Automatic Number Plate Recognition (ANPR) – Overview


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Technologies towards smart vehicles, smart cities, and intelligent transportation systems continue to transform many facets of human life. As a consequence, technologies such as automatic number plate recognition (ANPR) have become part of our everyday activities. Moreover, the concept of ANPR is promising to contribute towards various use cases while eliminating human intervention.

This article presents the basic concepts of automatic number plate recognition. In particular, this article covers:

  1. What is ANPR?
  2. How does it work?
  3. Benefits and use cases

What Is ANPR?

Automatic number plate recognition is a computer vision practice that allows devices to read license number plates on vehicles quickly and automatically, without any human interaction.

Hence, ANPR is used to capture and identify any number plate accurately through the use of video or photo footage from cameras.

Automatic Number Plate Recognition (ANPR) example
Example of automatic number plate recognition (ANPR) in parking lot management applications.

How Does ANPR Work?

ANPR is one of the most accurate applications of computer vision systems. Systems for automated number plate recognition use optical character recognition (OCR) to read vehicle registration plates. Cameras capture high-speed images of number plates, and software for image processing is used to detect characters, verify the sequence of those characters, and convert the number plate image to text.

Typical ANPR systems include a digital image capture unit (camera), a processing unit, and different algorithms for video analytics. In addition, the use of infrared lighting allows such systems to capture vehicle registration plates at night, making it possible to operate ANPR at all hours of the day.

  1. Firstly, the ANPR camera captures images that contain a license plate (video stream or photo).
  2. Then, the plate is detected using machine learning and computer vision processes (Object Detection)
  3. Finally, OCR software is applied to the detected plate area to return the license plate number in text format. The converted number is usually stored in a database for integration with other IT systems.
Automatic Number-plate recognition ANPR
Automatic Number-plate recognition (ANPR) with detected plates and applied Optical Character Recognition (OCR) – Source

Benefits of Automatic Number Plate Recognition

ANPR offers numerous advantages that are the basis for real-world applications. Most benefits of ANPR come with automating manual tasks, highly efficient space management, governance, and increasing the customer experience.

  • Automation: The automated recognition of number plates allows automated alerts and controls for facilities. Hence, ANPR is a key technology for smart cities.
  • Analytics: The generated data can be used for traffic flow analytics. This is particularly important for operating intelligent transportation systems (ITS), where data processing technologies are used to improve the mobility of people and goods, demand management, increase safety, reduce traffic congestion and manage incidents effectively.
  • Identification: Fast recognition of a vehicle numberplate is the basis for fast and seamless vehicle identification. The identification can be used to grant vehicles access or find and track specific vehicles.
  • Efficiency: The precise and fast number plate recognition doesn’t rely on human input. Hence it drives cost-efficient governance and reduces waiting times.
  • Convenience: ANPR is usually integrated with other IT systems and operates in an ecosystem to provide a seamless and hassle-free experience to the end-users. Hence, the technology is used to enhance the customer experience and offer new services and products, such as automated parking payments.

Popular Use Cases of ANPR

Automatic number plate recognition is essential for a wide range of applications, where the detection, identification, or localization of vehicles is important. Read our extensive article about other use cases of computer vision in smart city applications.

Law enforcement. Police forces use ANPR for law enforcement purposes, including to check if a vehicle is registered or to identify vehicles related to traffic violations. The ability to detect and recognize number plates in real-time allows authorities to identify vehicles and track their location.

Car parking management. Car parking management requires an integrated solution to detect individual vehicles. Hence, automated number plate recognition is the key to efficient car parking management. ANPR allows parking garages to have automated parking management because every car is accounted for by its license plate number. Therefore, parking garage users avoid the stress of managing their own tickets and tracking time spent, risking penalties for inaccurate ticket payments or losing their tickets. In addition, such automated surveillance can be referred back to in case of a disagreement. Such parking systems keep track of every vehicle in the facility and ensure complete governance.

Journey time analysis. Journey time analysis (JTA) is a crucial application for authorities to identify passing through vehicles and their time from one node to another. In addition, such analytics allow better route planning for traffic administrators.

Traffic management. Traffic management is the umbrella term for a plethora of advantages that ANPR offers. ANPR can be used throughout cities to detect overspeeding vehicles, vehicles that drive rashly, or any accidental occurrence. ANPR provides solutions for measuring and analyzing area-related traffic data of a certain area or an entire city. On a larger scale, traffic management allows insights into traffic congestion for better traffic planning.

Retail park security. Retail parks often deal with unauthorized parking, leading to hassles for rightful parking spaces or sometimes suspicious activities. Such security risks can be addressed with ANPR technology by ensuring only the authorized vehicles are using parking spaces.

Tollbooth records. Manual tollbooth management on highways is still a significant practice in some parts of the world. Often, tollbooths leverage different technologies for autonomous tollbooth management. For example, on larger freeways, ANPR allows authorities to receive license plate numbers for paying tolls by mail or automatically rather than stopping and paying at a manually-run tollbooth. Hence, ANPR enables efficient toll booth management, decreasing the operational time needed and thus increasing productivity.

OCR application with a numberplate
Optical Character Recognition (OCR) application with a number plate – Source

What’s Next?

ANPR is a traditional application of computer vision and a mature technology. Hence, ANPR is broadly used in vehicle-related applications across multiple industries.

To learn more about related topics, we recommend you the following articles:

  1. The Most Valuable Computer Vision Smart City Applications (2021 Guide)
  2. Computer Vision In Manufacturing. The 10 Most Popular Applications
  3. Read an easy to understand guide about Computer Vision
  4. Learn about Object Detection with Computer Vision
  5. Explore an extensive list of Computer Vision Applications in 2021
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