End Outline Marker Lamps: What They Are and When You Need Them

What an End Outline Marker Lamp Is

An end outline marker lamp is a small fixed lamp fitted near the outer edge of a wide vehicle to mark its extreme width to other road users. The lamp shows white to the front and red to the rear. Many corner lamps also include an amber side element, which is a separate side marker function. End outline marker lamps appear on wide agricultural trailers, lorries, slurry tankers, bale carriers, and self-propelled sprayers.

The Road Vehicles Lighting Regulations 1989 define the end outline marker lamp as a lamp fitted near the outer edge of a vehicle to indicate its overall width, with its own fitting rules in Schedule 13. The lamp is small, low-powered, and lit whenever the vehicle’s position lamps (sidelights) are on. It is not a hazard warning light. It does not flash and it does not signal direction.

An end outline marker lamp differs from a side marker light in two ways. A side marker light sits along the middle of the vehicle and marks its length. An end outline marker sits at the extreme corner and marks its width. The two types work together on long, wide vehicles to give a complete outline at night. The side marker lights article covers the side marker function in full.

When UK Law Requires End Outline Markers

UK law requires end outline marker lamps on motor vehicles wider than 2.1 metres first used on or after 1 April 1991, unless the vehicle has a maximum speed of 25 mph or less, and on trailers wider than 2.1 metres made on or after 1 October 1990. The requirement is in Schedule 1 of the Road Vehicles Lighting Regulations 1989, with the fitting rules in Schedule 13. Older vehicles can fit end outline markers as an optional safety feature but do not have to.

Agricultural vehicles are treated differently. Agricultural trailers and trailed appliances are exempt from the end outline marker requirement, and so is any tractor with a maximum speed of 25 mph or less, which covers most 40 km/h tractors. A faster tractor (50 km/h or more) over 2.1 metres wide and first used from 1 April 1991 does need them. Fitting them to a wide grain trailer is still good practice, and any that are fitted must work.

The lamp is required at four positions on every qualifying vehicle. Two lamps at the front (one near each outer edge) and two lamps at the rear (one near each outer edge). Vehicles over 6 metres long also need side marker lamps along the body in addition to the end outline markers at the corners.

Using a vehicle on a road without its obligatory lamps working is an offence, which can lead to a fixed penalty or prosecution. Lorries and heavy trailers that take an annual test will fail it with a missing or non-working obligatory end outline marker. Farm tractors in the agricultural tax class and agricultural trailers do not take an MOT, but any marker lamp that is fitted must still work.

Colour and Position Rules

End outline markers must show white to the front and red to the rear. The colour rule comes from the Road Vehicles Lighting Regulations 1989 and matches the colour logic used on other position lamps: white forward and red rearward. Amber to the side belongs to side marker lamps, a separate function that is often built into the same corner lamp.

A typical wide trailer carries four end outline marker lamps in pairs. The front pair shines white through a clear or white lens. The rear pair shines red through a red lens. Many marker lamps combine two colours in a single body using a divider inside the lens, so one lamp on the front corner shows white forwards and amber sideways simultaneously.

The amber side element on a combined corner lamp can act as one of the vehicle’s side marker lamps where it is approved for that function. Vehicles that need side markers (generally those over 6 metres long) must have them spaced along the body, not just at the corners. The position lamps article explains the sidelight logic that the marker rule builds on.

Mounting Height and Distance from the Vehicle Edge

Mount end outline markers no more than 400mm in from the side of the vehicle. At the front of a motor vehicle, the top of the lit area must be no lower than the top of the windscreen. At the front of a trailer and at the rear of any vehicle, the lamps go as high as the width rule and the vehicle’s use allow. Both rules come from Schedule 13 of the 1989 Regulations.

The 400mm lateral rule means the marker lamp must sit on or near the corner of the vehicle. A grain trailer 2.5 metres wide measured outer edge to outer edge needs its front marker lamps positioned no further than 400mm inward from each outer edge. On a typical trailer this places the lamps directly on the corner uprights.

The point of the height rule is to mark the top corners of the vehicle as well as its width, so other drivers can judge its size. On a tall trailer the rear pair sits near the top of the structure, not down at bumper height.

LED vs Filament End Outline Marker Lamps

LED end outline markers draw 0.1A and last 30,000 hours, while filament markers draw 0.4A and last 1,000 hours. The power and lifespan difference is the main reason farms upgrade their trailer marker fleet from filament to LED.

A typical wide agricultural trailer fitted with eight filament markers (four end outline, four side) draws 3.2A at 12V from the trailer plug. The same trailer fitted with LED markers draws 0.8A. The difference matters when the tractor plug is also feeding flasher lamps, brake lights, and a sidelight circuit on a long umbilical cable.

LED markers also survive vibration better than filament markers. The LED has no fragile tungsten filament to fracture under the constant shake of a loaded trailer on a rough field track. Most LED markers carry an IP67 or IP69K rating, sealing the LED, the resistor, and the connector against silage juice, slurry splash, and pressure-washer cleaning.

Filament markers still have one advantage: they are cheaper to buy. A C5W filament marker costs £3 to £5. An LED equivalent costs £8 to £15. The total cost over a trailer’s working life favours LED because the LED outlasts 15 to 30 filament replacements.

Common Fitment Scenarios on Farm Vehicles

Common fitments include wide agricultural trailers, bale carriers, silage trailers, self-propelled sprayers, slurry tankers, and beet harvesters. Each application uses end outline markers in slightly different positions because the vehicle shape differs.

A flatbed grain trailer carries four corner markers (two front, two rear) and side markers along the sides if the length exceeds 6 metres. A bale carrier with a flared chassis fits the markers on the outer leg tubes at the front and rear corners. A silage trailer with high sides fits the front markers on the upper headboard so they sit above the cab when the trailer is hitched.

A self-propelled sprayer wider than 2.1 metres fits front end outline markers on the cab roof corners and rear markers on the boom hinge brackets. A slurry tanker fits markers on the front A-frame and the rear platform rail. A beet harvester fits markers on the lifter frame and the cleaner-loader bed.

A tractor with a maximum speed of 25 mph or less does not need end outline markers, whatever its width. A faster tractor (50 km/h or more) over 2.1 metres wide, first used from 1 April 1991, does. Adding dual wheels can take a tractor past 2.55 metres, where the special-type rules on speed and width apply, so some farms fit removable marker lamps on the dual wheel arms for road movement.

Installing and Wiring End Outline Markers

Wire end outline markers to the vehicle’s sidelight circuit using 1mm cable and weatherproof connectors. The markers must come on whenever the sidelights come on and stay on through dipped beam and main beam operation. They do not switch with the ignition alone, and they do not flash with the indicators.

The trailer plug carries the sidelight feeds on dedicated pins. On a 7-pin 12N (ISO 1724) plug, pin 5 (brown wire) feeds the right-hand (offside) tail lamps and pin 7 (black wire) feeds the left-hand (nearside) tail lamps. Marker lamps wire into these two feeds depending on which side of the trailer they sit. On a 13-pin (ISO 11446) plug the same pins are used: pin 5 right-hand and pin 7 left-hand.

Cable runs along the trailer chassis inside a corrugated conduit or a stainless steel braid. Each marker connects to the main run using a Scotchlok or a sealed butt-splice connector. Avoid open spade terminals because moisture seeps in and corrodes the contact within one or two seasons.

The earth return runs back through the trailer chassis or through a dedicated earth wire to the tractor plug. Modern LED markers prefer a dedicated earth wire because chassis earths develop high resistance over time as paint and rust build up between the lamp body and the chassis steel. The agricultural trailer lighting requirements article covers the full trailer wiring layout.

Choosing and Buying End Outline Markers

Choose end outline markers by matching the vehicle width, the mounting position, and the trailer voltage. Most UK agricultural trailers run on 12V from the tractor plug. A handful of larger continental trailers run on 24V from heavy-duty plant tractors. Many LED markers are rated for both 12V and 24V on the same body; check the marking before fitting.

Lens shape matters. A flat-lens marker sits flush against the chassis or upright. A bullseye lens projects outward and gives wider side visibility but catches branches and gateposts. A combined twin-lens marker shows two colours from a single body and saves wiring on corner positions.

Look for the E-mark on the lamp body. The E-mark shows the lamp is approved to ECE Regulation 7, which covers position lamps, stop lamps and end outline marker lamps. The regulations require an approval mark on obligatory end outline marker lamps, so buy E-marked lamps for road use. The full Agri Lighting universal marker lamps range lists every approved lamp by voltage, colour, and mounting type.

End outline marker lamps are small, cheap, and easy to overlook. Fitted correctly, they keep a wide trailer visible at the boundary of its footprint. Missed or broken, they expose the operator to enforcement action, annual test failures on lorries and heavy trailers, and the genuine risk of a collision where an oncoming driver misjudges the trailer’s width in the dark.