ECE R91

Standards for side marker lights on vehicles

The standard applies to side marker lights for motor vehicles and their trailers in categories M, N, O and T. This means it applies to both light and heavy vehicles, including trailers.

These side marker lights play an important role in road safety by making the sides of vehicles more visible, especially at night or in poor weather conditions. Complying with this standard helps manufacturers develop safe products that meet strict European safety requirements.

What does the regulation describe?

ECE R91 sets specific requirements for the performance of side marker lights as a product. This standard focuses on key aspects such as light intensity, colour and angle of visibility. The aim is to ensure that a side marker light performs adequately on its own to enable other road users to notice the vehicle’s position in good time.

Main requirements of ECE R91

The regulations contain guidelines for various aspects of the side marker light as a product:

• Light intensity: The lights must be clear enough to remain visible under all conditions. The standard also specifies the colour of the light(usually amber or red). And the truck procedures to be followed to ensure that the side marker lights meet the specified requirements in Candela. (For category SM1 side marker lights: minimum 4.0 cd on the reference axis).
• Visibility angle: Side marker lights must be visible from different angles so that the vehicle is clearly visible. Regardless of the position of other road users.
• Function designation: Side marker lights are classified into category SM1 or SM2. This designation on the approval mark indicates which photometric requirements the product meets.

Related topics: Read more about beams and ECE-R87 position lights.

ECE R91, ECE R148 and ECE R48: what is the difference?

ECE R91 is the older, product-specific regulation for side marker lights. For new type approvals, this light function now falls under the broader ECE R148, which combines nine previous regulations into a single type approval for light functions. Existing R91 type approvals remain valid under transitional provisions. It is also important to note that R91 and R148 regulate matters slightly differently from ECE R48: the type approval of the light itself is separate from its mounting to the vehicle.

Regulations	Role
ECE R91	Older, product-specific type approval for side marker lights
ECE R148	New, broader type approval for light signalling functions, including side marker lights
ECE R48	Vehicle installation: position, height, angle of visibility and switching

For fitting instructions – regarding where and at what height a side marker light must be fitted to the vehicle – please refer to our explanation of the difference between ECE R48 and R148.

Why is compliance with ECE R91 important?

Manufacturers must ensure that their side marker lights comply with ECE R91 to legally offer them on the European market. By following the standard, products meet legal requirements and contribute to road safety. For consumers, this means that their vehicles are equipped with lighting that meets the highest safety standards, which is especially important in poorly lit conditions.

In our article on side marker lights for trucks and semi-trailers, you can see the role ECE R91 plays in practice.

Benefits of complying with the standard

Compliance with ECE R91 regulations offers several advantages:

• Increased road safety: Standard-compliant side marker lights improve vehicle visibility, reducing the risk of accidents.
• Legal compliance: Manufacturers can offer their products on the European market without problems, which strengthens their competitiveness.
• Consumer confidence: Drivers can be confident that their side marker lights meet strict safety standards, increasing their safety on the road.

Want to find out more? Take a look at the benefits of E-mark certification and the role of the EN12352 safety standard.

Frequently asked questions about ECE R91

Why are side marker lights important for road safety?

Side marker lights make vehicles more visible from the side, especially in low visibility situations, such as during the night or in bad weather. This ensures that other road users notice the vehicle in time, reducing the risk of accidents.

Is ECE R91 still relevant?

As for existing approvals: these remain valid under transitional provisions. For new type approvals, however, R91 is no longer the applicable regulation. Side marker lights are now covered by the broader ECE R148, which has replaced R91 along with eight other older regulations.

What is the difference between ECE R91 and ECE R148?

Both regulate the type approval of the side marker light as a product. R91 is the older, specific regulation; R148 is the new, consolidated regulation that combines nine previous regulations. For new products and type approvals, R148 is the applicable framework, whilst existing R91 approvals remain valid in practice.

Does ECE R91 also specify the mounting position?

No. ECE R91 concerns the type approval of the side marker light itself, not its mounting on the vehicle. The mounting position, height and spacing of side marker lights are specified in ECE R48, a separate regulation governing the installation of vehicle lighting.

External source: For further details on ECE R91 and other lighting standards, visit the official UNECE website.