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, red to the rear, and amber to the side, giving an approaching driver, an overtaking driver, and a following driver three different signals of where the vehicle ends. 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 category of position lamp used specifically to indicate the maximum width of a vehicle. The lamp is small, low-powered, and always on whenever the vehicle’s 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 every vehicle wider than 2.1 metres registered after 1 October 1990. The Road Vehicles Lighting Regulations 1989 Schedule 6 sets the 2.1 metre threshold and the post-1990 registration cut-off. Vehicles registered before this date can fit end outline markers as an optional safety feature but do not have to.
Agricultural vehicles fall under the same width threshold but with one exception. Tractors and agricultural trailers used only on private farmland do not require any road lighting. The moment the same tractor or trailer enters a public road, the lighting rules apply. A 2.5 metre wide grain trailer needs end outline marker lamps the second it leaves the field gate.
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.
Fines for missing or non-working end outline markers fall under the same category as a missing sidelight: a fixed penalty notice of £100 and three penalty points if the vehicle is on a public road in darkness. The MOT tester also fails any vehicle with a non-working or cracked end outline marker lamp.
Colour and Position Rules
End outline markers must show white to the front, red to the rear, and amber to the side. The colour rule comes directly from the Road Vehicles Lighting Regulations 1989 and matches the colour logic used across every other position lamp on a UK vehicle: white forward, red rearward, amber sideward.
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 end outline marker lamp counts as the vehicle’s side marker for the first 6 metres of length. Vehicles longer than 6 metres need separate amber side markers fitted at intervals along the body. The position lamps article explains the white-red-amber sidelight logic that the marker rule builds on.
Mounting Height and Distance from the Vehicle Edge
Mount end outline markers within 400mm of the vehicle’s widest point and between 350mm and 2.1 metres above the road. The 400mm rule sets the lateral position. The 350mm to 2.1m rule sets the vertical position. Both come from Schedule 6 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 350mm minimum height keeps the lamp clear of road spray, low boundaries, and accidental contact with kerbs or bollards. The 2.1 metre maximum height keeps the lamp within the driver’s eye line for following vehicles. Trailers taller than 4 metres can optionally fit a second pair of end outline markers at the top of the structure, but the lower pair below 2.1 metres remains mandatory.
Mounting the lamp on the rear of a wide trailer needs the same 400mm lateral rule but the height rule loosens. Rear end outline markers can sit anywhere between 350mm and 4 metres above the road provided one pair sits below 2.1 metres.
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 headboard and tailgate 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 wide tractor without a trailer also needs end outline markers if the tractor itself exceeds 2.1 metres in width. Most standard-track tractors sit just under 2.1 metres without dual wheels. Adding dual wheels for cultivation widens the tractor to 2.6 metres or more, which triggers the marker rule. 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 feed on a dedicated pin. On a 7-pin 12N plug, pin 5 (white wire) feeds the offside rear sidelight and pin 7 (black wire) feeds the nearside rear sidelight. Marker lamps wire into these two feeds depending on which side of the trailer they sit. On a 13-pin Euro plug, pin 1 feeds the left sidelights and pin 2 feeds the right.
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. LED markers carry both voltage ratings on the same body, switching automatically between 12V and 24V input.
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 proves the lamp meets the ECE Regulation 7 standard for position lamps. Lamps without an E-mark cannot be used legally on a UK road. 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 farm to fines, MOT failures, and the genuine risk of a collision where an oncoming driver misjudges the trailer’s width in the dark.
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