Maryland's E-Z pass system uses a transponder in the car and an antennae in the toll lane. When a driver drives through the toll lane, the transponder mounted to the vehicle's windshield is read by the antennae. The appropriate E-Z Pass account is then charged the appropriate toll.
E-Z Pass is an electronic toll collection system that allows drivers to prepay tolls, eliminating the need to stop at the ticket booth. The system is made up of three components: a toll transponder, that is placed inside the vehicle, an overhead antenna that reads the transponder and collects the toll, and a video camera that catches system violators by photographing the car and license plate. Vehicles attempting to to pass through a toll booth without a transponder are classified as violators.
The E-Z Pass system electronically tracks the driver's usage and account balance. A statement is mailed or emailed on a monthly or quarterly basis that itemizes toll use and provides the account balance. Drivers can also check their balance by calling the E-Z Pass automated telephone system or by checking their account online at EZPassMD.com. The account balance is replenished when it falls below a set threshold, using a credit card in an amount calculated to be equal to one month of average use, based on the past 60 days.