This technology automatically reads vehicle registration marks (VRMs), allowing these details to be compared against database records. ANPR systems are used by the police, government agencies such as Highways England, and commercial companies including garages, shopping centres and car parks. ANPR provides a tactical option to disrupt, deter and detect criminal activity, and by doing so helps to increase public confidence in the police.

Basic knowledge requirements

Those involved in investigations should understand how ANPR data can assist them. Staff need to:

  • have a basic knowledge of how ANPR works and its limitations
  • know how the data can be accessed and analysed to assist in their particular investigation
  • know the existing ANPR coverage that is relevant to their investigation (police, local authority, Highways England, commercial sources)
  • know how to present the material as evidence
  • know how to use ANPR to address intelligence gaps and assist in the reduction of crime.

The investigator will be assisted by the:

  • skills and awareness of force analysts to exploit existing ANPR data using current analytical tools
  • ability of the NADC to resource national searches for the most serious offences
  • skills and awareness of force analysts to use the NADC to exploit ANPR data.


The national ANPR data centre (NADC) allows investigators to search for matching data on a national basis (once their forces have connected their back office facility (BOF) to the NADC). The NADC records the location of the read using GPS coordinates sent via the BOF from the camera, which is identified through the force, source ID or camera number detail, irrespective of whether it is fixed, covert, overt, mobile or portable.

Material from other force areas

Where material has been sourced with assistance from another law enforcement agency (LEA) area, a memorandum of understanding (MoU) is in place between LEAs which requires that the owning LEA is consulted when preparing disclosure schedules and before material is used as evidence in criminal proceedings.

ANPR in investigations

ANPR provides valuable information which can be used in an investigation.

ANPR data, considered with other sources of information, eg, crime and incident data, intelligence, CCTV and DNA data, can provide material which supports the overall direction of an investigation or specific lines of enquiry. It can enhance the intelligence picture, identify where and when a vehicle has travelled and provide enforcement opportunities. It can also be used to assist in both reactive and proactive investigations, to support witness and suspect strategies and to identifying vehicles and, potentially, persons of interest.

Reactive investigations

Basic searches of ANPR data can be used to assist in any investigation where a vehicle is or may be involved. It can help to:

  • locate lost or stolen vehicles
  • identify the movements of a vehicle(s) used in the commission of a crime
  • research the movements of a potential suspect in order to identify the user
  • research the movements of the victim’s vehicle to assist with victimology
  • research alibis
  • identify the vehicles of people in a particular location during particular time parameters to assist in identifying a suspect, potential victim, or potential witnesses, for example, witnesses to a road traffic accident.

Search results can help to identify:

  • who was driving the vehicle and who was a passenger
  • what type of vehicle was being driven
  • when the vehicle was used
  • where the vehicle has been driven, and in which direction.

A marker against any vehicle on a database used in an ANPR operation must be supported by reliable intelligence. Investigators should remember that ANPR provides data on a vehicle’s movements, and not on an individual’s movements. It is essential that a hit on a vehicle of interest be compared with the image of the number plate and any other evidence sources, if available.


The absence of a vehicle on an ANPR system does not necessarily exclude the possibility of a vehicle’s or, by inference, a person’s presence in a particular place at a given time. In complex or serious cases, it may be appropriate to reconstruct a journey which has been given as an alibi. By driving a vehicle through relevant ANPR readers at similar times and in similar conditions to those applicable at the time of the alibi, it may be possible to determine whether the vehicle could have been at a particular location at the material time. Alternatively, it may also show that the vehicle could have passed through other locations, which may generate new lines of enquiry.

Linking an individual to a particular vehicle can be achieved in a number of ways. As the use of ANPR in investigations becomes increasingly widespread, more sophisticated criminals may also use ANPR to attempt to create false alibis.

Proactive investigations

In these cases ANPR can help to:

  • research the movements of a vehicle which may belong to or be used by a suspect
  • locate a vehicle in support of a surveillance operation
  • initiate a trigger plan or an arrest plan (arrest/stop/notify)
  • reduce disorder
  • develop intelligence about the activities and lifestyle of a subject prior to an operation.

Mobile operations

Portable ANPR systems consist of a laptop and an ANPR camera. They can be set up by an individual user at any location within a short amount of time. These systems can be used covertly and overtly in both rural and urban environments to monitor the vehicle movements of targets.

Mobile teams are able to use ANPR information from the strategic road network to identify suspect vehicles that have been lost. This information can also be used as a trigger for further investigative actions which means that the target does not need to be monitored continuously.



  • can produce accurate geographic positioning data
  • is an easily searchable system
  • provides a flexible option for deployment for fixed, temporary fixed, or mobile assets
  • can be accessed or deployed quickly
  • is relatively low cost
  • can allow the investigator to monitor a number of vehicles simultaneously.


Non-standard number plates or deliberate countermeasures on some vehicles prevent the optical character recognition (OCR) software from accurately reading those plates.  Where this occurs, ANPR controllers and/or investigators have to manually verify the accuracy of reads and hits.

The value of ANPR may also be affected by the:

  • number and type of cameras
  • location of the cameras
  • quality of the images, resulting from:
    • poor lighting and low contrast due to over exposure, sun glare, reflection or shadows  obstructed vehicles
    • speed of vehicles (blurry images)
    • traffic volume
    • poor weather conditions
    • obscured, broken, dirty or customised number plates
    • some foreign registration plates (although this should not prevent foreign vehicle details being input onto local force databases).

In addition, ANPR is limited by the level of coverage available.

ANPR retrieval and analysis

The data produced by ANPR systems can be used in intelligence processes, operational policing and investigations. It can be searched to find specific information, or analysed to identify crime trends or hot spots.


ANPR systems can produce large quantities of data, not all of which will be relevant. Any officers intending to commission a search or analysis of ANPR data should consult an experienced BOF administrator or technical adviser to determine the appropriate parameters for the work, and to identify the products that can be provided and how they may assist.

Structured searches using specialist software

Tightly focused search parameters must be defined to avoid staff being inundated. This will also help to ensure that staff are not inundated with data. This will also help to ensure that searches and analysis are meaningful. The simplest, and often most flexible, analytical approach is to export the ANPR data out of the BOF and import it into a spreadsheet or a specialist analytical software package. This should be undertaken by an experienced BOF administrator or analyst. The data can then be manipulated within the spreadsheet and extra data added to develop detail and inferences about a relevant vehicle. Data that is downloaded should be cross-referenced with the patch plate images to ensure accuracy.

Data uses

ANPR data can be used to produce a timeline of a vehicle’s movements, and can be mapped to visualise routes. In addition, locations where the most hits are seen can be prioritised for police intervention by identifying the optimum days for deploying response or surveillance teams.

The following details may help the user to understand the data and identify where the vehicle has come from and where it may be going:

  • direction in which the camera reads the VRM
  • the camera range
  • what image the camera actually captures
  • whether the camera captures the image on the entry to, or exit from, a roundabout
  • whether the camera covers all lanes and, if applicable, the hard shoulder
  • whether there are any blind spots associated with the camera location.

Structured searches using the NADC

A number of structured searches are supported by the NADC and can assist in sifting data, especially where there are large volumes of data to be collated.

Geographical searches

Geographical searches produce a list of VRMs that have appeared in a particular area, or areas, within specified timeframes. Each geographical area is defined by a centre point and a circle drawn around it using a defined radius. All VRMs that appear at a location, or locations, within the specified timeframe are included in the result set.

This search might help to identify associates of an offender, or the vehicles they are known to use. Where more than one vehicle may have been used to leave the scene of an incident, this may help to link a VRM witnessed at the scene to that of an identified associate.

Real-time/retrospective searches

The real-time and retrospective search functions allow for the detection of vehicles travelling in convoy with other known targets to be detected. This is sometimes referred to as convoy analysis. The real-time function operates on user-selected entries on a database. When a database match is generated, previous reads of the same vehicle are analysed to detect vehicles travelling together.

The retrospective function allows the user to specify a database and retrospective timeframe. The search is then be performed within that timeframe for all of the reads on the database.

Vehicle details

Where the appropriate server is available, an additional search can be undertaken on the colour, make and model of a vehicle.

Where a witness has provided details of the make, model or colour of the vehicle, ANPR can be searched using these parameters. The results show only those vehicles that match.

ANPR analysis

Any tasking of analytical resources should include discussion of the use of various sources of information, including ANPR data, although this may not be specified in the terms of reference. Analysts then select the appropriate technique to fit the task at hand.

Crime pattern analysis

When a trend, series or hot spot has been identified, ANPR data can assist either in developing a picture of vehicles in the relevant location at identified times of day, or as a tactical option if a vehicle or target has been linked to an incident. Hot spots are locations that display significantly higher than usual levels of crimes and/or incidents

The environment

This plays an important part in the development of crime, and much offending behaviour is concentrated within certain, small geographic areas. Establishing which vehicles were in the area at the time an offence or offences were committed, makes it is possible to narrow down potential suspects using additional intelligence. This can lead to the development of a trigger plan, such as an arrest plan, for the next time the vehicle travels into the defined area. By stopping that vehicle, once an ANPR camera has identified it, it may be possible to prevent a crime being committed.

Positioning ANPR cameras

Through crime pattern analysis, there is also an opportunity to identify potential future sites for both permanent and mobile ANPR cameras. Assessing road traffic collisions and analysing hot spots of crime and disorder, may help to identify key routes and significant time periods, leading to a more accurate deployment of ANPR. Any deployment should be consistent with the national ANPR standards for policing (NASP).

Subject profile analysis

ANPR data is one of many sources of information that can be used to develop a subject profile. It can be layered with other data, such as crime reports, incident reports, witness testimony, CCTV, other surveillance, communications analysis, financial analysis and existing intelligence, to define a pattern of behaviour for a subject of interest.

Profiling an individual

Once an individual can be associated with a vehicle, ANPR data can help to profile that individual. This relies on the capture and storage of historical ANPR data so that previous movements of a vehicle can be analysed. It can also identify if there is any association between the movements of the subject’s vehicle and a crime that has been committed. If a location visited by the vehicle does not form part of a pattern of normal behaviour, it may illustrate a previously unknown location of interest. The analyst, however, needs to be aware of the limitations of ANPR data and the locations of cameras in order to understand how this will influence the profile.

Building a lifestyle picture

ANPR deployment may be one of a number of tactical options identified following the identification of either a pattern of offences or a target, especially if the subject is in the early stage of development. ANPR data should be considered as a way of building up a picture of the subject’s lifestyle, before more expensive options, such as surveillance, are used.

Network analysis

Analysis of criminal groups, networks and key individuals, based on the movements of vehicles they are known to use, can help to identify networks of associates and other individuals who may be of interest.

Determining the usual driver

As a vehicle can be driven by more than one person, care should be taken to establish the identity of the driver where possible.

The usual drivers of vehicles may be verified against information obtained during a routine stop, rather than having to rely on V5 registered keeper information from the DVLA.

Convoy identification

By identifying the drivers of vehicles and their network of associates, ANPR data can be used to indicate vehicles that may be travelling in convoy. This might be used to infer that the occupants are about to make direct contact, or are about to commit an offence, or have just done so.

Incident analysis

ANPR data can be used in serious and major investigations. It can be used, for example, to refute or verify alibi statements, to locate offenders. ANPR can also be used to identify potential witnesses to specific incidents by identifying vehicles in the location at the time of an incident.

Results analysis

A review of the effectiveness of policing activity should be discussed and agreed at the start of an investigation or operation in order to set objectives against which effectiveness can be measured.

A review or results analysis is particularly useful when the response or activity is unusual, or where significant resources have been or are committed to the activity. Reviewing activity can lead to the development and improvement of practices and policy. An evaluation of the use of ANPR and its contribution is an important aspect of results analysis undertaken following an investigation or intelligence gathering initiative. If ANPR was not used, any missed opportunities should be identified to ensure that the lessons learned can be used in future investigations.

Page last accessed 19 September 2019