the website that the LIBERTE payment option is available again. This operates the same as a toll tag. Once the account is set up, and mine is linked to my Clarity card, you just swipe in and out as you go, and they invoice you at the end of the month. No need to pay in advance, and no hassle of topping up the card. A few years ago they tried to persude me to drop the option and move to prepay, saying they were stopping the option but gave up in the end. I originally changed to LIBERTE by phoning them, excellent customer service and fluent English.