The story of Automatic number plate recognition

Automatic number plate recognition is a mass surveillance method that uses optical character recognition on images to read vehicle registration plates.

ANPR is sometimes known by various other terms:

Automatic license-plate recognition (ALPR)
Automatic license-plate reader (ALPR)
Automatic vehicle identification (AVI)
Car plate recognition (CPR)
License-plate recognition (LPR)
Lecture automatique de plaques d'immatriculation (LAPI)
Mobile license-plate reader (MLPR)

ANPR was invented in 1976 at the Police Scientific Development Branch in the UK.Prototype systems were working by 1979, and contracts were let to produce industrial systems, first at EMI Electronics, and then at Computer Recognition Systems (CRS) in Wokingham, UK. Early trial systems were deployed on the A1 road and at the Dartford Tunnel. However it did not become widely used until new developments in cheaper and easier to use software was pioneered during the 1990s. The first arrest through detection of a stolen car was made in 1981 and the first documented case of ANPR in helping solve a murder occurred in November 2005 after the murder of Sharon Beshenivsky, in which City of Bradford based ANPR played a vital role in locating and subsequently convicting her killers.

ANPR uses optical character recognition (OCR) on images taken by cameras.

If you scan a document into your PC and then open it in a word processor you cannot edit or alter it in any way. This is because it is simply one bitmap made up of thousands of individual pixels. However there is software available, frequently a freebie with scanners that can convert these groups of pixels into characters. This is Optical Character Recognition (OCR), which scans each group of pixels and estimates whether or not it could be a letter and replaces the pixels with the ASCII* code for the letter. For instance the ASCII code for the lower case 'a' is 01100001. So, the software scans the whole document and produces a page of letters exactly the same as though you had typed them in, which can be edited or manipulated in any way.

OCR is the fundamental technology used in ANPR and provides the capability to store and sort data.

As a vehicle approaches the camera the software takes a series of 'snapshots' and stores them in a file. When the number plate is of sufficient size for the OCR software the frame is scanned and the registration number is converted to ASCII code and held in a list. This continues for a series of images according to the speed and position of the vehicle. The list is scanned for similarities and a 'favourite' selected to retain. The system would typically scan and compare 10-15 images, with 5 being considered the minimum for high accuracy. Some systems only take one image at a certain position.

Did you knew?

When Dutch vehicle registration plates switched to a different style in 2002, one of the changes made was to the font, introducing small gaps in some letters (such as P and R) to make them more distinct and therefore more legible to such systems. Some license plate arrangements use variations in font sizes and positioning—ANPR systems must be able to cope with such differences in order to be truly effective.

Australia

The New South Wales Police Force Highway Patrol were the first to trial and use a fixed ANPR camera system in Australia in 2005. In 2009 they began a roll-out of a mobile ANPR system (known officially as MANPR) with three infrared cameras fitted to its Highway Patrol fleet.The system identifies unregistered and stolen vehicles as well as disqualified or suspended drivers as well as other 'persons of interest' such as persons having outstanding warrants.

Belgium

The city of Mechelen uses an ANPR system since September 2011 to scan all cars crossing the city limits (inbound and outbound). Cars listed on 'black lists' (no insurance, stolen, etc.) generate an alarm in the dispatching room, so they can be intercepted by a patrol. As of early 2012, 1 million cars per week are automatically checked in this way.

France

180 gantries over major roads have been built throughout the country. These together with a further 250 fixed cameras is to enable a levy of an eco tax on lorries over 3.5 tonnes. The system is currently being opposed and whilst they may be collecting data on vehicles passing the cameras, no eco tax is being charged.

Germany

On 11 March 2008, the Federal Constitutional Court of Germany ruled that some areas of the laws permitting the use of automated number plate recognition systems in Germany violated the right to privacy. More specifically, the court found that the retention of any sort of information (i.e., number plate data) which was not for any pre-destined use (e.g., for use tracking suspected terrorists or for enforcement of speeding laws) was in violation of German law. These systems were provided by Jenoptik Robot GmbH, and called TraffiCapture.

United Kingdom

The UK has an extensive (ANPR) automatic number plate recognition CCTV network. Effectively, the police and security services track all car movements around the country and are able to track any car in close to real time. Vehicle movements are stored for 2 years in the National ANPR Data Center to be analyzed for intelligence and to be used as evidence.

United States

In the United States, ANPR systems are more commonly referred to as ALPR (Automatic License Plate Reader/Recognition) technology, due to differences in language (i.e., "number plates" are referred to as "license plates" in American English)

Mobile ANPR use is widespread among US law enforcement agencies at the city, county, state and federal level. According to a 2012 report by the Police Executive Research Forum, approximately 71% of all US police departments use some form of ANPR. Mobile ANPR is becoming a significant component of municipal predictive policing strategies and intelligence gathering, as well as for recovery of stolen vehicles, identification of wanted felons, and revenue collection from individuals who are delinquent on city or state taxes or fines, or monitoring for "Amber Alerts". Successfully recognized plates may be matched against databases including "wanted person", "protection order", missing person, gang member, known and suspected terrorist, supervised release, immigration violator, and National Sex Offender lists. In addition to the real-time processing of license plate numbers, ALPR systems in the US collect (and can indefinitely store) data from each license plate capture. Images, dates, times and GPS coordinates can be stockpiled and can help place a suspect at a scene, aid in witness identification, pattern recognition or the tracking of individuals.

Saudi Arabia

Vehicle registration plates in Saudi Arabia use white background, but several vehicle types may have a different background. United States diplomatic plates have the letters 'USD', which in Arabic reads 'DSU' when read from right to left in the direction of Arabic script. There are only 17 Arabic letters used on the registration plates. A Challenge for plates recognition in Saudi Arabia is the size of the digits. Some plates use both Eastern Arabic numerals and the 'Western Arabic' equivalents.

Italy

In Italian Highways has developed a monitoring system named Tutor covering more than 2500 km (2012). The Tutor system is also able to intercept cars while changing lanes.

The Netherlands

A first experimental system was tested on a short stretch of the A2 in 1997 and was deemed a big success by the police, reducing overspeeding to 0.66%, compared to 5 to 6% when regular speed cameras were used at the same location. The first permanent average speed cameras were installed on the A13 in 2002, shortly after the speed limit was reduced to 80 km/h to limit noise and air pollution in the area. In 2007, average speed cameras resulted in 1.7 million fines for overspeeding out of a total of 9.7 millions. According to the Dutch Attorney General, the average number of violation of the speed limits on motorway sections equipped with average speed cameras is between 1 and 2%, compared to 10 to 15% elsewhere.

UK

One of the most notable stretches of average speed cameras in the UK is found on the A77 road in Scotland, with 32 miles (51 km) being monitored between Glasgow and Ayr. In 2006 it was confirmed that speeding tickets could potentially be avoided from the 'SPECS' cameras by changing lanes and the RAC Foundation feared that people may play "Russian Roulette" changing from one lane to another to lessen their odds of being caught. However, in 2007 the system was upgraded for multi-lane use and in 2008 the manufacturer described the "myth" as “categorically untrue”. There exists evidence that implementation of systems such as SPECS has a considerable effect on the volume of drivers travelling at excessive speeds; on the stretch of road mentioned above (A77 Between Glasgow and Ayr) there has been noted a "huge drop" in speeding violations since the introduction of a SPECS system.

In 2015 the performance of the ANPR/LPR cameras are amazing:

From the earlyer version now the cameras were upgraded for multi-lane changes, clearerday and night capture, some cameras read fast moving up to250km/h.