Physical Security
Barriers with licence plate recognition: planning, safety and GDPR
Licence plate recognition opens the barrier without a card or remote control. What companies, property managers and hotels should consider for planning, safety and data protection.
Q-entra editorial teamPublished on 6 min read
Contents
Key takeaways
- An ANPR camera reads the licence plate, the software compares it with an authorisation list (whitelist) and opens the barrier automatically if the vehicle is authorised.
- Visitors, deliveries and plates that cannot be read always need a second way in, such as an intercom, a code or an app.
- Camera angle, mounting height and lighting determine the recognition rate; a test phase at night and in the rain is worthwhile.
- Power-operated barriers and gates need suitable safety devices such as force limitation, photocells or safety edges, based on the risk assessment and EN 12453, plus regular inspections.
- Licence plates are personal data: define the purpose, put up a sign and keep passage logs only briefly.
How licence plate recognition works at a barrier
ANPR stands for automatic number plate recognition, also known as LPR. A specialised camera captures the approaching vehicle, software reads the plate using optical character recognition (OCR), and authorised vehicles drive in without a card, remote control or ticket.
- An induction loop in the ground or the camera itself detects that a vehicle is approaching the barrier.
- The camera captures the plate, usually with infrared illumination so that it can also be read at night.
- The software reads the characters and checks them against the whitelist and the stored time profiles.
- If access is granted, the barrier controller receives the opening command and the passage is logged.
- Once the vehicle has passed, the barrier closes again.
Whitelists, blacklists and time profiles
The core of every system is the whitelist, the list of authorised plates. Each entry is linked to a person or company, the entrances it applies to and a time profile: employees may drive in on weekdays from 6 am to 8 pm, for example, and the cleaning contractor only in the evening.
A blacklist is mainly useful where visitors or short-stay parkers can also drive in. It blocks specific vehicles or alerts reception, for example after repeated unauthorised parking. Decide who may create and delete entries, and review both lists regularly.
Visitors, deliveries and exceptions
Visitors can be registered in advance with their plate and a time window, for example by reception, through a visitor portal or at hotel check-in. The authorisation then expires automatically.
Dirt, snow, plates hidden by bike racks and motorcycles without a front plate mean that not every vehicle is recognised. So always plan a second way in: a video intercom to reception, a card reader or a code.
| User group | Typical solution |
|---|---|
| Employees | Permanent authorisation with time profile, blocked when they leave |
| Residents of a housing complex | Authorisation per parking space, managed by the property manager |
| Hotel guests | Plate recorded at check-in, valid until departure |
| Visitors | Pre-registration with a time window |
| Delivery services | Intercom or code with a delivery time window |
| Emergency services | Agreed emergency opening, independent of plate recognition |
Integration with access control
Plate recognition delivers the most value when it is part of the access control system. Each person then has a single record with card, smartphone credential and plate. When someone leaves the company, you revoke all authorisations in one step, including the car park.
Simple systems store the whitelist in the camera and open the barrier via a relay contact. With several entrances, it is better for the camera to pass the plate to the access controller, for example via a Wiegand or network interface. This also enables anti-passback, which blocks a second entry without a prior exit, or counting free parking spaces.
Camera position and lighting
The recognition rate depends heavily on the installation. You need a dedicated camera with the right focal length, a short exposure time and infrared illumination. Follow the manufacturer's specifications for mounting height, distance and maximum angle to the plate.
- The smaller the horizontal and vertical angle between camera and plate, the better; a camera looking steeply down or sharply from the side reads less reliably.
- Use kerbs or road markings to guide vehicles slowly and centrally towards the barrier.
- Take low sun and headlight glare into account when aligning the camera.
- An additional overview camera records vehicle and situation in case of damage or disputes.
As with any camera, the image should cover only the entrance, not the pavement or the street, so plan ANPR and overview cameras together with the rest of the video surveillance.
Safety of powered barriers and gates
Barriers, sliding gates and roller doors move heavy parts with considerable force and can crush, shear or strike people. The European standard EN 12453, published in Austria as ÖNORM EN 12453, sets out requirements for the safety in use of power-operated doors, gates and barriers. Which safety devices are needed follows from the risk assessment of the specific installation, for example whether pedestrians also use the area and whether the system closes automatically.
- Force limitation: the drive detects resistance and stops or reverses.
- Safety edges: pressure-sensitive strips on the closing edges trigger a stop or reversal on contact.
- Photocells: if the beam is interrupted, the system does not close or opens again before contact occurs.
- Safety loop: an induction loop under the barrier boom keeps the barrier open while a vehicle is underneath.
- Warning light and emergency release: a flashing light during movement and manual opening during a power failure.
There should be a separate path for pedestrians and cyclists so that nobody has to walk under a barrier. Anyone who assembles a gate from a gate leaf and a drive is usually regarded as the manufacturer of the complete system and is responsible for the risk assessment, technical documentation, declaration of conformity and CE marking. Leave this to a specialist company.
Licence plates are personal data
A licence plate can usually be linked to a person, such as the registered keeper, so plate recognition is subject to the GDPR. Define the purpose, usually controlling access to the site, and do not use the data for other purposes such as tracking working hours. If employees' entries and exits are logged, involve the works council early; depending on the set-up, a works agreement may be required.
- A sign before the entrance naming the controller and the purpose and pointing to the full privacy information.
- Short retention periods for passage logs and images, with automatic deletion; store vehicle photos only if you really need them.
- An up-to-date whitelist: entries are deleted once the authorisation ends, for example after an employee leaves or a guest departs.
- Restricted access to logs and reports, with every access logged.
The principles are the same as for any camera and are explained in detail in our article on GDPR-compliant video surveillance. For larger or publicly accessible car parks, check whether a data protection impact assessment is needed.
Maintenance and ongoing operation
A barrier system works outdoors in heat, frost and road salt, so it needs regular maintenance. For power-operated doors and gates used as work equipment, the Austrian Work Equipment Ordinance requires a recurring inspection at least once per calendar year. For barriers, the same rhythm is advisable, combined with the manufacturer's maintenance plan.
- Test safety devices such as photocells, safety edges and force limitation, and document the result.
- Clean the camera lens and infrared illuminator, and monitor the recognition rate in the log.
- Update the firmware of cameras and controllers, and run them in their own network segment.
Q-entra plans barriers, plate recognition and access control as one system and, on request, also takes care of maintenance and updates.
