ANPR (automatic number-plate recognition)

ANPR is camera technology that reads vehicle number plates automatically. Cameras — often paired with infrared illumination so they work in the dark — capture an image of each passing plate, and optical character recognition converts it into text that software can check against a database in a fraction of a second.

For cities, ANPR is the quiet machinery behind congestion pricing and clean-air zones: instead of toll booths, camera rings simply record who enters and bill or fine them. London has enforced its congestion charge this way since 2003 and reused the same camera network for the 2019 Ultra Low Emission Zone, while Stockholm's congestion tax reads plates at every cordon point to charge drivers by time of day.

The catch is privacy. An ANPR network logs where and when specific vehicles travel, creating a detailed movement record that can be retained, shared or misused; misreads and dirty plates also generate wrongful fines. Most operators publish retention and accuracy rules, but the surveillance concern is real and rarely goes away.