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In the journey towards a safer society, technology plays a vital role in reducing crime and protecting the public. License plate readers and recognition technology represents just one of these beneficial breakthroughs from the newest video technology available. 

License plate data and recognition software and LPR, or license plate recognition for short, and LPR cameras have become far more affordable and easier to use since their inception in the 1970s. The US Bureau of Justice Statistics’ last available report found that 93% of US police departments in cities with over 1 million people operate automatic LPR systems. 

In this guide, we’ll explain the science behind modern license plate scans and discuss the many situations in which automated license plate reading and LPR technology can assist law enforcement agencies and private citizens and enhance commercial businesses and school surveillance camera systems. You’ll learn about the different LPR systems and technologies in use today and each configuration’s benefits.

License plate number detection: How does an LPR camera and scanner system work? 

In simplest terms, plate number recognition technology uses a specialized hardware camera which communicates with a connected software program to recognize and record the details found on the number plates of passing vehicles.

LPR cameras must be far more precise than the average commercial security camera, with the hardware needing to capture clear images of moving vehicles in around 20 milliseconds or less.

LPR cameras must consider several additional factors that could lead to an obscured image, such as: 

  • Resolution

  • Headlight compensation (glare reduction)

  • Dynamic range

  • Shutter speeds

While some forms of LPR (license plate recognition) technology house both LPR cameras and the optical character recognition software (OCR) used to decode the information within the same unit, these configurations are generally far less accurate than those that use two dedicated units for each task.

License plate detection and vehicle recognition: A step-by-step guide 

A commercial LPR system is generally permanent in its design, usually involving LPR cameras installed at key points throughout a parking lot, city, or property, plus software that can decipher the license plate capture. Below we’ll discuss the general workflow of a modern license plate detection program. 

Framing the license plate capture 

When a vehicle passes through an LPR camera’s field of view, the device will identify the position of the number plate in relation to the entire image. This process is commonly referred to as localization and allows the system to focus only on the license plate, ignoring any other data in the picture. 

Sizing the license plate capture 

An LPR camera may capture an image at an undesirable angle as a vehicle passes. In this case, a software algorithm will apply specialized adjustments and angular corrections to create an image that is easier for the OCR software to read. 


In some instances, shadows and shading can affect the quality of an image captured by a license plate reader camera. To account for this, various filters will be applied to read the number plate text better. Some LPR systems will even take multiple pictures in quick succession, blending them all to create a much clearer composite image for the OCR software to analyze. 

Character segmentation

In this step, the individual characters found on the license plate will be separated by the LPR system. This process involves finding the space between each letter and using this data to discern individual letters and numbers. In fixed-space fonts, this process is simple, though variable-spaced fonts can be more challenging for the software to read successfully. 

Optical character recognition (OCR)

With each character separated, the license plate reading software will be ready to produce a final image. Several OCR techniques are used in this step, including edge tracing, pattern matching and pixel repetition.

In some cases, certain characters can be hard to distinguish from each other (0’s and o’s, 1’s and I’s, etc.), and so two images may be produced to be further analyzed. 

Geometric analysis

The final step will compare the OCR-checked image(s) against the specific license plate rules for the given region, confirming that the software has been effective. This process helps to clear up any confusion between similar-looking characters and contributes to a higher confidence level in the final result. 

What to look for in an automatic LPR camera system

In the US, license plates come in various shapes and sizes. This means that an effective LPR camera must not only be capable of capturing clear images at breakneck speeds, but it must also be able to successfully differentiate between several distinct backgrounds, texts and color combinations. 

There are several ways that LPR cameras can achieve such precision. For example, wide dynamic range settings enable correct exposure across several frames; adjustable shutter speeds reduce blur in different light conditions; headlight compensation can better navigate glare when operated at night. 

Internet protocol (IP) bullet cameras are generally chosen as the most effective tools for use in an LPR system, as they’re capable of capturing high-definition images at a long range and are suitably robust for use in outdoor environments to help reduce criminal activity.

In addition, high speed cameras like a bullet LPR IP camera can communicate with connected license plate recognition software and analytics solutions, such as Alfos via a dedicated private network address, ensuring reliably fast processing times with no interference from outside sources. 

Considerations when installing a license plate recognition system

Alongside a suitable video recorder security camera capable of capturing clear images in all lighting conditions, a permanent LPR system must be designed with a few environmental factors in mind. This will ensure that the specific hardware and software combination chosen can produce usable data at a reliable rate.

The problems with infrared and night vision

In any other video security system, infrared and night vision capabilities can be beneficial for capturing footage in low-light conditions. However, these technologies can cause a few issues regarding license plate readings. 

The highly reflective paint used in license plate manufacturing will often reflect infrared light straight toward the source, resulting in an unreadable image when used as part of an LPR system. This is why many license plate recognition cameras instead use a full spectrum light source, as this produces a much less reflective ambient light that’s far less likely to affect the clarity of the final image. 

Positioning a license plate recognition camera

An LPR camera should be positioned at an angle less than 30 degrees above the intended target area to increase the chance of capturing a usable license plate image and allow varifocal lens cameras to zoom as needed. If the camera is too high, license plates can often be blocked by the bumpers and other design features found on specific models of cars and trucks. 

Additionally, it can be challenging for the human brain to distinguish characters positioned at an angle greater than 30 degrees. Even a clear image from this position may be complex for a human operator to comprehend reasonably. 

Influencing vehicle speeds

The slower a moving vehicle passes by an LPR camera, the more likely it will be that the resulting image is both clear and easily identifiable. This is due to the camera being able to considerably lower its shutter speed, keeping the shutter open for a more extended period to noticeably reduce motion blur. 

License plate scanners should ideally be installed close to a stop sign or a clearly defined junction. This way, the vehicles that pass by the camera will travel at a much more optimal speed for the LPR camera to take a clear image. 

Use cases for license plate scanner and recognition technology 

The most common application of license plate recognition technology involves monitoring vehicles in areas that regularly experience high traffic volumes; this includes commercial businesses, government buildings and public parking lots or garages. 

An automatic license plate recognition (ALPR) solution, such as Vaxtor, is ideal in these situations. Vaxtor seamlessly integrates with LPR cameras, including Pelco IP cameras for license plate recognition, to reliably utilize video streams and access control networks to capture footage in free-flow environments.

Toll collection points

Many road networks operate unmanned toll collection points, in which vehicles are expected to pay for access each time they use a particular stretch of road. Using an ALPR system here allows authorities and police officers to ensure that appropriate payments are made and assess the volume of vehicle traffic at key toll areas. 

An ALPR tollbooth also allows authorities to issue email-based invoices, meaning vehicles using the service are not required to stop each time a toll is issued. Instead, they can pay by mail at a later date. 

Law enforcement and traffic monitoring

License plate recognition technology is also frequently used by law enforcement agencies and law enforcement officers, as well as federal agencies and even homeland security across the US, proving to be a vital tool in locating and identifying criminal activity and persons of interest. 

LPR systems are ideal in areas that experience frequent traffic violations and issues with speeding. These systems can work side-by-side with traffic monitoring cameras to decrease the frequency of such offenses. They can also work to identify vehicles like stolen cars or stolen vehicles, producing real-time evidence and historical data that can be used in a criminal investigation. 

License plate recognition parking enforcement

With the assistance of an LPR, parking lot security systems can be more efficient, assisting staff to monitor large parking garages and, in turn, allowing management teams to optimize their available workforce better through automation. 

Additionally, fines and penalties for inaccurate ticket payments or overextended stays can be automatically issued from an integrated parking management system, and customer disputes can be settled fairly and reasonably with the assistance of a connected video security network. 

Unauthorized parking

Locations that often deal with unauthorized parking, such as retail parks, industrial estates and private roads, can use ALPR systems to identify offending vehicles and issue appropriate correspondence in the form of fines or written warnings. 

LPR vehicle identification solutions can also help alert authorities of suspicious activity in such locations and be integrated with additional security hardware, such as analog CCTV systems and access control networks to protect private property from potential intruders and unauthorized persons.

The benefits of license plate recognition and scanner systems

Improved security

In addition to providing authorities and private property owners with a method of identifying potential trespassers, automatic license plate recognition systems can effectively deter crime.

If an ALPR system is visible to passing vehicles, simply knowing that a recording system is in operation can be enough to dissuade criminal behavior. Law enforcement agencies can also use ALPR data to check for suspicious vehicles or search for vehicles they suspect are involved in a reported crime. 

The use of ALPR software carries benefits to lower levels of security too. For instance, if a vehicle has been previously banned from private premises, this technology can be used as an identification tool to support any further action being taken against the individual in question. 

Real-time imaging

Another great benefit of modern ALPR technology is its ability to provide real-time imaging to private security teams and other relevant authorities. In the past, license plate reading and analysis would take considerable time before producing a usable result, leading to penalty notices and fines taking far longer to be issued and eventually resolved. 

However, with ALPR technology, reading and analyzing license plate information can be carried out almost instantaneously, with the resulting data being checked against an official database to locate vehicles and vehicle owners much more efficiently. 

Journey time analysis and traffic management

License plate reader systems have quickly become a vital tool used by authorities and highway agencies to record and analyze public road systems. By setting up nodes along certain stretches of road, teams can gather valuable data concerning vehicle speeds, congestion and other important metrics. 

The data collected can be used to crack down on traffic violations, plan more effective road network infrastructure and help cities to allow for better route planning to be used by traffic administrators. 

Due to the automatic nature of this technology, installing and using such systems doesn’t significantly strain human or financial resources, freeing up departments to divert their attention to other aspects of their operations.

License plate detection and scanner limitations

As is expected with any form of technology, there are a few limitations regarding license plate recognition systems. However, for the most part, these issues can be mitigated through the deployment of a more comprehensive integrated security system. 

Additional equipment

In many cases, a license plate scanner will need to be installed alongside dedicated security cameras, such as compliant ONVIF cameras, and a centralized video recorder, as this will allow the system to send recorded data and receive necessary directives.

While a standalone LP camera system may seem like more bang for your buck, a multi-faceted integrated security system is less likely to produce a license plate reader error, and offers more advanced security features and analytics in comparison.

How far can a license plate scanner camera read?

Though the maximum effective range for a license plate recognition system will vary to some extent depending on the specific hardware used, the best LPR cameras can generally discern usable number plate data from a distance of between 50 to 100 feet.

Video quality will also factor into this equation, with most popular LPR IP dome and bullet cameras configured to record in 1080p high definition. In addition, there are some newer LPR cameras capable of recording 4K quality footage. However, these devices will require a larger hard drive or dedicated server to store the more extensive data files produced by this video quality.

Final thoughts: Is ALPR camera and scanner technology right for your business?

License plate recognition systems continue to provide several important benefits to public, private, and government agencies across the US. However, these systems are best used with related technologies and well-planned infrastructure. 

ALPR technology has been shown to aid in the automation of essential services such as parking management, traffic control and law enforcement, proving the value in the continued development of more advanced city camera systems, including working in tandem with the growing artificial intelligence and video analytics industries. LPR camera technology is a smart investment for many businesses where vehicle traffic can raise security or safety concerns, and can help streamline security operations and management when implemented using the best practices outlined in this guide.

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