Growing up near the horrific traffic of i35, toll roads are near and dear to my heart. For just a couple dollars I’m able to skip rush hour traffic and drive 85 mph. But I always wondered how the toll cameras knew when to toll me and how much, and how the sensed my car. Oh and incase you think that by going fast enough you can skip the toll, you can’t. Here’s a 700 hp Hennessey Corvette going 200 mph, and the toll cameras still manage to get a picture of the plate: Toll Road Corvette
Elements
- Car
- Camera
- Automated vehicle identification (AVI)
- Transaction processing
Interconnections
Since toll road systems are different from state to state, here are the basics on the the toll booth scans and charges cars. ETC starts with automated vehicle identification. Each vehicle going through the toll booth must have a tag with a RFID chip in it in place on the dashboard or window. The AVI sends out a signal looking for this chip. As a car drives through the booth a camera takes a picture of the car’s license plate to get information on the driver and car. If the AVI found a toll tag on the vehicle the charge is sent to the driver (via the information from the toll tag account). If a toll tag is not found then using the picture of the license plate a bill for the toll plus a fee for not having a tag is sent to the driver through the mail.

Control/Feedback
The main control/feed back in an electronic toll collection system is wether the car has the proper RFID chip as a toll tag. That’s the deciding factor on how much the driver/owner of the car has to pay.
Function/Purpose
The purpose of the ETC is to cause less traffic on toll roads. before these systems were put into place a car would have to stop and wait to physically pay the toll at a real booth, causing traffic and slowdowns. Since people are already paying to drive on the road, there should be no traffic. By using ETC you get rid of stopping all together, insuring less traffic.