How Does Automatic Number Plate Recognition Work?

An ANPR camera takes an image of a vehicle number plate; the image is passed to a reader, which locates the VRM and reads the letters and characters so that they can be identified using Optical Character Recognition (OCR) software.

Automatic Number Plate Recognition is an exciting technology that can help law enforcement and other agencies track down criminals.

But how does Automatic Number Plate Recognition work and how effective is it?

An Automatic Number Plate Recognition system, or ANPR system, works by capturing images of vehicles’ license Plates using cameras mounted on vehicles or stationary positions such as traffic poles These cameras observe passing cars; each car gets scanned for its license Plate, which enables police officers or private citizens (in some cases) to pull up information about the particular vehicle’s registration details like Plate Number, vehicle make, model, colour and more with ease.

Modern ANPR technologies also provide infrared illumination capabilities which allow them to capture clear images even at night time or under low light conditions when many other CCTV surveillance tools would fail completely.

ANPR is often used for billboard analytics – Photo: Pawel Czerwinski

Captured vehicle information is stored in a database along with a GPS location and time/date stamp that can be used later to help establish where particular cars were, or how many cars were located in an area at particular times.

OCR is a challenging yet effective technology. It relies on a high-quality picture database that contains numerous images, allowing the algorithm to compare them and find a match. A top-notch program that can handle different fonts, colours, two or more rows, and blurred pictures is an excellent tool for speeding up human operators’ tasks because of the algorithm.There is a difference between photographing license Plates and recognizing them. The computer vision approach is used in-camera image analysis.

It’s a way of processing still pictures or videos and finding objects in photos or video frames based on their placement in the frame.

Computer vision technologies function on a set of predetermined regulations and can recognize patterns or identify items in an image of a car. A computer will discover two license Plates if there are several automobiles in the picture near the bottom, in the centre, and at the top.

At InData Labs, we usually utilize Python and the OpenCV library to engineer computer vision algorithms for license Plate Recognition.

Character Segmentation

The algorithm divides the license Plate into different parts. It breaks up the Number on a license Plate into letters and Numbers and segments it based on characteristics such as colour, the distance between each letter, font, and more.


At this point, the picture has been translated into alphanumeric text. The algorithm’s job is to check the data against what is stored in a database, which it does by comparing the recognized Number to what was previously recorded.

Syntactical and Geometrical Analysis

Each Number or letter can be classified into a corresponding class. The complexity of the captured license Plate will depend on the criteria for setting these classes.The algorithms that, bit by excruciating bit, move a user toward the answer that may be utilized to achieve various commercial goals are known as “AI workflows.”Description: License Plate Recognition technology is an emerging field of computer vision that uses machine learning to Automatically read license Plates. License Plate Recognition Technology (LPRT) is often used by law enforcement agencies, for traffic management and in-car navigation systems. License Plate Recognition software can also be applied to video feeds in public areas with the goal of identifying vehicles involved in crime.

Photo: Lianhao-Qu

How effective the use of ANPR technology can really depend on how well it has been implemented; if deployed correctly, ALPR can provide law enforcement agencies with useful data about criminals’ whereabouts before crimes have even happened.

The ANPR technology is used by traffic authorities and law enforcement agencies to control the flow of vehicles, detect and issue tickets for violations such as speeding or not wearing a seatbelt, and identify stolen vehicles. It has been estimated that in 2009 about one-third of all police cameras in England were ANPR-equipped.

The first system for early detection was put in place on the A1 road and at the Dartford Tunnel. In 1981, an initial arrest was made as a result of a stolen vehicle being detected.However, ANPR took hold in widespread use only after new developments in less expensive and more user-friendly software were introduced during the 1990s.The collection of ANPR data for future usage (i.e., in solving then-unknown felonies) was first recorded in the early 2000s.

In 2005, the first case of ANPR being utilized to aid in a murder investigation occurred in Bradford, UK. Sharon Beshenivsky’s killers were discovered and subsequently convicted thanks to ANPR.

ANPR is used by traffic authorities for many purposes. How does Automatic Number Plate Recognition work?

For example, in the UK Highways Agency’s “Traffic Area Perimeter” project it was proposed to use ANPR systems on all motorways and other main roads throughout England as a means of monitoring average speed over long sections of road.

It has also been proposed that variable speed limits could Automatically be set up in conjunction with ANPR cameras. Other uses are checking vehicles against outstanding finance or clamping if appropriate equipment such as insurance, MOT certificates etc., are not present.

The Vehicle Inspectorate formerly made extensive use of ANPR vans at service stations on motorways across the UK, tracking down uninsured drivers from the details held on its databases via Number Plate Recognition technology; this is now done by local police forces.

ANPR systems can be used to collect traffic data for statistical analysis, performance measurement and predictive modelling – such as the percentage of vehicles that violate a speed limit or which vehicles might cause unexpected congestion on a highway.

This information can then be used to manage traffic flow and provide driver feedback via dynamic message signs, improve safety by detecting pedestrians in blind spots around buses, detect wrong-way movements at intersections (by tracking vehicles entering freeways using exit ramps) and provide alerts about emergency braking events due to traffic collisions further down the road.

The Aero Ranger system provides in-car ANPR technology for both priority alerts and survey data gathering.

AI Volume counts using ANPR by

Many cities and districts have developed traffic control systems to help monitor the movement and flow of vehicles around the road network. This had typically involved looking at historical data, estimates, observations and statistics, such as:

Car park usagePedestrian crossing usageNumber of vehicles along a roadAreas of low and high congestionFrequency, location and cause of road works

CCTV cameras can be used to help traffic control centres by giving them live data, allowing for traffic management decisions to be made in real-time. By using ANPR on this footage it is possible to monitor the travel of individual vehicles, Automatically providing information about the speed and flow of various routes.

These details can highlight problem areas as and when they occur and help the centre to make informed incident management decisions.

For their own control centres and for the public, several UK counties have collaborated with Siemens Traffic to create traffic monitoring systems.

How to avoid Automatic Number Plate Recognition?

The effectiveness of how does Automatic Number Plate Recognition work programs has been amply demonstrated. They include installing an electronic logging device on 9.5% of all vehicles in London, which resulted in a total reduction of more than 100 million vehicle kilometres travelled annually. The Mayor’s Office for Cycling’s Better Bike Scheme Programmes is designed to teach people about bike safety.The website has information about car parks and ongoing road construction. You can see pictures of special events on the website. Average point-to-point journey times can also be generated using ANPR technology to display on a variable message sign (VMS). This helps motorists plan their routes.

Trafficmaster, a company in the UK, has used a type of technology called ANPR to figure out the speed of cars on roads that are not freeways. They started doing this in 1998 and they have 4000 cameras. The firm says that only the first four Numbers on license Plates are recognized and other information is not saved.

How does Automatic Number Plate Recognition work?

A traffic survey is a method of collecting information about the speed, weight and movement of traffic. The data collected by this method can be used to predict future traffic flow in order to detect changes that may cause problems such as congestion or lack of road capacity. Traffic surveys are common in many parts of the world including countries like China, Australia and New Zealand where they have been mandated for use on roads with high-speed limits (generally 100km/h). In these cases, dedicated lanes must be monitored at least every 15 minutes during peak periods (i.e., Monday morning from 07:00–09:30; Wednesday evening from 16:00–18:30) when average speeds will often exceed 80 km/h (~50mph).

Previous surveys have also taken place in the UK, but these were limited to ‘road-rule’ enforcement cameras and so only provided information about vehicles that had been caught speeding.

Trafficmaster started using ANPR technology for traffic surveys on urban roads between 25–60km/h (~15–37mph) from 1998 onwards. This has enabled them to provide data on average speeds along particular road stretches during periods of peak congestion (e.g., 08:00 – 09:30 Monday morning), as well as providing a means of monitoring various routes throughout the dayside of the week. The speed limit is enforced with ANPR technology at most locations where they record vehicle movements which helps keep traffic moving safely and more efficiently around town.

License Plate Recognition technology is an emerging field of computer vision that uses machine learning to Automatically read license Plates. License Plate Recognition Technology (LPRT) is often used by law enforcement agencies, for traffic management and in-car navigation systems. License Plate Recognition software can also be applied to video feeds in public areas with the goal of identifying vehicles involved in crime.

The analytic software translates still images and videos into machine-readable characters. ML models, including those fueling license Plate Recognition technology, require huge amounts of data. ANPR Melbourne systems provide enough data from model training. And optical character Recognition (OCR) algorithms underpin custom ALPR solutions.