Marker lights with indicator function on O1 and O2 trailers: tips + wiring diagram

The demand for flashing side marker lights is growing in the market. It gives a modern look, but above all it provides extra safety on the road. Yet the regulations are not always clear: in some cases, blinking marker lights with indicator function are allowed, while in others they are not.

In this blog you will read:

• What the legislation is and what this means in practice
• Tips and wiring diagrams for flashing side markings
• Plug-and-play solutions for trailer manufacturers

Regulations for blinking marker lights with indicator function

European type approval (ECE R48) states that for vehicle categories O1 and O2, blinking side marker lights are not permitted upon admission. For O3 and O4 vehicles, it is mandatory in all countries that follow the ECE regulation.

In the Netherlands, different legislation applies once a trailer has been approved.

• O1 Light trailer category (≤ 750 kg): here, only direction indicators, hazard warning lights and brake lights may flash during emergency braking. The flashing of side marker lights is not permitted.
• O2 Medium-weight category trailers (> 750 kg and ≤ 3,500 kg): here the side marker lights may flash in synchronisation with the direction indicators.

• O3 Heavy trailer category (> 3,500 kg and ≤ 10,000 kg):
  Since 1 January 2025, newly registered O3 trailers must have mandatory side marker lights that flash synchronously with the direction indicators.
• O4 Category of very heavy trailers (> 10,000 kg):
  The new obligation also applies here: from 1 January 2025, all newly registered O4 trailers must be equipped with flashing side marker lights (or a separate side direction indicator). Existing vehicles do not have to be retrofitted.

Supporting sources: RDW, RAI Association Bodybuilding

Why sequential side lighting is becoming increasingly popular

We are experiencing increasing demand for flashing side marker lights. This gives a professional look and feel in the field and significantly increases road safety. The vehicle is more visible to other road users. This greatly reduces the risk of accidents involving vulnerable road users, such as cyclists and pedestrians. In the context of safe working, the article reverse work lights on trailers may also be of interest to you, in which we also explain, among other things, how to connect them.

Since 1 January 2025, flashing side lighting is mandatory for newly registered O3 and O4 trailers. More on this in the article on trailer lighting rules.

Connecting marker lights with indicator function

There are two common ways of flashing the side marking.

Option 1: Via an extension cable + control unit

This wiring diagram shows an example of how the side markings can be connected using a control unit. We see a 7-PIN connector with 1.5 extension cable + 3-pole Superseal input + 2-pole SuperSeal output. This taps the indicator and position light signal without risk of interference.

* Wiring diagram for blinking marker lights with indicator function

Option 2: directly via multifunctional rear lights

Do you want to connect marker lights with indicator functions in a simple and clear way? Then using a multifunctional rear light with multiple SuperSeal connections is a smart and efficient solution. These rear lights allow you to connect multiple functions via one central unit. Think of:

• Flashing side lighting
• Side marker lighting
• Licence plate light
• Third brake lamp
• Reversing worklight

This solution not only makes the installation clear, but also saves you valuable time on the production floor. No separate branching or additional cabling is required. You work directly from the rear light, completely plug & play.

For example via the VC 2000 or VC 6000 series, with built-in control unit and multiple SuperSeal connections. Ideal for OEM and trailer manufacturers looking for speed and simplicity.

* Wiring diagram to connect marker lights with indicator function to a multifunctional rear light. The VC 2000 series is shown on the left and the VC 6000 series on the right.

Plug & play solutions with complete wiring harnesses

TRALERT® is all about smart simplicity, which is why we offer complete lighting solutions. These plug-&-play solutions allow you to save time and costs when installing lighting. This means minimal installation time and less susceptibility to error. Whether you work with a standard wiring harness or a customised solution for your vehicles, installation is always quick and straightforward.

Fully canbus compatible

The marker lights with indicator function should work seamlessly with the other lighting. To ensure that the side lighting is both continuous and synchronous with the direction indicator without interference. This is also known as canbus / interference-free lighting.

Made-to-measure for trailer manufacturers

Are you a trailer builder looking for a suitable lighting solution?
Ask for a non-binding consultation with one of our product specialists.

• Technical support and schemes
• Mounting and demonstration videos
• Engineering support for customisation

Regulations for blinking marker lights with indicator function

Marker lights with indicator function are no longer just an attractive addition - they are the new standard. Since 2024, it is mandatory for all new O3 and O4 trailers within the EU to use side lighting that flashes synchronously with the direction indicators. But even on smaller trailers (where it is not mandatory), this dynamic side lighting offers direct added value. It increases visibility, improves safety and gives the trailer a modern, professional look.

More on this in our complete overview of trailer lighting regulations.

Frequently asked questions

What are marker lights with indicator function?

Marker lights with indicator function are side lights that flash synchronously with the trailer's direction indicator. They increase visibility and safety.

Are marker lights with indicator function mandatory for all trailers?

No, only for new vehicles in the O3 and O4 categories within the EU.

How do I connect marker lights with indicator function to 12V or 24V?

This can be done via a Canbus control box or via the rear light with SuperSeal connector. View our schemes or request support if you are a wagon builder.

Is a Canbus control box always necessary?

In modern vehicles, a Canbus control box prevents error messages and ensures correct signal processing. Definitely recommended.

Do flashing side lights comply with ECE R48?

Yes, our systems comply with the placement requirements and specifications of ECE R48 regulation for side markings on 12V trailers.