Automatic License Plate Readers: How Do They Work?

Automatic Number Plate Recognition (ANPR) is a very accurate program which uses high-speed image recognition to record number plates of vehicles automatically. It detects characters in the images, supports illumination, and verifies sequence of characters and converts images into text. This way, it gives a set of metadata to identify images having license plates of the vehicle as well as decoded text.

Hence, ANPR is a technology which is used to find the number plate or license number of the vehicle and send the data for computer processing to interpret, store, or match the information. A lot of police departments use this technology to keep track of criminal activities and motorways to detect over-speeding by calculating average speed. There are several other ways to support the safety and security of the public and to interact with vehicle-based infrastructure and transportation. Here are some of the common examples –

  • Journey Time Analysis
  • Car Park Management
  • Traffic Control
  • Tolling
  • Weighbridges
  • Retail Park Security
  • Intelligent Transport Systems
  • Bus Lane Enforcement

Some of the arrangements of license plates generally come in font placing and sizes. These camera solutions should be efficient to deal with those differences to be powerful enough. A lot of systems suffer from international differences and a lot of programs are modified individually to each nation.

The mobile units and CCTV cameras are used in Automatic Number Plate Recognition systems which are fixed to vehicles. Infrared cameras are also used for high-quality pictures of number plates. The ANPR software runs on quality hardware and is connected to other databases or applications.

ANPR systems generally work in two simple ways –

  • It enables the complete process to be done in real-time at the site
  • Others transmit all images to remote locations from several lanes to conduct the OCR

Data recorded from number plates like date time, alphanumeric, lane identification and others can be completed in around 250 milliseconds. This information can be transmitted to a computer at a far location for further processing. In a server station, a lot of systems are used to manage heavy loads. It is vital to process the images to a remote server in these systems and it needs transmission of larger bandwidth.

Retro reflecting license plates are being used by many countries. It transmits light back to the source and improves image quality. It can be done only on automatic cameras used for license plate recognition.


  • ANPR cameras are being used to detect the average speed of the vehicle on long distances.
  • Used for traffic control systems.
  • Used to detect a driver when they go away without paying toll tax or fuel.
  • Targeted ads
  • To analyze the origin-destination, route selection, and other driver’s behaviour to process transport planning.
  • Automatic Number Plate Recognition cameras recognize users automatically on the basis of the license plate and provide complete details to them related to the items they have ordered beforehand.
  • To detect the guest vehicles for visitor management.

Bottom Line

Automatic Number Plate Recognition is, all in all, a great technology to help law enforcement ensure proper safety of citizens. It supports the security and safety of people across the world. The ANPR has been evolving constantly to improve the overall flow of traffic in real-time and keep track on the traffic.

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