Inspection of trailers with regard to lighting

During a trailer inspection, lighting issues can directly lead to extra work, delays and unnecessary costs. In this article, you can read about the lighting requirements that apply during inspections and how countries may differ in their approach to carrying out these inspections.

In this article, you will read:

• when a trailer is subject to inspection
• Why lighting is a key checkpoint in trailer inspections
• EU-wide requirements for approved lighting components
• which control points inspectors pay particular attention to with lighting
• What are the most common reasons for failure in trailer lighting inspections?
• Where countries may differ in inspection procedures and frequency
• What you should pay special attention to with LED lighting, cables and connectors

Why lighting is a key inspection point during trailer inspections

During technical inspections of trailers, lighting is almost always among the first components to be checked. Faulty lights, incorrectly fitted lighting or missing approvals can lead directly to the trailer being rejected. For vehicle builders, fitters and fleet managers, this means that correct mounting, reliable cabling and approved components are essential to prevent problems during inspections. Although the organisation and frequency of inspections may vary from country to country, the technical requirements for lighting remain largely the same across Europe. Lighting plays a key role in this, as it directly affects visibility, the recognisability of driving manoeuvres and, consequently, road safety.

When is a trailer subject to inspection?

The inspection requirements for trailers vary by EU country, particularly regarding the weight limit above which a periodic inspection is mandatory and the categories to which this applies. In the Netherlands, for example, an APK inspection is compulsory for trailers weighing more than 3,500 kg, whilst other countries apply a different limit or procedure. Regardless of whether a trailer is subject to periodic inspection: as soon as it is driven on public roads, its lighting must, in any case, comply with the legal requirements. This article does not cover the broader inspection of, for example, brakes, tyres or chassis, but focuses exclusively on the lighting system.

EU-wide requirements for lighting components in testing

In all EU countries, mandatory lighting on a trailer must comply with technical requirements for visibility, recognisability and road safety. In practical terms, this means:

• All mandatory light functions must function reliably
• mounting, visibility and positioning must be correct
• Colour and function must comply with regulations
• the lighting components used must have valid approval

These requirements form the technical foundation applied throughout the EU. Whilst the way in which countries organise inspections may vary, the basic requirements for lighting remain largely the same. In our article on the rules and legislation concerning trailer lighting, you can read more about which light functions are mandatory for each type of trailer.

Semi-Trailer category	General points of attention lighting	Practical points of attention in the workshop
Trailercategory O1	General lighting considerations: Basic lighting such as rear lights, brake lights, indicators and licence plate lights	Practical points to note in the workshop: Checking for correct operation, correct mounting and the presence of approved components
Trailercategory O2	General lighting considerations: Additional functions such as rear fog lights and, depending on size, extra marker or side marker lights	Practical points to note in the workshop: Reliable cabling, correct plug configuration and waterproof connections
Trailercategory O3/O4	General lighting considerations: More extensivelighting, such as side marker lights, side marker lights and correct positioning along the length of the vehicle	Practical considerations in the workshop: Robust LED lighting and durable cabling for intensive and professional use

For an overview of approved products, you can also view our range of trailer lighting.

Why are approved lighting components important in inspections?

For legally required light functions, the lights used must comply with international vehicle regulations. In practice, you can recognise this by the E-marking for vehicle lighting on the light or lens. This marking indicates that the component has been approved in accordance with UNECE regulations for vehicle lighting, for example regarding light output, colour and electromagnetic compatibility.

During a technical inspection, inspectors therefore check not only whether the lighting is working correctly, but also whether the components used are actually approved. If a valid E-mark is missing, this may result in the trailer being rejected during inspections or periodic tests. Find out more in the comprehensive guide for professionals.

What checkpoints inspectors pay attention to with lighting

Lighting is directly linked to road safety. Therefore, this component is assessed in almost every inspection or check. In practice, defective or incorrectly fitted lights are among the most common reasons for rejection during semi-trailer inspections. Inspectors pay attention to, among other things:

• Operation of all light functions
• presence and condition of retroreflectors
• Correct mounting and alignment according to ECE R48
• correct colour and beam pattern
• presence of approved components
• State of cables, connectors and connections

Checkpoint at inspection	What we pay attention to	Why this is important	Practical tip
Inspection checkpoints: Functioningof light functions	What to look out for: Rear lights, brake lights, indicators, fog lights and licence plate lights must function correctly	Why this is important: Otherroad users must be able to see the vehicle clearly and recognise its movements	Practical tip: Truckall light functions before the inspection
Inspection checkpoints:Reflectors	What is checked: The presence, colour and condition of the mandatory retroreflectors at the front, sides and rear	Why this is important: Reflectors ensure the trailer remains visible, even in the event of a faulty light or power failure	Practical tip: Checkfor damage, dirt and missing components
Inspection checkpoints: Fittingand positioning	What to look out for: Lighting must be correctly fitted in accordance with the installation instructions	Why this is important: Incorrect position can reduce visibility and lead to the vehicle failing its inspection	Practical tip: Check the mounting height, spacing and symmetry
Inspection checkpoints: Colourand function	What to look out for: Thecorrect colour must correspond to the correct light function	Why this is important: Unusualcolours or functions can cause confusion on the road	Practical tip: Only use approved lights for the correct application
Inspection checkpoints |Approval	What to look out for: Lightingmust bear a valid E-mark	Why this is important:This demonstrates that the component has been approved in accordance with international vehicle regulations	Practical tip: Check markings during procurement and assembly
Inspection checkpoints: Cablingand connectors	What to look out for: Cables, connectors and plugs must be correctly connected and undamaged	Why this is important: Poorconnections can cause interference or lighting failures	Practical tip: Choose robust, water-resistant connections
Inspection checkpoints: Visibilityand condition of the light	What to look out for: Lamps must not be broken, loose or heavily soiled	Why this is important: Damageaffects light output and safety	Practical tip: Always include a visual inspection as part of your routine maintenance

This also applies to specialist applications, such as vehicles operating under ADR regulations. You can read more about this in ‘ADR lighting: an explanation of the regulations and practical tips’.

Common reasons for failure in trailer lighting inspections

A large proportion of lighting-related failures can be traced back to a limited number of causes. It is worth going through these points as a matter of course before every inspection:

1. A light is not working or is flashing erratically
2. A mandatory light is completely missing
3. The colour of the light does not match its intended function; for example, a white light where amber is required
4. A reflector is missing, damaged or the wrong colour
5. A light is obscured by a load, a support leg or a mounting frame
6. The mounting position does not correspond to the width or length of the trailer; for example, side marker lights that are not fitted in accordance with the installation requirements
7. Moisture, corrosion or a loose connection in the connector or plug
8. A missing or illegible E-mark on the light, or mounting that deviates from the mounting instructions

Many of these points can be identified in advance with a short visual check, even before the trailer arrives at the inspection centre.

Practical benefit: a retroreflector operates entirely without power. It cannot therefore fail due to a faulty light, a blown fuse or a loose connector, and thus keeps the trailer visible precisely when the active lighting fails.

Where can countries within the EU deviate?

Countries may differ in the organisation and execution of inspections. Examples include:

• the moment when an inspection becomes mandatory
• Inspection frequency and deadlines
• administrative requirements and documentation
• The vehicle categories that must or must not be periodically inspected

These differences do not change the basic European requirements for lighting and approved components. Those who comply with these comply with the technical foundation used in all EU countries.

Country	What can differ	What remains the same for lighting
Country: Netherlands	What may vary: Notevery trailer is subject to periodic inspection; heavier categories in particular are subject to structural inspection.	What remains the same regarding lighting: Correctoperation, mounting and approved components remain paramount
Country: Belgium	Please note: The inspection requirementand procedure may apply earlier for certain categories of trailers	Which lighting remains the same?Here too, requirements apply regarding visibility, mounting and approval of the lighting
Country: Germany	Points to note: Thefrequency of inspections and additional procedures may vary depending on the trailer class	What remains the same regarding lighting: ECE-compliantmounting and approved lighting remain the starting point

What should you pay special attention to with LED lighting, cables and connectors?

LED lighting is reliable, but requires careful attention to installation. Take particular care to ensure that components are connected correctly and are suitable for the type of trailer lighting fitted to the vehicle.

• Trouble-free operation and robust electronics
• Correct connection using suitable cables and connectors; see also our article on connecting trailer lighting
• Waterproof connections and sufficient mechanical relief
• stable operation in combination with the towing vehicle

These points are particularly relevant for intensive applications, such as international or heavy haulage. In this context, you may also wish to read more about lighting for heavy haulage.

National approval information per country

For the practical implementation of inspections and procedures we refer exclusively to official bodies. Rules may change from country to country. Therefore always consult the primary source:

• Netherlands: RDW
• Germany: Kraftfahrt-Bundesamt (KBA)
• France: Service-Public
• Italy: Ministero delle Infrastrutture e dei Trasporti
• United Kingdom: GOV.UK
• Belgium: FPS Mobility

The procedure for a trailer inspection varies from country to country. However, the technical requirements – and in particular the lighting requirements – are largely the same across Europe. By using correctly approved and properly fitted lighting, you will comply with the technical standards applied in all EU countries.

By using correctly approved lighting and ensuring careful mounting, a trailer will meet the basic technical requirements applicable throughout the EU. This reduces the risk of failure during inspections and helps you build a safe, reliable and professional lighting system for practical use.

Frequently asked questions about semi-trailer inspections and lighting

Which lighting systems are checked during a semi-trailer inspection?

An inspector checks all mandatory light functions: rear lights, brake lights, indicators, number plate lights, rear fog lights, reflectors and, for longer trailers, side marker lights. The inspection focuses on functionality, colour, mounting position and the presence of a valid E-mark on each light unit.

Can a trailer be rejected due to a faulty marker light?

Yes. A faulty marker light is classified as mandatory lighting and is therefore taken into account during the assessment. If the light is not working, this will usually result in a failure or a recommendation for repair. You should therefore always replace faulty marker lights before the inspection, even if it is a small or less conspicuous light.

Is a valid type approval mandatory for trailer lighting?

Yes, mandatory light functions must bear a valid E-mark in accordance with the relevant UNECE regulations. If this mark is missing, that in itself may be grounds for failure, even if the light is technically in perfect working order. You should therefore check the marking at the time of purchase and mounting, not just during the inspection.

Is a side marker light permitted to flash in unison with the indicator?

For certain vehicle categories, this is permitted or even mandatory, provided it is an amber side marker light that flashes in sync with the indicator on the same side. A red rear side marker light must not flash in sync. If in doubt, please consult the specific regulations for your vehicle category.

Get started straight away with reliable trailer lighting

Are you unsure whether your current lighting will pass the inspection, or would you like to switch to sustainable, ECE-certified LED lighting? Contact our specialists for no-obligation advice.