Electronic toll collection in the Chicago metro area began on the morning of 18th November 1993, just over 20 years ago, on the I-355 North-South (now the Veterans Memorial Tollway) with AT/Comm protocol transponders using the I-PASS brand. It was a very fancy transponder with memory that stored transactions, a 2-tone buzzer to indicate toll paid or a violation and an LCD display to show the account balance. It was dual frequency, the incoming signal using standard North American 915MHz but the return signal generated by the transponder went back in a lower frequency.

Theory was this allowed a faster data transfer rate since there was no need to reserve separate time slots. Maine Turn pike also adopted this AT/Comm system. It worked well but then so did the E-ZPass IAG transponder-reader system. After five years it was clear the IAG protocols were spreading while AT/Comm was not.

By the fall of 1997 as the fourth anniversary of electronic tolling approached the Illinois Tollway had fewer than 40,000 AT/Comm transponders out there against over 2 million Mark IV IAG transponders in use in New York, New Jersey and Pennsylvania. Mark IV with volume sales was able to supply its at a lower price than AT/Comm.

If the Illinois Tollway wanted to be interoperable with all the tollroads to the east it had to change. The switchover of readers and swapout of transponders happened at the end of 1997. The I-PASS brand was moved from the AT/Comm transponders to Mark IV tags. TransCore did a smooth transition installing new readers and disabling the old AT/Comm dual frequency gear to a deadline. The Tollway had sent the new transponders out a couple of weeks in advance. And conducted a marketing campaign to get the transponders changed out.

Today, the Illinois Tollway operates the largest open road tolling system in the US by transaction number, with more than 2.2 million average daily toll transactions. 86 percent of all transactions are I-PASS transactions compared with about 25% in 1997.

“I-PASS has changed the way people travel throughout our region and is one of the most compelling examples of how technology and innovation can improve quality of life by helping us get from Point A to Point B more quickly, safely and conveniently. After 20 years, it’s hard to imagine traveling on major interstates like the Jane Addams or the Tri-State and having to stop to pay tolls along the way," said Illinois Tollway Executive Director Kristi Lafleur.

Compared to 36,000 AT/Comm transponders at the 4th anniversary of the system there are now 4.8 million Mark IV/now Kapsch I-PASS transponders in vehicles. The Illinois Tollway in a 20th birthday statement claims to lead the industry as the toll agency with the highest percentage of customers paying electronically.