What I can't believe is, there are people who think paying the toll is optional while driving on a toll road.
Drive around Chicago and simply look at the top center of people's windshields. The majority of them have an I-Pass (or EZ Pass) transponder stuck up there. Like OVM said, cash customers pay twice the toll that the I-Pass/EZ Pass customers pay.
I-Pass (Illinois), I-Zoom (Indiana) and EZ Pass (NY and east coast) are all good on each other's toll roads. None of them are accepted in places like Florida, Texas, Oklahoma or Kansas.
Currently, the Indiana Toll Road and the Illinois State Toll Highway Authority have a reciprocal agreement where holders of either the i-Zoom or I-Pass receive a discount on tolls in either state, as well as E-ZPass users, and it is likewise the case between the Indiana Toll Road and Ohio Turnpike Commission. Toll discounts are currently not offered with electronic tolling on the Skyway.
Here's an interesting little known fact about the reciprocal use of I-Pass by Illinois motorists and I-Zoom by Indiana motorists on the other state's toll road...
Each state charges the other a transaction fee when the out-of-state transponder is used to pay a toll. About 70 percent of all electronic transactions on the Indiana Toll Road are done with I-PASS transponders, according to Illinois Tollway Authority figures. Until January 1, 2010, the fee was absorbed, with I-PASS users paying twice as many Indiana tolls as i-Zoom users paying Illinois tolls. In other words, people from Illinois use Indiana's tolls roads far more than the people of Indiana travel on Illinois' toll roads.
To address this imbalance, the Indiana Toll Road began charging I-PASS users a 3¢ surcharge on each of their Indiana Toll Road tolls, effective January 1, 2010.