UK Number Plates - Understanding BSAU145e

The number plates on your vehicle must:

• be made from a reflective material

• display black characters on a white background (front plate)

• display black characters on a yellow background (rear plate)

• not have a background pattern

• be marked to show who supplied the number plate

• be marked with a British Standard number - this is ‘BS AU 145e’ for plates fitted after 1 September 2021

The characters must not be removable or reflective. If your number plates were fitted after 1 September 2021, they must also be a single shade of black.

Your number plates can also:

• have 3D (raised) characters

• display certain flags, symbols and identifiers

• display a green flash, if you have a zero-emission vehicle

  
  

If you ride a motorbike or motor tricycle

Motorcycles and motor tricycles registered on or after 1 September 2001 must only display a number plate at the rear of the vehicle.

If you ride a motorbike or motor tricycle registered before 1 September 2001 you can also display a number plate at the front, but you do not have to.

Motorcycle and motor tricycle number plate numbers should be on 2 lines.

Towing a trailer

Your trailer must display the same number plate as the vehicle you’re towing it with. If you’re towing more than one trailer, the number plate must be fixed to the trailer at the back.

Taking commercial or heavy trailers abroad

If your trailer needs to be registered to go abroad, you need to fix the trailer registration plate to the back, as well as the towing vehicle’s number plate.

Fix the trailer registration plate as far away as possible from the towing vehicle’s number plate.

If you cannot fix the trailer registration plate on the back of your trailer, fix it to both sides instead. Make sure they’re clearly visible.

Letter spacing, size and style

The characters on a number plate need to be a certain height and size.

Our next articles will cover these

From September 2021 BSAU145e is the standard all new number plates on UK roads must be manufactured to. In other words, to be legal a number plate has to meet these rules.

A lot of the rules have been driven by ANPR cameras and law enforcement to accurately record a vehicles number plate. Many of the changes were made to make number plates more durable and visible.

Number Plate Testing

Each component of a number plate is tested to ensure they meet current standards. And only then, after they’re certified to carry the BS Number can they be sold to suppliers.

In order conform to 145e specifications, a number plate has to pass multiple tests from ensuring legibility to checking durability.

Retroreflection

A number plate background must be Retroreflective, which means it reflects light back the same way it arrived. This is an important safety feature that also increases the plates visibility. The standard states the digits and background must have different levels of retroreflection. And many different angles are checked during the test, both in wet and dry conditions.

Colourimetric

Colourimetric tests check a number plate meets the rules governing their overall colour. Because a plate background has to be white or yellow and the digits black. To do this two elements are tested, the chromaticity and luminance. Chromaticity measures the colour’s hue and saturation. And luminance measures the level of light it emits.

Bending Resistant

British number plates are resistant to bending, because they need to stay fixed on a vehicle. Notably, even on a curved surface like the rear of a vehicle. So this test checks a plate can support a 3kg weight for 2 hours or more. The standard states that if a number plate stays bent more than 25mm it fails this test.

Solvent Resistant

From car polish to washing chemicals, tar to grit salt, all sorts of chemicals can end up in contact with a plate. So this test checks to ensure they can retain their integrity even after exposure to solvents. So the plate is exposed to multiple solvents and is checked for any damage.

Weather Resistant

Being outside on a vehicle, a number plate is exposed to the weather constantly. Yet regardless of the conditions, it needs to remain legible without fading. To check a plates resistance to the weather it is exposed to over 2000 hours of UV testing. Any size of damage such as cracking, delamination or fading makes it a fail.

Corrosion Resistant

Just like solvents, number plates are tested to check their resistance to corrosion. In the long run corrosives can cause delamination, or make the registration unreadable. To test its resistance, a saline solution is sprayed onto the plate for almost 230 hours. Yet again any sign of corrosion or ingress results in a fail.

Impact Resistant

Driving on our roads exposes a number plate to endless stones, chips and minor bumps. So the BSAU145e impact test checks a plate’s durability to these constant impacts. During the test a 1kg projectile is dropped from 30-35mm onto the plate multiple times. Failure occurs if the plate delaminates, or cracks appear outside the impact site.

Thermal Resistant

Our changeable weather creates a testing environment for number plates. Thermal tests are run to simulate our climate, exposing a plate to 5 days of shifting temperatures. Any fading, blistering, cracking or delamination results in a failure.

Abrasion Resistant

This checks the plate’s resistance to abrasive particles.  To simulate road debris, a 1kg tool is rubbed across its surface for 130 minutes. Finally the plates reflectivity is checked, any reduction over 19% is a failure.

Solid Black Digits

Two tone fonts and 3D effects are no longer permitted on number plates. Only solid black digits can be used, banning 3D, Hi-Line and Carbon fonts which were previously allowed under BSAU 145d

Registration Exclusion Zone & Spacing

The space around the registration has been increased to aid readability. For this multiple rules have been set and the sizes of elements clarified. You can read about this in one of our other news articles

Fixing Rules

Number plate fixings must not obscure or alter the registration number. This is so plates are easily read. Adhesive pads are the recommended method of fixing number plates under BSAU145e.

If mechanical fixings are needed, they must not be positioned within the exclusion zone around the registration number. The four corners of the plate are the ideal position for screws or bolts.

Look out for our next news article soon.