There is a highway near Washington DC (I-66) that has dual-rate HOV lanes like this. During peak rush hour times, the lanes are free to vehicles with 2+ people

There is a highway near Washington DC (I-66) that has dual-rate HOV lanes like this. During peak rush hour times, the lanes are free to vehicles with 2+ people, but solo drivers can also opt to pay to use them. They wanted to ensure that the HOV lanes move fast enough that the people who are carpooling will actually be rewarded for doing so. This meant that there had to be a dynamic toll for solo drivers. Imagine the outrage when on a particularly busy day, this dynamic toll exceeded $20 for a ten-mile journey. The reality is plenty of people were cheating and using the HOV lanes as solo drivers, and now the tolling mechanism means they can no longer get away with it.