Heading west from MA on route 90 and rte 80 ending in SD wondering where EZ Pass stops working. Called Ez rep and was told. "It works up to the Mississippi river" what happens after the Mississippi ...
Our I-Pass from IL works on the EZ Pass system. It worked in IL, IN, OH, WV and PA. It will work in other states in the East.
Out west, we ran into tolls in California. They had a license-plate recognition system. We had about a week to log in to the web site and pay or there would be penalties. I never really researched the penalties, just paid as we went.