Pondering about the rental car agency. It's really a tricky one. When in the passed if you didnt pay the boom would not lift - no payment no access. The driver would have to pay
But now with this system, the etag owner (or car owner) would have to pay. The rental car companies can't controll where the driver would go, meaning he could drive up and down the freeway. This is variable and risky expense.
Then, at the end of the week, the rental company would have to pay (because it's their etag and vehicle so they'll get the bill). Then they would have to charge the driver - the biggest risk of non-payment.
I would guess the best way to do it is force the driver to put a deposit down valuing the max toll amount per month, and then refund the difference back to the driver a few days later?