Position Lamps: Front and Rear Sidelights Explained

A position lamp is the sidelight on a car: a low-power lamp that shows white at the front and red at the rear to mark where the vehicle is and how wide it is. A car has 2 front position lamps and 2 rear position lamps. They come on at the first click of the light switch and stay on with dipped and main beam.

What Is a Position Lamp on a Car

A position lamp is a low-intensity light that marks the presence and width of a vehicle to other road users. The Road Vehicles Lighting Regulations 1989 (RVLR) define a front position lamp as a lamp used to indicate the presence and width of a vehicle when viewed from the front, and a rear position lamp as the same when viewed from the rear. They are the dimmest exterior lamps on a vehicle, because their job is to be seen, not to light the road.

“Position lamp” is the official name used in UK regulations and on MOT test results. The same lamp goes by several other common names:

• Sidelight: the everyday UK term. “Put your sidelights on” means switch on the position lamps.
• Parking light: used more in American English, and in the Highway Code rules on parking at night.
• Position light: used in some vehicle handbooks and European documents.
• Tail light: the usual name for the rear position lamps specifically.

Position lamps are separate from headlights (which light the road ahead), brake lights (which signal braking) and indicators (which signal turning). Once the lights are switched on, the position lamps stay on from the sidelight stage right through dipped beam and main beam.

Front vs Rear Position Lamps

Feature	Front position lamp	Rear position lamp
Colour	White (or yellow if built into a yellow headlamp)	Red
Number required	2	2
Usual location	Inside the headlamp unit	Inside the rear lamp cluster
Common bulb	W5W (501)	P21/5W (380) or R5W (207)
Typical wattage	5W	5W
Other names	Sidelight, front parking light	Tail light, rear sidelight

Front Position Lamps

A front position lamp is a white light fitted to each side of the front of a vehicle. Its job is to show oncoming traffic and pedestrians where the edges of the vehicle are.

On most modern cars, vans and tractors, the front position lamp sits inside the headlamp unit, using its own small bulb or LED element. On older vehicles, particularly classic tractors, the front position lamp is often a separate lamp mounted on the front mudguard or wing.

A typical front position lamp uses a 5W bulb. That is deliberately low. On many modern cars the front position lamp is combined with the daytime running light, which runs at full brightness in daylight and dims to position lamp level when the headlights come on. Our guide to daytime running lights explains how that switching works.

Rear Position Lamps

A rear position lamp is a red light fitted to each side of the rear of a vehicle. It shows following drivers the width of the vehicle in front.

Rear position lamps almost always sit in the rear lamp cluster with the brake lights, indicators, reverse light and (where fitted) rear fog lamp. The rear position lamp is the dim, constant red glow when the lights are on. The brake light is the brighter red that appears when the brake pedal is pressed. The rear position lamp runs at about 5W; a brake light filament is 21W.

On many vehicles, the rear position lamp and brake light share 1 twin-filament bulb, the P21/5W (trade code 380). The thin 5W filament powers the position lamp and the thicker 21W filament powers the brake light. That is why a fault with one of these bulbs can affect both functions.

Nearside and Offside Position Lamps

MOT results and garage paperwork describe lamps by side:

• Nearside: the left side of the vehicle, the passenger side in a UK right-hand-drive car, nearest the kerb.
• Offside: the right side of the vehicle, the driver side in a UK car, nearest the centre of the road.

Left and right are always as if you are sitting in the driver’s seat facing forward, and the terms do not change for a left-hand-drive import: nearside is still the left. So:

MOT wording	Which lamp
Nearside front position lamp	Front left sidelight (passenger side)
Offside front position lamp	Front right sidelight (driver side)
Nearside rear position lamp	Rear left tail light
Offside rear position lamp	Rear right tail light

The terms come from horse-drawn days: the nearside was the side nearest the kerb. If your MOT says one of these lamps is not working, our guide to a position lamp not working walks through the fix and the retest.

Position Lamps vs Daytime Running Lights vs Dipped Beam

Position lamps are often confused with the other front lamps that come on with the engine or the light switch. The difference is what each lamp is for.

Lamp	Purpose	When it is on	Lights the rear lamps?
Front position lamp (sidelight)	Shows the vehicle’s position and width	When the light switch is on (sidelight, dipped or main beam)	Yes, rear position lamps come on with it
Daytime running light	Makes a moving vehicle easier to see in daylight	Automatically with the engine, off or dimmed when headlamps are on	Not necessarily; on many cars the tail lights stay off
Dipped beam headlamp	Lights the road ahead without dazzling	At night and in seriously reduced visibility	Yes

The practical point: a car running only on DRLs at dusk may have no tail lights lit at all. Switch to dipped beam (which brings on the position lamps front and rear) as soon as the light starts to fade.

UK Legal Requirements for Position Lamps

RVLR requires front and rear position lamps on almost every motor vehicle and trailer. The main exceptions are that a solo motorcycle with a headlamp does not need a front position lamp, and trailers no wider than 1,600 mm (and some older, short trailers and boat trailers) do not need front position lamps. Rear position lamps have no exceptions for motor vehicles or trailers.

Minimum Requirements

• 2 front position lamps (white), 1 on each side of the front
• 2 rear position lamps (red), 1 on each side of the rear

Under the European installation rules (ECE Regulation 48), position lamps on a car are mounted between 350 mm and 1,500 mm above the ground and no more than 400 mm in from the outer edge of the vehicle, so that together they mark its width.

When Position Lamps Must Be Used

• Between sunset and sunrise: Highway Code rule 113 says you MUST ensure all sidelights and rear number plate lights are lit.
• At night on lit roads: you must use headlights at night except on a road with lit street lighting, so sidelights alone are permitted on a lit road, usually a 30 mph road (20 mph in Wales). Most drivers use dipped headlights anyway, and rule 115 says to use dipped headlights (or dim-dip) at night in built-up areas.
• Parked at night: rule 249 says all vehicles MUST show parking lights when parked on a road or lay-by with a speed limit over 30 mph. Under rule 250, cars and goods vehicles up to 2,500 kg laden weight may park without lights on a road of 30 mph or less if they are at least 10 metres from a junction, close to the kerb and facing the direction of traffic, or in a recognised parking place or lay-by. Trailers and vehicles with projecting loads must not be left on a road at night without lights.

Penalties

Using a vehicle at night without working position lamps is an offence and can lead to a fixed penalty or a defect notice. A tractor or trailer with no rear lights on an unlit lane at night is one of the most dangerous things on a rural road.

Position Lamps and the MOT

The MOT checks every mandatory position lamp for operation, colour, condition, security and switching. A position lamp that does not work is a major defect, which is an MOT fail, not an advisory.

Defect (MOT section 4.2)	Category
Lamp missing or inoperative	Major (fail)
LED lamp with more than half its light sources out	Major (fail)
LED lamp with up to half its light sources out	Minor
Defective lens	Major (fail)
Rear position lamps can be switched off with headlamps on	Major (fail)
Colour, position or intensity not as required	Minor
Red light showing to the front, or white light to the rear	Major (fail)
Lamp not secure / likely to fall off	Minor / Major

The MOT accepts a front position lamp that is white, predominantly white with a blue tinge, or yellow when built into a yellow headlamp. A strongly coloured “ice blue” LED sidelight is a different matter and can be recorded as a colour defect. Rear position lamps must give a steady red light.

Position Lamp Bulb Types

The most common position lamp bulb in UK cars is the W5W, a 5W capless wedge bulb also sold as 501. Most front sidelights use it, and many rear clusters and number plate lamps do too.

Bulb	Trade code	Base	Wattage	Typical use
W5W	501	W2.1×9.5d capless wedge (often called T10)	5W	Front sidelights on most cars and vans; some rear position lamps
R5W	207	BA15s bayonet	5W	Older front sidelights, separate rear position lamps, trailer and tractor lamps
H6W	434	BAX9s offset-pin bayonet	6W	Front sidelights on some European cars
P21/5W	380	BAY15d bayonet (offset pins)	5W position / 21W brake	Combined rear position and brake lamps
LED	None	Built into the lamp, or an LED replacement bulb	Under 1W to a few watts	Many cars from the 2010s, LED trailer and tractor lamps

The W5W pushes straight into its holder. The R5W pushes in and twists to lock, like a small version of a brake light bulb. The P21/5W has offset pins so it only fits one way round, which keeps the 5W filament on the position lamp circuit and the 21W filament on the brake circuit. See our guides to W5W 501 bulbs and R5W 207 bulbs for the details of each, and find replacements in our standard miniature bulbs range.

LED Sidelight Bulbs

LED W5W and R5W bulbs are widely sold. They last longer and resist vibration, but most are not type approved for use in a lamp designed for a filament bulb, and on cars with bulb monitoring they can trigger a “bulb failure” warning unless they are CANbus compatible. If you fit one, choose a plain white bulb (not blue) and check it lights evenly through the lens. The more robust answer on trailers and tractors is a complete, E-marked LED position lamp.

Position Lamp Faults

A position lamp that stops working is almost always 1 of 4 things:

• Blown bulb: by far the most common. One lamp out, the others fine.
• Corroded holder: the lamp flickers, works when tapped, or the new bulb still does not light. Clean the contacts and protect them with a little dielectric grease.
• Blown fuse: on many cars, all the sidelights on one side (or all of them) go out together. Replace with the same rating; if it blows again, look for a short.
• Wiring or earth fault: more common on tractors and trailers, where vibration, chafing and rodents damage looms. A lamp that cuts out over bumps is usually a wiring fault.

If the MOT has flagged a lamp, the not-working guide linked above covers each fix step by step.

Position Lamps on Tractors and Trailers

Tractors and agricultural trailers need front and rear position lamps for road use at night, just like cars. A tractor without working position lamps is not road legal after dark.

Tractors

Modern tractors build the front position lamps into the headlamp or bonnet lamps and the rear position lamps into the rear lamp clusters on the mudguards. Older tractors often have separate sidelights on the front wings, which are exposed to hedges, loaders and implements and are often knocked off. Replacement universal sidelights are a simple bolt-on job.

Trailers

Every trailer must have 2 red rear position lamps, and trailers wider than 1,600 mm also need 2 white front position lamps. On both the 7-pin 12N socket and the 13-pin socket, the rear position lamps are fed through pin 5 (right-hand side) and pin 7 (left-hand side). Trailer lamps take a beating from spray, mud and pressure washing, so LED lamps are a worthwhile upgrade. Browse our position lamps for universal front and rear units.

Practical Tips

Position lamps on farm vehicles fail more often than on cars because of vibration, moisture and less frequent checks. Walk round before any road journey in the dark, and keep a spare W5W and P21/5W in the cab.

Frequently asked questions

What is a position lamp on a car?

It is the sidelight: a low-power white lamp at the front and red lamp at the rear that marks the vehicle’s position and width. A car has 2 at the front and 2 at the rear.

What is a front position lamp?

A front position lamp is the front sidelight, usually inside the headlamp unit, showing white. Most use a W5W (501) bulb.

What is a rear position lamp?

A rear position lamp is the tail light, the dim red light at the back that is on whenever your lights are on. It often shares a P21/5W (380) twin-filament bulb with the brake light.

Is a position lamp not working an MOT fail?

Yes. A missing or inoperative mandatory position lamp is a major defect, so the vehicle fails until it is repaired.

Which side is the nearside position lamp?

Nearside is the left side of the vehicle (the passenger side on a UK car). Offside is the right side, the driver side.