LPR (License Plate Recognition) is an image-processing technology used to identify vehicles by their license plates. This technology is used in various security and traffic applications, such as the access-control system featured in the following animation:

In the above example: while the vehicle approaches the gate, the LPR unit automatically "reads" the license plate registration number, compares to a predefined list and opens the gate if there is a match.

The system uses illumination (such as Infra-red) and a camera to take the image of the front or rear of the vehicle, then an image-processing software analyzes the images and extracts the plate information. This data is used for enforcement, data collection, and (as in the access-control system featured above) can be used to open a gate if the car is authorized or keep a time record on the entry or exit for automatic payment calculations.

The LPR system significant advantage is that the system can keep an image record of the vehicle which is useful in order to fight crime and fraud ("an image is worth a thousand words"). An additional camera can focus on the driver face and save the image for security reasons. Additionally, this technology does not need any installation per car (such as in all the other technologies that require a transmitter added on each car or carried by the driver).