You know what’s funny is that, thanks to the interoperability, all of my family members have switched their toll transponders to the Illinois I-Pass because Illinois charges no monthly fees or additional surcharges and doesn’t care where you live or what state/country your car is registered. I’m sure there are other participating toll authorities with no fees, but all the places my family members live do.

So really, you only need one state to adopt your unified transit fee idea.

> I like the idea of my toll road account also being useful for public transit, if nothing else.

Halifax, NS used to have bridges where the toll transponders worked to pay for parking at the airport - super convenient. Alas, they've since removed the tolls on the bridges, so the transponders are now useless and traffic in the downtown is even worse.