LED Side Marker Lights for Trailers

UK Legal Requirements, Benefits and Best Practice


Lucidity ultra-slim LED side marker light fitted to a trailer

LED side marker lights play a crucial role in trailer safety, compliance and visibility — yet they’re often overlooked until something goes wrong at a roadside check.

Whether you’re running a commercial trailer fleet, manufacturing trailers, or maintaining equipment in a workshop, understanding when side marker lights are required, what makes them legal, and why LED technology is now the industry standard is essential.

This guide explains everything you need to know about LED side marker lights for trailers in the UK, including legal requirements, fitting guidance, and why ultra-slim LED designs are increasingly popular.

What Are Side Marker Lights on a Trailer?

Side marker lights (also known as marker lamps) are amber or white lights fitted along the side of a trailer to improve visibility, particularly in:

  • Low light conditions
  • Poor weather
  • Urban environments
  • When turning or changing lanes

Their primary function is to clearly show the length and presence of the trailer to other road users.

Are Side Marker Lights a Legal Requirement in the UK?

Yes — side marker lights are a legal requirement on many trailers in the UK.

Under the Road Vehicles Lighting Regulations 1989, trailers must be fitted with side marker lights when they exceed certain dimensions.

This legislation is enforced by:

  • DVSA (Driver and Vehicle Standards Agency)
  • GOV.UK

When Are Side Marker Lights Required?

Side marker lights are mandatory on trailers that are:

  • Over 6 metres in length (excluding the drawbar)
  • First used on or after 1 April 1991

They must:

  • Be amber in colour (or white at the front)
  • Be evenly spaced along the trailer
  • Clearly indicate the trailer’s length and outline

Shorter trailers may not legally require side markers, but fitting them is still considered best practice for safety and visibility.

Why LED Side Marker Lights Are Now the Industry Standard

Traditional filament marker lamps are rapidly being phased out in favour of LED side marker lights — and for good reason.

Key Advantages of LED Marker Lights

  • Improved visibility – brighter, cleaner light output
  • Low power consumption – ideal for modern vehicles
  • Long service life – often tens of thousands of hours
  • Vibration resistant – perfect for plant and commercial trailers
  • Fully sealed units – resistant to water, dirt and road salt
  • Slimline designs – easier installation on modern trailer bodies

For fleet operators, LEDs also mean less downtime, fewer failures and reduced maintenance costs.

E-Marking and Legal Compliance

What Is E-Marking?

All LED side marker lights used on UK roads must be E-marked.

E-marking confirms the light:

  • Meets ECE Regulations
  • Is approved for road use
  • Emits the correct colour and intensity
  • Is suitable for its intended function

Using non-approved marker lights can result in:

  • DVSA prohibitions
  • Failed inspections
  • Insurance issues
  • Trailer downtime

Clear vs Amber Side Marker Lights

A common question is whether clear lens side marker lights are legal.

The answer is yes, provided:

  • The emitted light is amber
  • The unit is E-marked
  • It meets intensity and visibility requirements

Clear lens LED side markers are popular because they:

  • Look cleaner on modern trailers
  • Match aluminium, galvanised and painted bodies
  • Reduce visual clutter
  • Remain fully compliant

Recommended LED Side Marker Lights from Trailer Solutions

At Trailer Solutions, we stock professional-grade Lucidity LED side marker lights designed specifically for UK road use.

Lucidity 26285 Ultra-Slim LED Side Marker Light

The Lucidity 26285 is ideal for modern trailers where space is limited.


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  • Ultra-slim profile
  • Clear lens with amber output
  • Fully E-marked
  • Sealed LED unit
  • Ideal for plant, flatbed and commercial trailers

This light is popular with manufacturers and refurbishers looking for a clean, discreet finish without compromising compliance.

Lucidity 26287 LED Marker Lamp – Clear Side Trailer Light

The Lucidity 26287 offers a slightly more traditional footprint while retaining all the benefits of LED technology.


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  • Clear lens with amber emission
  • Robust housing
  • E-marked for UK road use
  • Excellent visibility
  • Suitable for a wide range of trailer types

A great choice for fleet replacements, servicing and retrofits.

Correct Positioning of Side Marker Lights

To remain compliant, side marker lights must be:

  • Mounted symmetrically
  • Clearly visible from the side
  • Not obscured by bodywork, equipment or loads
  • Securely fixed

On longer trailers, multiple marker lights must be evenly spaced to clearly show the trailer’s length.

Common Side Marker Light Faults Found at Roadside Checks

  • Non-functioning marker lights
  • Incorrect colour output
  • Poor wiring or earth faults
  • Damaged lenses
  • Non-approved light units

Upgrading to sealed LED units dramatically reduces these failures.

Why Buy LED Marker Lights from Trailer Solutions?

All LED side marker lights supplied by Trailer Solutions are:

  • Fully E-marked
  • Suitable for UK road use
  • Tested for durability
  • Ideal for trade, fleet and professional applications

We specialise in quality, compliant lighting — not cheap imports that risk downtime or enforcement action.

Final Thoughts

LED side marker lights are not just a styling upgrade — they are a key safety and legal requirement for many trailers operating on UK roads.

Choosing high-quality, E-marked LED marker lights:

  • Improves safety
  • Reduces maintenance
  • Ensures compliance
  • Protects your business and drivers

If you’re upgrading, repairing or building trailers, investing in the right LED side marker lights is a simple but vital step.