ALPR

ALPR stands for Automatic License Plate Recognition, a technology that uses cameras and optical character recognition to automatically read vehicle license plates and convert them into alphanumeric identifiers. In some regions it is referred to as ANPR (Automatic Number Plate Recognition). The technology emerged in the 1990s and became widely deployed in tolling, law enforcement, and parking management as computer vision and machine learning improved accuracy.

The workflow typically involves capturing images or video of vehicles, localizing the plate region, recognizing the characters on the plate, and matching the resulting plate number against databases. Modern systems can operate in real time, generating events that include the plate number, timestamp, and location, along with a confidence score. Readings may be processed locally or transmitted to centralized servers for aggregation and analysis.

Key components include imaging hardware (visible and sometimes infrared cameras), illumination to improve legibility, software for plate detection and OCR, and database systems for lookup, alerting, and record-keeping. Performance depends on factors such as plate design and positioning, lighting, motion blur, weather, and dirt. Variations in font, spacing, and nonstandard plates can impact accuracy, as can intentional spoofing or plate cloning.

Applications span law enforcement (tracking suspects or stolen vehicles), toll collection and congestion charging, parking enforcement, border control, and access control for facilities. Privacy, civil liberties, and data protection concerns drive governance around retention, access controls, auditing, and notification. Regulations vary by jurisdiction and may require minimization of data, limited sharing, or judicial authorization for certain uses.