Mounting instructions for double registration plate position (O3 and O4 semi-trailers)

For semi-trailer manufacturers with existing type approvals, the double rear registration plate position has direct COC implications. Upon registration or commissioning, it must be demonstrated that the vehicle has two separate positions for a rear registration plate.

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:

• Mounting instructions for the licence 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 (semi-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.
• Placement where the licence plate is outside the defined visibility zones, or is partially shielded by vehicle parts, structural parts or body 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 focal points for modern 24V semi-trailer lighting arising from European regulations. This table is intended as a technical frame of reference for engineering and design. It reflects the explicit requirements as laid down in the applicable EU type-approval documentation. For final release of designs, testing against the complete vehicle, including national application and type approvals, remains necessary.

Topic	Literal regulatory requirement	Source (document)
Vehicle category	Applicable to category O3 and O4 vehicles	Regulation (EU) 2021/535, Annex III
Number of rear registration plate spaces	Category O3 and O4 vehicles must have two separate spaces for mounting and attaching rear registration plates	Regulation (EU) 2021/535, Annex III, part 2, point 2.1.2
Target second position	In view of optional identification of a towing vehicle, if required by a national authority	Regulation (EU) 2021/535, Annex III, part 2, point 2.1.2
Mounting surface shape	Rectangular flat or nearly flat surface	Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.1
Definition "almost flat"	Surface with radius of curvature of at least 3,000 mm	Regulation (EU) 2021/535, Annex III, part 2, point 1.1
Grid surface	Allowed if mesh/bar spacing ≤ 15 mm (mesh size or distance between bars)	Regulation (EU) 2021/535, Annex III, Part 2, points 1.2 and 1.3
Installation surface dimensions	Minimum 520 × 120 mm (wide) or 340 × 240 mm (high)	Regulation (EU) 2021/535, Annex III, part 2, point 2.2.1
Holes / cut-outs	Allowed up to a maximum height of 75 mm	Regulation (EU) 2021/535, Annex III, part 2, point 2.3.2
Protuberances	Maximum 5.0 mm above nominal surface (bolts, rivets, etc.)	Regulation (EU) 2021/535, Annex III, part 2, point 2.3.3
Soft materials	Very soft material (foam/felt) for vibration damping is disregarded when assessing protrusions	Regulation (EU) 2021/535, Annex III, part 2, point 2.3.3
Positioning width	Licence plate completely within vehicle width	Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.1.2
Vehicle orientation	Licence plate perpendicular (±5°) to the longitudinal median plane of the vehicle	Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.1.3
Vertical inclination	Permitted inclination angles depending on mounting height	Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.2
Bottom edge height (rear)	At least 200 mm above the road surface	Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.3.2
Top edge height	Up to 1,500 mm above the road surface, unless not structurally possible	Regulation (EU) 2021/535, Annex III, Part 2, point 2.3.4.3.3
Transition to new types	Type approvals for new vehicle types denied if not compliant	Implementing regulation (EU) 2024/883, art. 1
Transition of existing approvals	Registration / entry into service refused from set date	Implementing regulation (EU) 2024/883, art. 1
Licence plate lighting - type	Lighting must be type-approved to UN/ECE R4 or UN/ECE R148	UN/ECE Regulation No. 4 / No. 148
Licence plate lighting - installation	Installation must comply with UN/ECE Regulation No. 48	UN/ECE Regulation No. 48

Lighting of licence plate positions

Based on the above requirements, there are various licence plate and lighting solutions suitable for application within these regulations. Such as this series of licence plate holders with lighting already incorporated.

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 semi-trailer lighting and cabling

Workshop

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

Procurement

• Trends in semi-trailer lighting
• Shortage of bodybuilding professionals
• Trail lighting: structurally reducing assembly time
• truck & semi-trailer 24V 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.