Types of ANPR camera for UK estates, business parks and BIDs
You will be offered four kinds of camera for an estate ANPR scheme. Which one you need depends on the job each position has to do.
Types of ANPR camera, by the job they do on an estate
You will be offered four kinds of camera. The useful question is not which is best, but what job each position has to do.
Where each position sits on the estate is covered in our guide to planning ANPR across an estate.
| Type | Where it goes on an estate | What it needs to read reliably | Honest limits |
|---|---|---|---|
| Dedicated ANPR camera, built only to read plates, with its own infrared light | The ways in and out, one lane each | A fixed angle, a set distance and traffic coming towards it | Sees the plate and little else, so it needs an overview camera beside it |
| CCTV camera with ANPR as a software feature | Slow, controlled spots, such as a gate or a junction where vehicles turn | Setting up for plate reading, with angle, speed and lighting under control | Weaker at night and in glare. The police standard expects less of it (see "Reading plates at night, in rain and glare" below) |
| Overview camera | Beside every plate reader | A wide view and good low-light performance | Does not read plates. Its job is context |
| Relocatable ANPR unit, solar or battery powered, sending over 4G | Temporary problem spots, such as a lay-by used for fly-tipping | Enough power through a winter night, and a mobile signal | Ask how it is powered in December and what happens to reads when the signal drops |
Your committee's technical reviewer will ask who makes the cameras and where the components come from. Whoever you shortlist, get that answer in writing.
Can we keep the cameras we already have?
Yes. Older and newer ANPR units run side by side on the Smart Place system, including the CCTV cameras with ANPR built in that many estates already own. A scheme does not have to start by replacing hardware that still works.
What it does mean is that a plate-reading position and a general surveillance position are different jobs, and should be specified separately. The Home Office says so directly: "The optimum configuration of CCTV systems differs when used for general CCTV surveillance to when operated as an ANPR reader." Its own standard expects a CCTV camera doing ANPR to capture 85% of readable plates, against 98% for a dedicated camera: roughly one vehicle in seven missed, against one in fifty.
The reason is the plate itself. Its background reflects light straight back at the camera, and the law requires that the characters do not. Under Regulation 11 of the Road Vehicles (Display of Registration Marks) Regulations 2001, the plate must not be treated so that the characters "become, or are caused to act as, retroreflective characters". So under infrared light the plate is bright and the street is dark. A camera exposed for the street is exposed wrongly for the plate, and the reverse. Shutter speed pulls the same way: fast enough to freeze a moving plate is too fast for the light a street camera works with, which is why dedicated ANPR cameras carry their own infrared lamps.
In practice, existing cameras keep doing the job they do well, and plate reading is added where it earns its place, on the ways in and out first. That is how Clacksfirst BID is bringing its existing CCTV onto one network: its existing cameras stay, and "Cameras are replaced on failure rather than as a precondition of the upgrade." Replacing as cameras fail, rather than all at once, spreads the cost across the term.
Reading plates at night, in rain and glare
No ANPR camera reads every plate. Angle, distance, speed, glare, darkness, weather and dirt all cost reads, so a single accuracy figure tells you little on its own.
The nearest public yardstick is a police one. For police cameras, the Home Office expects a dedicated ANPR camera to capture 98% of readable plates and to read 95% of those correctly. For a CCTV camera doing ANPR, the capture figure drops to 85%. Both are tested by day and by night, over at least 250 vehicles in a row.
For your technical reviewer, the National ANPR Standards for Policing and Law Enforcement require a fixed camera to "capture 98% of all VRM that meet the reflective requirements detailed within the BS AU 145 (as related to the age of the plate) and are visible to the human eye and accurately read 95% of captured VRM". VRM (vehicle registration mark) means the number plate, and BS AU 145 is the British Standard for plates. These are benchmarks for police cameras, not a measure of any estate scheme, ours included.
So when a supplier quotes a figure, ask them:
- Under what conditions was it measured: day, night, rain, low sun?
- At which position, and for traffic coming towards the camera or going away?
- Over how many vehicles?
- Who checks it again after installation, and how often?
The ICO treats this as a data protection duty as well as a performance question: "both the cameras and any algorithms you use to determine a match must be of sufficient quality to prevent any misidentification of a VRM". A misread plate that matches a watchlist sends someone after the wrong vehicle.
The ICO's ANPR guidance is under review following the Data (Use and Access) Act, so check the current version before quoting it to your board.