Fitting instructions for dual number plate positions (O3 and O4 trailers)

In practice, we see that this leads to questions about mounting instructions, positioning and technical implementation. In particular, engineers and constructors are currently redesigning the light box or rear beam so that it meets the applicable requirements.

In this article, you will read:

• The fitting instructions for the number plate positions
• What is and what is not permitted for type approvals
• What options there are for the lighting of licence plate positions
• Explanation of the implementing regulations in force

Mounting requirements in relation to the CoC

As there is considerable interface with lighting in this issue, we at TRALERT® delved into the regulation. We translated these regulations into practice so that we can properly advise our partners (trailer manufacturers). With specific attention to situations where number plate positions and lighting touch.

We point out that when it comes to legislation, there is a chance of differences in interpretation. Therefore, it remains important that specific solutions are assessed in connection with the complete vehicle and coordinated with the competent testing authority.

What is permitted

• Two separate licence plate spaces positioned close to each other, provided that each space individually fully meets all requirements for shape, dimensions, positioning and visibility.
• Mounting on a flat or almost flat surface, which includes a grid or lattice construction, provided it is within the specified tolerances (including mesh spacing and minimum radius of curvature).
• Use of soft materials, such as foam or felt, only as vibration damping, as long as the supporting mounting surface itself consists of a constructively hard and stable material.

What is not permitted

• A mounting surface on which several licence plate positions are possible without these positions being clearly defined. And it is therefore not clear what the positions exactly are.
• Mounting where soft materials shape the load-bearing mounting surface. Soft materials must never take over the structural function of the mounting surface.
• Installation where the number plate falls outside the specified visibility zones, or is partially obscured by vehicle parts, structural elements or bodywork components.

Both licence plate positions must be separately present, independently usable and separately meet the technical requirements.

Focal points for engineering and workshop

For engineering and workshops, the dual number plate position means a change in design.

Below is a list of key considerations for modern 24V trailer lighting arising from European regulations. This table is intended as a technical reference framework for engineering and design. It sets out the explicit requirements as laid down in the applicable EU type-approval documentation. For final approval of designs, assessment of the complete vehicle, including national application and type approval, remains necessary.

Topic	Literal regulatory requirement	Source (document)
Subject: Vehicle category	Literal requirement from the regulations: Applicable to vehicles in categories O3 and O4	Source (document): Regulation (EU) 2021/535, Annex III
Subject: Number of rear number plate spaces	Literal requirement from the regulations: Vehicles in categories O3 and O4 must be fitted with two separate spaces for the mounting and securing of rear number plates	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.1.2
Subject: Purpose of the second position	Literal requirement from regulations: For the optional identification of a towing vehicle, where required by a national authority	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.1.2
Subject: Shape of mounting surface	Literal requirement from regulations: Rectangular, flat or virtually flat surface	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.1
Subject: Definition of ‘virtually flat’	Literal requirement from regulations: Surface with a radius of curvature of at least 3,000 mm	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 1.1
Subject: Grid or mesh surface	Literal requirement from regulations: Permitted provided that the mesh/bar spacing is ≤ 15 mm (mesh size or distance between bars)	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, points 1.2 and 1.3
Subject: Mounting surface dimensions	Literal regulatory requirement: Minimum dimensions 520 × 120 mm (width) or 340 × 240 mm (height)	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.2.1
Subject: Holes / cut-outs	Literal requirement from regulations: Permitted up to a maximum height of 75 mm	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.2
Subject: Protrusions	Literal regulatory requirement: Maximum 5.0 mm above the nominal surface (bolts, rivets, etc.)	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.3
Topic: Soft materials	Literal requirement from the regulations: Very soft material (foam/felt) used for vibration damping is disregarded when assessing protrusions	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.3
Subject: Width positioning	Literal regulatory requirement: Number plate must be entirely within the vehicle’s width	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.1.2
Subject: Orientation relative to the vehicle	Literal requirement from the regulations: The number plate must be perpendicular (±5°) to the vehicle’s longitudinal centreline	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.1.3
Subject: Vertical angle	Literal requirement from regulations: Permitted angles of inclination depending on mounting height	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.2
Subject: Height of lower edge (rear)	Literal regulatory requirement: At least 200 mm above the road surface	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.3.2
Subject: Height above top edge	Literal requirement from regulations: A maximum of 1,500 mm above the road surface, unless structurally impossible	Source (document): Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.3.3
Subject: Transition to new models	Literal regulatory requirement:Type approval for new vehicle types will be refused if non-compliant	Source (document): Implementing Regulation (EU) 2024/883, art. 1
Subject: Transition of existing approvals	Literal requirement from the regulations: Registration / authorisation to be put on the road will be refused from the specified date.	Source (document): Implementing Regulation (EU) 2024/883, art. 1
Subject: Number plate lighting – type	Literal regulatory requirement: Lighting must be type-approved in accordance with UN/ECE R4 or UN/ECE R148	Source (document): UN/ECE Regulation No. 4 / No. 148
Subject: Number plate lighting – installation	Literal requirement from the regulations: Installation must comply with UN/ECE Regulation No. 48	Source (document): UN/ECE Regulation No. 48

Lighting of licence plate positions

Based on the above requirements, there are various number plate and lighting solutions suitable for use within these regulations. Such as this series of number plate holders, which already incorporate lighting.

Related articles

Engineering

• Adapting CoC in case of changes to lighting
• Breaking open CoC: what does this mean for lighting?
• ECE R10: electromagnetic compatibility explained
• Lighting for heavy-duty transport
• 24V trailer lighting and cabling

Workshop

• Reduce installation time for trailer lighting
• Connecting lighting: practical challenges
• Preventing damage and interference with trailer lighting
• 24V plug & play lighting kits
• LED licence plate lights

Procurement

• Trends in trailer lighting
• Staff shortages in the bodybuilding industry
• Trail lighting: structurally reducing assembly time
• 24V truck & trailer wiring harnesses
• Connection boxes

Disclaimer

This article was compiled with great care on the basis of the currently valid European regulations and their implementing regulations. TRALERT® endeavours to keep the information as current and correct as possible. However, laws and regulations may change or be applied differently nationally, and interpretation may also differ from one type approval authority to another. The content of this article is intended as a translation of regulations into practice and cannot be regarded as legal or type-approval advice.