Mandatory towing lights: Everything you need to know

On the road, visibility is non-negotiable. Especially when you're towing a trailer. Because it doesn’t matter if you’re transporting a motorcycle, a work cart, or a full caravan — if you don’t have the right lights, you’re exposing yourself to serious danger. Not just because of a fine, but because you're putting your safety and that of others at risk.

Why are trailer lights mandatory?

On the road, other drivers don’t guess. They need to see in order to react. Trailer lights are not there for decoration: they’re your only way to communicate with the vehicles behind you when you brake, turn, or simply drive at night.

This is not just about good practice — it’s about legality. If the lights don’t work, or if they’re missing altogether, you’re guaranteed to get fined. And your vehicle could be immediately immobilized during an inspection. Is it worth the risk?

What lights must a trailer have?

Here’s where things get more technical. Although regulations may vary slightly depending on the country, in Spain and much of Europe, the requirements are clear.

• Rear lights: at least two, with three basic functions — position light, brake light, and turn signal. It’s the ABC of trailer lighting.
• License plate light: without it, your plate becomes invisible at night. And that’s illegal.
• Reflectors: they don’t emit light but reflect that of others. Mandatory. Always. And they must be red if placed at the rear.
• Rear fog light: required for trailers with a maximum authorized mass (MAM) over 750 kg. Because when the fog rolls in, only the light remains.
• Reverse light: also required from 750 kg upward. It warns others that the trailer is moving backward.
• Side marker lights: mandatory on trailers wider than 1.60 m. They help others perceive the trailer’s true dimensions.

And what about the front? In some cases, yes. If the trailer protrudes or is particularly wide, it will need white front position lights. Although it's not very common, better to know than to ignore it.

The connection: plugs and compatibility

What’s the point of having lights if you don’t connect them properly? A trailer’s lighting system depends on the towing vehicle. Both must be synchronized.

This is where connectors come into play. The most common are:

• 7-pin: the standard for light trailers. Covers the basics.
• 13-pin: more complete. If your trailer has reverse light, fog light, or auxiliary power, you’ll need this one.

Not compatible? No problem. There are adapters. But never improvise. The electrical installation of a trailer is just as serious as that of a car.

Do the lights need to be approved?

Yes, and just turning on isn’t enough. They must be approved according to European regulations (ECE Regulation R48) and properly installed.

Also, any modification must be reported. If you install new lights, change the electrical system, or add elements that affect the trailer’s visibility, you’ll need to pass a vehicle inspection (ITV).

And beware of cheap LED kits from the internet. Many don’t meet the legal requirements. If they don’t have CE marking and regulatory reference, they’re not valid.

Maintenance

Few things fail as often — and are checked as little — as trailer lights. They’re exposed to moisture, dust, impacts, connector corrosion, and electrical faults. It’s a vulnerable system. That’s why every time you use your trailer, do a quick visual check. It only takes a couple of minutes, but it could save you a major headache.

Do all the lights turn on? Are the indicators blinking correctly? Are the connections tight? Is there water inside the housings? It may sound like a lot, but it’s just routine. And with routine, problems are prevented.