For toll roads, some sort of in car item that will receive a short audio ad and play it. Thus using the ad money to pay my toll. I realize there are several issues immediately off the top of it, but it could be a viable alternative to having to pay tolls.
That is an interesting idea, however certain tolls (e.g. london city) have not the goal to earn money, but to keep people away. playing ads won't keep them away.