What is Automated License Plate Recognition (ALPR) ?

Automated License plate recognition (ALPR), also known as Automatic Number Plate Recognition (ANPR) or License Plate Recognition (LPR), uses computer vision to instantly recognize vehicles through photographic video or images and identify the license plate data associated with the vehicles in real-time.

How does ALPR technology work?

ALPR is built on computer vision technology, a subset of artificial intelligence where computers are taught how to interpret the visual world around them.

An ALPR system combines cameras with sophisticated software to read and identify license plates at machine speed. In the case of a parking garage, the system can then grant or deny access to the vehicle based on its license plate number.

The main physical component of an ALPR system is the camera. License plate recognition cameras are often mounted on road signs, street lamps, highway overpasses, or over the entrances to parking facilities to monitor vehicles around the clock. By contrast, mobile ALPR systems use multiple cameras mounted on the tops of vehicles used in law and parking enforcement. Other common uses of ALPR include recovering stolen cars and catching speeding drivers.

Once the LPR camera captures an image of a license plate, the image is transmitted to the automated license plate recognition software for analysis and checked against a database.

The ALPR software will receive the entire image, so the first thing it needs to do is identify the license plate using computer vision. Fortunately, since license plates are fairly uniform around the world in terms of placement, this step is usually straightforward enough for a machine to understand.

License plate recognition gets a lot more complex when it comes to actually understand the license plate and matching it to an entry in a database. Depending on the lighting conditions, for example, the software might need to automatically adjust the sizing and orientation of the image to achieve a better view of the alphanumeric characters on the license plate. In the next stage, the system will use optical character recognition (OCR) to translate the license plate number into text.

Although OCR software has been around since the 70s, its application in ALPR is challenging due to the fact vehicles may be moving, lighting conditions may not be optimal, and dirt on the license plate can obscure the camera’s view. There are also the traditional challenges of OCR to overcome, such as the need to correctly distinguish between similar-looking characters like ‘O’ and ‘0’ or ‘1’ and ‘I’.

Furthermore, license plates in Canada and the US are frequently embellished with decorative elements, which can make it more difficult for the software to identify the text. The recognition of foreign license plates also presents unique challenges, since every country uses different plate styles and sizes.

Fortunately, recent advances in neural networks mean it is now possible to identify virtually every license plate correctly. ALPR systems are the product of extensive training using many thousands of previously recorded license plates. Due to the help of highly advanced machine learning algorithms, ALPR systems can become more accurate with every plate they read. It might not be possible to achieve 100% accuracy, but today’s solutions can get very close.

What are the benefits of adopting ALPR technology?

ALPR technology has been adopted in a wide range of use cases, such as law enforcement, highway tolling, and parking. In the case of parking and access control, ALPR means greater efficiency at lower costs.

Consider, for example, how parking and access control traditionally work. While the processes vary, one that everyone will be familiar with is using parking barriers, tickets, and machines. In this case, drivers need to get a ticket and remember to run it through the machine, making a payment if required, before they can use the ticket to lift the barrier. While this might sound straightforward enough, the risk of losing a ticket remains a serious problem, in which case an attendant needs to intervene. This typically means the parking facility operator needs to pay someone to be on-site at all times. Needless to say, dealing with parking tickets and machines is also a common annoyance for customers.

ALPR automates the entire process, saving time for users of parking facilities and eliminating the need to have parking attendants on-site. For example, the camera makes a record of the license plate when the driver enters the facility, and the barrier opens automatically. When the driver leaves, the system knows exactly how long the driver has been parked for, since it will recognize the license plate. The driver can then make a contactless payment and be on their way.

Another example is automatic parking access control for residential areas or commercial buildings. Instead of having to verify their identities with a key fob or ticket or by speaking to a parking attendant, the automated license plate recognition system takes care of the entire process. And, since everything works at machine speed, that process is entirely automated and seamless. Not only is this less of a burden on residents or employees – but it also eliminates much of the work involved with managing residential or commercial parking facilities. When it comes to managing larger facilities, such as multistory carparks, these benefits are simply too great to pass up.

The future of license plate recognition

From powering self-driving cars to automating traffic control and monitoring, computer vision is one of the most transformative technologies of our times. In the case of ALPR and related solutions, the continuing evolution of technology means greater accuracy and efficiency and better use of resources. In fact, ALPR is already being used to do what humans cannot, such as monitoring high-speed traffic with dozens of vehicles passing by every minute.

Learn more with Freely Parking

Freely Parking is a leading provider of cutting-edge parking technologies and services, offering scalable smart parking solutions for parking facilities of all sizes, enabling smart buildings and communities in cities across North America. We focus on developing the next generation of intelligent parking solutions using the Internet of Things (IoT), artificial intelligence (AI), cloud computing and big data. Get in touch today to find the right parking solutions for your facilities.