During any investigation, a consideration should always be ‘was or could a vehicle have been used?’ If so, ANPR (Automatic Number Plate Recognition) technology can potentially help without any details of the vehicle(s) being known in advance.

ANPR can identify a vehicle of interest based on its number plate. However, identification should not replace other investigative enquiries and officer discretion.

ANPR automatically reads vehicle registration marks (VRMs), for comparison against database records. The police and government agencies (such as Highways England) and commercial companies, eg, garages, shopping centres and car parks, use this system. ANPR provides a tactical option to disrupt, prevent and detect criminal activity.

Basic knowledge requirements

Investigators need to understand how ANPR data can assist them. They should:

  • understand how ANPR works and its limitations
  • know how the data can be accessed and analysed to assist their particular investigation
  • understand that ANPR data (which is not part of the National ANPR Service (NAS)) may be held by a private company, commercial service or local authority, therefore investigators will need to identify and retrieve this data in a similar way to CCTV
  • know how to present ANPR material as evidence, taking into account its sensitivity, and NASPLE requirements
  • know how to use ANPR data to address investigative intelligence gaps – ANPR can be integrated with other data sources to do this.

Further information

For more information on the potential use of ANPR, practitioners should consult their local ANPR tactical adviser, or contact the NCA Major Crime Investigative Support team. See also material.

Investigators will be supported by:

  • force analysts who can exploit ANPR data using current analytical tools
  • the NAS to resource national searches for the most serious offences
  • subject matter experts who can use the NAS to exploit ANPR data.

National ANPR Service (NAS)

The NAS is a single source of national data, which has standardised functionality to support operational response, investigations and intelligence.

It records the location of the ANPR device using GPS coordinates from the camera. This is identified through the force, source ID or camera number detail, and applies to static, moveable, multi-lane, integrated CCTV, mobile ANPR or discrete cameras.

Material from other force areas

National ANPR Standards for Policing and Law Enforcement (NASPLE)

The NASPLE sets out the requirements which police and other law enforcement agencies (LEAs) must comply with to access the National ANPR Capability (NAC).

Data from the NAC cannot be used for non-LEA purposes. However, in appropriate circumstances, a camera may provide data to both the NAC and those organisations listed at Annex A of the NASPLE, for independent management.

The NASPLE has three sections.

  • Part 1: Data Standards, which define the compliance requirements for ANPR Data.
  • Part 2: Infrastructure Standards, which define the compliance requirements for ANPR infrastructure.
  • Part 3: Data Access and Management Standards, which define the access requirements for LEAs and other organisations that are associated with ANPR data for law enforcement purposes.


The NAC comprises of:

  • the NAS; and
  • the National ANPR Infrastructure (NAI) is a network of ANPR cameras, communications links, firewalls and other related supporting components (that are the responsibility of the police and LEAs) that connect to the NAS.

ANPR in investigations

ANPR provides valuable information in investigations. It can help when no specific information is known about the target vehicle(s). ANPR should always be considered where it is known or believed that a vehicle is involved in an investigation or incident.

Where there is limited information, searches can be conducted on any known or partial VRM or vehicle description details, for example, make, model, colour or tax class. These searches can be targeted at vehicles within one or more geographically defined areas during specific date and time periods.

ANPR data, when considered with other sources of information, such as 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. ANPR can also assist in both reactive and proactive investigations, to support witness and suspect strategies and to identify vehicles and potential persons of interest.

Reactive investigations

Basic searches of ANPR data can be used to help in any investigation where a vehicle is possibly involved. The data can help to:

  • locate lost or stolen vehicles
  • identify the movements of a vehicle(s) used in 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 vehicle(s) or people in a particular location during particular time periods to assist in identifying a suspect, potential victims, or potential witnesses, for example, linking crimes or identifying witnesses to an incident.

ANPR data can also be cross-referenced and integrated with data from other sources, such as mobile phone or financial data to identify vehicles, associates and other potential sources of material. Those search results can help to identify:

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


The absence of a vehicle on an ANPR system does not necessarily eliminate the possibility of a vehicle’s or indeed 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 given in an alibi. By driving a vehicle through relevant ANPR readers at similar times and conditions as detailed in 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 several ways. As the use of ANPR in investigations becomes increasingly widespread, more sophisticated criminals may also use ANPR in an attempt to create false alibis.

Proactive investigations

As well as the methods used in reactive investigations, ANPR can also support a proactive investigation. This includes:

  • researching the movements of a vehicle which may belong to or be used by a suspect
  • locating a vehicle in support of a surveillance operation
  • initiating a trigger plan or an arrest plan (arrest/stop/notify)
  • reducing disorder
  • developing intelligence about the activities and lifestyle of a subject prior to an operation.

Mobile operations

Portable ANPR systems, consisting of a laptop and an ANPR camera, can be set up by an individual user at any location within a short amount of time to support an urgent deployment or incident response. These systems can be used covertly and overtly in both rural and urban environments to monitor vehicle movements and identify target vehicles.

Mobile teams are able to use ANPR information from the strategic road network (SRN) to identify suspect vehicles that have been lost. This information can also be used to trigger further investigative actions, which means that the target does not need constant monitoring.

See also NASPLE.



  • can produce accurate geographic location data
  • is an easily searchable system
  • provides a flexible option for deploying static, moveable, multi-lane, CCTV integrated mobile ANPR or covert assets
  • can be accessed or deployed quickly
  • is a relatively low-cost system
  • can allow the investigator to monitor several vehicles at the same time.


Despite the continual development of reader technologies, non-standard number plates or deliberate countermeasures on some vehicles may reduce the effectiveness of the optical character recognition (OCR) software to read those plates. Where this occurs, ANPR controllers and/or investigators will have to verify the accuracy of reads and hits.

The value of ANPR may also be affected by:

  • the coverage of ANPR cameras in relevant geographical areas
  • the quality of the images due to:
    • poor lighting and low contrast from over exposure, sun glare, reflection, shadows or obstructing vehicles
    • speed of vehicles (blurry images)
    • vehicles obscured by high traffic volume
    • poor weather conditions
    • obscured, broken, dirty or customised number plates
    • some foreign registration plates (although this should not prevent the input of foreign vehicle details onto local force databases).

ANPR retrieval and analysis

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


ANPR systems can produce large quantities of data, and not all of this data will be relevant. Anyone commissioning a search or analysis of ANPR data should consult their ANPR team or an experienced ANPR investigator to determine the appropriate parameters for the work, and to identify the products that can be provided and how they may assist the investigation.

Structured searches using specialist software

Parameters for searches should be proportionate and justified. Searches must comply with data protection requirements and NASPLE. Focused search parameters will help to produce more accurate results relevant to the policing purpose.

Data uses

ANPR data can be used to produce a timeline of a vehicle’s movements, which can be overlayed onto a map with known data to visualise routes. In addition, locations with the most hits can be prioritised for police intervention by identifying the optimum day and time for deploying response or surveillance teams.

The following will help the user to understand the data and identify the vehicle’s movements:

  • the 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 at the camera’s location.

Structured searches using the NAS

A number of structured searches can be supported by the NAS and can assist in sifting data, especially where large volumes of data is available.

Geographical searches

The NAS can facilitate searches across a number of geographical areas. Within the system this is known as ‘cross search’.

Geographical searches produce a list of VRMs that have appeared in a particular area or areas, and within specified timeframes. Each geographical area is defined by a centre-point and a circle or oblong drawn by the user at the time the search criteria is defined. All VRMs that appear at the location(s) within the specified timeframe can be included or excluded in the result set based on defined parameters.

Real-time/retrospective searches

A real-time and retrospective search function allows vehicles travelling in convoy, with other known targets, to be detected. This is also known 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 performed within that timeframe for all the reads on the database.

Vehicle details

Searches can be undertaken on partial or full VRM, make, model, colour or tax class of a vehicle. The results will only show vehicles that match the selected criteria.

ANPR analysis

Further information

APP on 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 will then select the appropriate technique for 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 the day, or as a tactical option if a vehicle or target has been linked to an incident. Hot spots are locations with significantly higher than usual levels of crimes and/or incidents.

The environment

The environment plays an important part in crime data development. Most 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 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 data and analysing crime and disorder hot spots may help to identify key routes and significant time periods, leading to more accurate ANPR deployment. Any deployment should be consistent with NASPLE.

Subject profile analysis

ANPR data is one of many sources of information that can be used to develop a subject profile. It can be integrated with other data sources, such as crime reports, incident reports, witness testimonies, CCTV and 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 is 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 vehicle movements 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 highlight a previously unknown location of interest. However, the analyst 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 many tactical options pinpointed 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 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 of potential interest.

Determining the usual driver

A vehicle can be driven by more than one person, so 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

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

This type of search may also help to identify unknown vehicles or additional vehicles associated with the target vehicle(s). Where more than one vehicle may have been used to leave the scene of an incident, this may help to link a vehicle witnessed at the scene to that of a known associate.

Incident analysis

Further information

ACPO (2006) Murder Investigation Manual.

ANPR data can be used in serious and major investigations. For example, it can be used to refute or verify alibi statements and to locate offenders. ANPR can also 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 to measure said effectiveness.

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 following an investigation or intelligence gathering initiative is an important part of results analysis. If ANPR was not used, any missed opportunities should be identified to ensure that the lessons learned are used in future investigations.

Page last accessed 13 December 2019