Toll plazas like this one are familiar sites to millions of drivers.

Photo courtesy TransCore Inc.

You never want to be stuck on a toll road without a pocket full of change. It can be a bit nerve-racking to dig through the car seats, trying to find something to give to the toll booth attendant while drivers behind you honk and yell for you to move on. These are the kinds of situations that cause delays at toll plazas.

Today, most toll roads are equipped with an electronic toll-collection system, like E-ZPass, that detects and processes tolls electronically. E-ZPass is used by several U.S. states, but most other electronic toll systems are very similar to E-ZPass. Basically, E-ZPass uses a vehicle-mounted transponder that is activated by an antenna on a toll lane. Your account information is stored in the transponder. The antenna identifies your transponder and reads your account information. The amount of the toll is deducted and you're allowed through.

Electronic toll collection is designed to make traffic flow faster, as cars don't have to stop to make a transaction. In this edition of HowStuffWorks, you will learn how the E-ZPass system tracks vehicles and collects tolls.