The optical character recognition system in roadside cameras around Stockholm is designed to read license plates in different light conditions and from various angles. If a toll payment cannot be made through a windshield RFID transponder, or if driver information is uncertain, the system compares front and back plates.
When entering or leaving the city of Stockholm, drivers pass electronic pay stations and are charged different fees, depending on the time of day. Peak hours get the highest fees.
The radio transponder gets lodged on the inside of the windshield. It sends radio signals to a pay station when a driver enters Stockholm. Tolls are withdrawn from a driver's bank account.