ALPR vs LPR: What Is the Difference?

ALPR vs LPR is a question of language, not engineering. ALPR stands for automatic license plate recognition, the term the USA has used since the technology was developed there in the 1970s, and it is standard across Europe, Australia and much of Asia. LPR stands for license plate recognition, spelled license plate recognition in American English, and is the usual term in the United States and Canada. ALPR, automatic license plate recognition, is the same thing again, and is the term most US police forces and legislation use.

In each case a camera, usually with infrared lighting, captures the vehicle, software finds and reads the plate, and the result is checked against a list. Our ALPR explainer covers how the technology works step by step.

In the US, ALPR and LPR are used almost interchangeably. Where a difference is drawn, it is one of emphasis. LPR is the general commercial term, used by camera makers and car park operators, and is sometimes used for systems where a person checks each read. ALPR stresses the automatic, high-volume use: fixed and vehicle-mounted cameras that read every passing plate and check it against hotlists, which is why it dominates police and policy writing. A third term, LPR camera or license plate reader, often refers to the camera itself rather than the whole system.

Other names appear too. Car plate recognition (CPR) and vehicle number plate recognition are used in some markets, and some vendors simply call it plate recognition. The cameras and recognition engines behind all of them work the same way.

The real differences between systems come from plate formats rather than names. Software has to be trained for the fonts, colors and layouts used in each country, so a system sold as LPR in the US and one sold as ALPR in the USA may be tuned for different plates, even though they work the same way.

US systems usually have to identify the issuing state as well as the characters, because the same registration can exist in several states. European systems often need many national formats enabled on one site, for example at ports and border crossings.

Whatever the name, the same factors decide how well a plate-reading system performs.

Both terms cover the same three ways of deploying the cameras. Fixed systems are mounted on poles, gantries or buildings and watch one lane or entrance, which suits car parks, depots, toll points and roads. Mobile systems put cameras on a vehicle, often a police car or an enforcement van, with a rugged computer in the boot reading plates on the move and checking them against a list held on board. Handheld and portable systems, such as tripod-mounted cameras, cover short-term events and temporary sites.

Mobile reading is the hardest case: the camera and the target are both moving, the angle changes constantly and the computer has to cope with vehicle power, vibration and heat. The recognition software is the same, but the hardware has to be built for the vehicle.

The most common use on both sides of the Atlantic is parking: ticketless entry, pay-by-plate and enforcement, which our smart parking FAQ puts in context. Access control at depots and gated sites, tolling, and police hotlist checks follow close behind. The ALPR barrier control case study shows a USA deployment on compact, fanless computers in outdoor cabinets, and our PoE computers power the plate cameras from the same system that reads them.

We supply edge computers for ALPR and LPR systems as standard, configured with the operating system, camera drivers and I/O, and tested before they ship.