Regulations for additional reversing lights, manoeuvring lights and work lights on O4 vehicles

This article covers the regulations for O4 trailers and semi-trailers with a technically permissible maximum mass exceeding 10,000 kg. We distinguish between European vehicle type-approval (WVTA) and retrofitting to existing vehicles. The focus is on additional reversing lights (AR), manoeuvring lights (ML) and work lights. For lighter trailers and semi-trailers, please refer to the regulations for additional lighting on O3 vehicles (over 3.5 tonnes up to and including 10 tonnes).

What additional lighting is permitted on an O4 semi-trailer?

The O4 category comprises heavy towed vehicles, such as curtain-sided trailers, refrigerated and frozen goods trailers, tankers, tippers, container chassis, flatbeds and heavy car transporters. It is not the body type but the technically permissible maximum mass that determines whether a vehicle belongs to category O4.

We distinguish between three light functions: additional reversing lights (AR), manoeuvring lights (ML) and work lights. The requirements for approval, number and connection vary depending on the function.

The vehicle types mentioned are examples of applications. The legal requirements apply to the relevant vehicle category and light function, not exclusively to these specific models. The applicability of specific UNECE provisions depends in part on the applicable series of amendments and the approval route.

The product name is not decisive. A manufacturer may market a light as an LED work light without it being approved as a reverse light or manoeuvring light. You should therefore check that the correct function is specified in the approval documentation and on the markings.

O3 or O4? The distinction is based on a technically permissible maximum mass of 10,000 kg: O3 is for vehicles weighing more than 3,500 kg up to and including 10,000 kg, whilst O4 is for vehicles weighing more than 10,000 kg. The numbers of AR and ML lights discussed here, within the context of the UNECE regulation cited, hang primarily from the vehicle length and not from that mass limit.

We do not cover the standard requirements for mandatory vehicle lighting here. For this, please refer to the TRALERT® overview of truck and semi-trailer lighting.

Additional reversing lights on O4 vehicles

Reversing lights illuminate the area behind the vehicle and make reversing visible to other road users.

The installation requirements are set out in UNECE R48.

How many reversing lights are permitted?

Vehicle length	Number of reverse lights
Vehicle length: Up to and including 6 metres	Number of reversing lights: 1 mandatory, a second optional
Vehicle length: Long er than 6 metres	Number of reversing lights: 2 mandatory, up to 2 additional optional

For an O4 semi-trailer longer than 6 metres, this regulation therefore stipulates two mandatory and a maximum of two additional reversing lights. The vehicle’s weight alone does not affect this maximum.

You can fit the two optional lights at the rear or, subject to certain conditions, on the sides.

Please note: the maximum of two additional lights applies to the rear and sides combined.

Fitting reverse lights at the rear

Under UNECE R48, standard reverse lights must be fitted at a height of between 250 and 1,200 mm above the road surface. There are also requirements regarding horizontal and vertical visibility and the direction in which the light is mounted.

Also check whether the surface mounting, rear bumper, tail lift and other vehicle components affect the beam pattern or the required visibility.

Additional side reverse lights

For vehicles longer than 6 metres, the two optional reverse lights may also be fitted to the sides.

Side lights provide extra visibility along the sides of the vehicle, for example when reversing into a loading bay.

When mounting lights to the side, you must take into account the applicable orientation and visibility regulations. A light approved solely for mounting directly to the right is therefore not automatically suitable for every side position.

The Dutch RDW MOT handbook also explicitly states that additional reversing lights may be fitted to the side of a trailer.

How are additional reverse lights switched on?

Reversing lights are normally switched on automatically when reverse gear is selected.

For the two optional side reversing lights, UNECE R48 also provides a specific provision for their use during slow forward manoeuvres.

Additional conditions apply, including separate control and automatic switch-off when the forward speed exceeds 10 km/h.

When retrofitting, please also check whether the national requirements for the vehicle in question permit the chosen wiring configuration.

Which lights are suitable for use as reverse lights?

The light must have a valid approval for the reversing function in accordance with ECE R23 or R148. A light used as a reverse light must be approved for the AR function.

• ECE R23: the original regulation for reverse lights and manoeuvring lights.
• ECE R148: the harmonised regulation for light-signalling devices, which includes these functions, amongst others.

When selecting products, therefore, check not only the ECE standard but also the function code, marking and technical documentation.

A general E-mark or ECE R10 approval does not automatically make a light suitable for use as a reverse light.

Manoeuvring lights on a heavy-duty O4 semi-trailer

Manoeuvring lights are designed to illuminate the area immediately adjacent to the vehicle during low-speed manoeuvres.

Since June 2023, UNECE R48 has also included this light function for trailers and semi-trailers.

How many manoeuvring lights may be added?

Length of O4 vehicle	Maximum number of manoeuvring lights
O4 vehicle length: Up to and including 6 metres	Maximum number of manoeuvring lights²: 1 per side
Length of O4 vehicle: More than 6 metres up to and including 9 metres	Maximum number of manoeuvring lights: 4, maximum 2 per side
Length of O4 vehicle: Longer than 9 metres	Maximum number of manoeuvring lights: 6, maximum 3 per side

The maximum of six applies exclusively to vehicles longer than 9 metres.

Where can manoeuvring lights be fitted?

The maximum mounting height is 1,500 mm above the road surface. There are also requirements regarding longitudinal positioning, spacing between lights and the area that must be visible from the light.

When integrating the lighting into the chassis, take the vehicle’s construction into account. For example, side guards, mudguards, axles and bodywork components must not unduly restrict the required light distribution.

What type of approval is required?

For manoeuvring lights, specific approval for the ML function in accordance with ECE R23 or R148 is required.

The function code ML indicates that the light has been approved for manoeuvring lights. The light distribution and photometric requirements differ from those for an AR reverse light.

A light with only an AR approval must therefore not be used as a manoeuvring light without further consideration. The same applies the other way round.

How should manoeuvring lights be switched on and off?

The circuitry for manoeuvring lights must also meet specific requirements.

Under the regulations for trailers, the manoeuvring lights must not be able to be switched on when the trailer’s position lights are switched off.

UNECE R48 permits automatic activation under certain conditions, for example in conjunction with the reversing function or a reversing camera system.

A key requirement is that the manoeuvring lights switch off automatically as soon as the trailer’s forward speed exceeds 15 km/h.

The trailer must provide the speed information itself. Depending on the vehicle configuration, this information can, for example, be supplied by the electronic braking system (EBS).

You should therefore decide during the design phase how the speed signal and control system will be integrated.

Simply connecting an ML light to the reversing circuit is therefore not sufficient to comply with all installation regulations.

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Lighting for semi-trailers and heavy goods vehicles

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Additional work lights for loading and unloading

However, not all additional lighting needs to fulfil an AR or ML function.

If you wish to illuminate a work area, individually switched work lights are often the best option.

This light function is used, amongst other things, for tail lifts, tool compartments, ramps and work carried out around the vehicle.

When should you opt for standard work lights?

Examples of applications include:

• Machinery transporters: lighting whilst securing machinery with lashing straps and chains.
• Tipper trailers: improved visibility of the work area during unloading.
• Car transporters: lighting around the ramps during loading.
• Enclosed and temperature-controlled trailers: lighting around the tailgate and the loading area.

How many work lights may be fitted?

For standard work lights, there is no comparable numerical limit as there is for AR and ML lights.

However, this does not mean that you are permitted to use the lights without restriction. Installation and use must comply with the relevant national regulations. Furthermore, the lighting must not pose a danger or cause a nuisance to other road users.

Where can work lights be fitted?

An underbody light can illuminate the area next to a tail lift; a higher-mounted work light typically covers a larger area.

• The light distribution and the direction of the light beam.
• Protection against moisture, dirt, stone chips and mechanical damage.
• Available space for cables and connectors.
• Mounting to the chassis or surface mounting.
• Preventing light spill that causes a nuisance to other road users.

For vehicles operating internationally, it is advisable to also take into account the regulations of the relevant countries when deciding on the fitting position.

Are work lights permitted to switch on automatically when reverse gear is engaged?

You must not use a standard work light without AR approval as a reverse light.

Would you like the lighting to switch on automatically when reversing? If so, choose a light with the correct functional approval and a circuit that complies with the relevant regulations.

For work lights that you use exclusively whilst carrying out work, a separate control unit usually offers the clearest solution.

This can be achieved, for example, using a switch on the vehicle or a separate control from the cab.

Is it permitted to have work lights on whilst driving?

The regulations vary from country to country.

In the Netherlands, work lights on trailers are permitted. However, their use must not pose a danger or cause a nuisance to other road users.

In Germany, Section 52(7) of the StVZO stipulates that work lights must not be used whilst the vehicle is in motion. Furthermore, other road users must not be dazzled.

When using the vehicle internationally, please take into account the regulations of the countries in which the vehicle is operated.

Points to consider for heavy-duty O4 semi-trailers

With O4 vehicles, it is not just the choice of light that matters, but also its integration into the often long and intensively used vehicle structure. The points to note below are practical design choices, not additional O4-specific regulatory requirements.

• Chassis and side panelling: ensure that side panelling, toolboxes or mudguards do not restrict the required light distribution of AR or ML lights.
• Moving parts: check the fitting position on sliding tarpaulin structures, tail lifts, ramps and other moving parts.
• Cabling: ensure cable routes, connectors, sealing and strain relief are designed to withstand vibrations, contamination and allow for maintenance access.
• Tractor-semi-trailer interface: assess how power and control signals are transmitted, particularly when an ML system requires speed information from the semi-trailer.
• Vehicle variants: specify for each model which light function, mounting position and electrical configuration are covered by the vehicle type-approval.

European type approval or retrofitting

Different assessment procedures apply to new vehicles with European type approval than to existing vehicles on which you are retrofitting lighting.

Route 1: new O4 trailer with European type approval (WVTA)

With a new O4 trailer, you can include the lighting in the European type approval for the entire vehicle right from the design stage.

For AR and ML lighting, it must be demonstrated, amongst other things, that:

• The lights selected for the relevant light function are approved.
• The number of lights complies with the regulations for the vehicle’s length.
• Ensure that the mounting positions and geometric visibility are correct.
• The electrical circuit complies with the relevant requirements.
• The installation complies with the approved vehicle configuration.

You should therefore finalise the lighting configuration early in the development process, particularly where there are multiple vehicle variants.

Option 2: retrofitting to an existing O4 semi-trailer

When retrofitting additional lighting to an existing O4 vehicle, you must take national regulations into account. This is precisely where confusion often arises: national regulations for vehicles in use do not always align directly with the latest amendments to UNECE R48.

A key example is manoeuvring lights (ML). Since June 2023, UNECE R48 has also recognised this light function for trailers and semi-trailers. However, national regulations do not always specifically list manoeuvring lights as permitted lighting. As a result, retrofitting can lead to the vehicle being rejected, even if the light has the correct ML approval.

Do you need additional lighting whilst loading, unloading or carrying out other work around the vehicle? If so, separately switched work lights may be an option. Work lights are not subject to the same installation regulations as manoeuvring lights and are permitted in various countries, subject to certain conditions.

Furthermore, the lights must actually function as work lights. Simply renaming a manoeuvring light does not automatically make the installation permissible. The mounting, electrical connection and use must comply with the applicable national regulations.

Which solution is right for the application?

Does an existing heavy-duty semi-trailer have limited visibility at a loading bay? In that case, additional reverse lights with AR approval can provide a solution, provided that the mounting and wiring comply with the relevant requirements.

For loading and unloading, separately switched work lights are often the best choice. For intensive use or harsh conditions, TRALERT®’s heavy-duty work lights may be the right solution.

Who sets the regulations for vehicle lighting?

Watch the TRALERT® video on UN ECE standards and legislation for an explanation of how vehicle lighting regulations are developed and applied.

CAN-bus

Modern vehicles can monitor the operation of lighting systems electronically. Connecting additional LED lights may affect the load on an electrical circuit or the signals monitored by the vehicle. Read more about the causes and possible solutions in our article on CAN bus faults with LED lighting.

ECE R10 and electromagnetic compatibility

ECE R10 relates to the electromagnetic compatibility (EMC) of vehicles and electrical or electronic components.

These regulations are relevant to the selection and integration of LED lighting, but are separate from the specific functional approval for reversing lights and manoeuvring lights.

An ECE R10 approval therefore does not replace an AR or ML functional approval. You should also check the applicable EMC requirements for AR- and ML-approved lights.

Putting together a suitable lighting solution

Use the checklist below when selecting and integrating additional lighting.

1. Light function: reverse lights, manoeuvring light or work light.
2. Vehicle specifications: category, length, construction and intended use.
3. Product approval: the correct function code and technical documentation.
4. Mounting: position, height, visibility and protection.
5. Electrical connection: power supply, circuitry, cabling and any speed control.
6. Approval process: European type approval or national regulations for retrofitting.

You should therefore coordinate these points early on in the design process. This will help you avoid unnecessary modifications to the structure or electrical installation.

Frequently asked questions about additional lighting on O4 vehicles

How many additional reverse lights may a heavy-duty O4 semi-trailer have?

For an O4 trailer longer than 6 metres, UNECE R48 stipulates two mandatory and a maximum of two optional reverse lights. The two additional lights may be fitted at the rear or, subject to the applicable conditions, on the sides.

What is the difference between a reverse light and a manoeuvring light?

An AR-approved reverse light is intended to provide lighting whilst reversing. An ML-approved manoeuvring light illuminates the area alongside the vehicle during low-speed manoeuvres. Both functions have their own specific requirements regarding light distribution, mounting and circuitry.

How many manoeuvring lights may be fitted to an O4 trailer?

This depends on the vehicle length. Up to and including 6 metres, a maximum of two manoeuvring lights are permitted; for lengths of more than 6 metres up to and including 9 metres, a maximum of four; and for lengths of more than 9 metres, a maximum of six. These numbers apply within the relevant UNECE installation regulations.

Can a standard work light be switched on automatically when reverse gear is engaged?

You must not use a standard work light without AR approval as a reverse light. Where additional lighting is required to operate automatically when reversing, the light must be approved for that function and the installation must comply with the relevant regulations.

Are manoeuvring lights also permitted for retrofitting?

The approval of manoeuvring lights under UNECE R48 does not automatically mean that every existing O4 trailer may be retrofitted with this light function. You should therefore check the national regulations and any implications for vehicle type-approval on a case-by-case basis.

Additional lighting for heavy-duty O4 semi-trailers

TRALERT® supplies LED vehicle lighting to trailer manufacturers, bodywork companies and professional workshops. In addition to individual reversing lights and work lights, we also offer cabling, connectors and complete lighting solutions.

From product selection to integration into a vehicle, our specialists work with you to explore the technical possibilities, mounting and electrical connections.

Would you like to integrate additional lighting into a new heavy-duty semi-trailer or modify an existing O4 configuration? Please contact TRALERT® to discuss the options for your application.

View our solutions for bodybuilding

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Disclaimer:

At TRALERT®, we do our best to keep the information in this article as accurate and up-to-date as possible, including the regulations surrounding vehicle lighting. However, legislation can change regularly, and although we make every effort to implement these changes in a timely manner, it is possible that certain updates or adjustments have not yet been incorporated into this article. We therefore always advise our readers to check the current legislation with their local government or regulatory bodies, especially when it comes to exceptions or specific national regulations. TRALERT® is not liable for any damages or fines resulting from outdated or incomplete information in this article.

If in doubt, always contact the competent authority to ensure that your vehicle meets all legal requirements.