Agricultural Trailer Lighting Requirements in Ireland: Lamps and Markers

Agricultural trailer lighting requirements in Ireland come from the Road Traffic (Lighting of Vehicles) Regulations 1963, as amended by S.I. No. 249 of 2014, which came into force on 1 January 2016. An agricultural trailer drawn by a tractor must have side lamps, rear lamps, stop lamps, direction indicators and number plate lighting. A side marker lamp is needed when the tractor and trailer combination is over 10 m long, and trailers over 3,500 kg design gross vehicle weight need reflective markings.

That is a bigger list than many farmers expect, and stop lamps and indicators are not optional on an Irish farm trailer. This guide covers each lamp and marking in turn, with colours and practical mounting advice, then lighting boards for towed equipment, the 7-pin and 13-pin plug, wide and long trailers, and what gets checked at the roadside.

Which rules apply to agricultural trailers

The principal rules are the Road Traffic (Lighting of Vehicles) Regulations 1963 (S.I. No. 189 of 1963), amended many times since. The main agricultural reform is the Road Traffic (Lighting of Vehicles) (Amendment) Regulations 2014 (S.I. No. 249 of 2014), part of the package the RSA calls the “Revised Standards for Agricultural Vehicles”. It brought in the trailer lamp list, side marker lamps over 10 m, reflective markings and lighting boards, all from 1 January 2016.

The same 2016 package also introduced braking standards, plating and speed discs for agricultural trailers. Trailers first registered on or after 1 January 2016 must carry a national authorisation plate and a speed disc showing their design speed in km/h at the rear. Widths and weights are set out in the RSA’s agricultural vehicles weights and dimensions leaflet. For the tractor side of the rules, see tractor lighting law, and the RSA’s own summary is on its lighting and visibility laws for agricultural vehicles page.

Agricultural trailer lights: the lamp-by-lamp table

The table below shows what an agricultural trailer drawn by a tractor needs on an Irish public road. The positions column gives good practice; where the Irish rules set a figure, it is stated.

Lamp or reflector	Required on an agricultural trailer?	Colour	Number	Position and notes
Rear lamps (tail lights)	Yes	Red	2	One at each rear corner, as close to the outer edge as the body allows
Stop lamps	Yes	Red	Usually 2	Worked by the tractor’s service brake; normally combined with the tail lamp
Direction indicators	Yes	Amber	1 rear on each side	Flash in time with the tractor’s indicators and with the hazard switch
Side lamps (front position lamps)	Yes	White	2	Front corners, facing forward, near the outer edge
Number plate lighting	Yes	White	As needed	Must light the rear plate; wired with the tail lamps
Side marker lamp	Yes if the combination is over 10 m	Amber	At least 1	RSA guidance describes a marker lamp on the right-hand side; UN/ECE-compliant on trailers made from 1 January 2016
Rear reflective markings	Yes if over 3,500 kg DGVW	Red and yellow retro-reflective	As specified	Not required on slurry tankers, spreaders, chaser bins and similar
Side reflective markings	Yes if over 3,500 kg DGVW and the combination is over 10 m	Retro-reflective	Both sides	Same exemptions as rear markings
“LONG VEHICLE” marking	Yes if over 3,500 kg DGVW and the combination is over 13 m	As specified	1 at the rear	Same exemptions as rear markings
Rear retro reflectors	Fit and keep clean	Red	2	Trailer reflectors are normally the triangular type
Side retro reflectors	Recommended on long trailers	Amber (rearmost may be red)	2 or more each side	Spread along the body
Reversing lamps	No	White	Not more than 2	Only lit while reversing

Rear lamps

Rear lamps are the 2 red tail lights that show the trailer’s presence and width from behind. Every agricultural trailer needs them. Since 1 January 2016 the full trailer lighting system must be fitted and working, not just switched on during lighting-up hours (half an hour after sunset to half an hour before sunrise). The only exception is for older trailers (pre-1980, or 30+ years old according to current RSA guidance) used only in daylight, and any lights fitted to those must still work.

Fit the lamps at the rear corners, as close to the outer edge as the body allows, so drivers behind can judge the trailer’s width. On trailers with high bodies and wide flared sides, a lamp board or a second pair of lamps placed where they can be seen helps. The tail lamps must be clean and unobscured. Browse our rear lamps for combination tail, stop and indicator units in bulb and LED.

Stop lamps on agricultural trailers

Stop lamps are obligatory on agricultural trailers in Ireland. This is one of the clearest differences from older advice, which often treated trailer brake lights as optional. A trailer usually hides the tractor’s own stop lamps, so drivers behind depend on the trailer lamps to know when the combination is braking.

Stop lamps must be red and come on when the tractor’s service brake is applied. They are normally combined with the tail lamp in a single rear cluster using a P21/5W (380) twin-filament bulb or an LED equivalent. RSA guidance is to replace lamps like-for-like with type-approved units showing an E or e mark.

Direction indicators and hazard lamps

Direction indicators are required on agricultural trailers and interchangeable towed equipment. Fit 1 amber rear indicator on each side, approved as a Category 2 lamp (the approval mark has a 2, 2a or 2b above it).

The indicators should sit near the outer edges and flash in phase with the tractor’s indicators on the same side, from one switch. The driver must be able to tell from the seat that the indicators are working, which in practice means a tell-tale that also covers the trailer’s indicators. When the tractor’s hazard switch is on, the trailer’s indicators should flash too.

Trailer indicators add load to the tractor’s flasher circuit. Older thermal or electronic flasher units sized for the tractor alone may flash too fast or not at all with a trailer connected, and LED lamp boards can cause the opposite problem. See trailer lights not working for the fault-finding steps.

Rear reflectors and reflective markings

Rear reflectors are red, and on trailers they are normally triangular. The approval mark on a triangular trailer reflector includes “III” or “IIIA”, which is the triangular class. Triangular rear reflectors are meant for trailers, so do not fit them to the tractor itself.

Heavier trailers also need retro-reflective markings. Under S.I. 249/2014, agricultural trailers over 3,500 kg design gross vehicle weight need rear reflective markings, side reflective markings when the combination is over 10 m, and a rear “LONG VEHICLE” marking when the combination is over 13 m. The RSA says these markings do not apply to towed equipment that can carry more than 3 times its own unladen weight, such as slurry tankers, fertiliser or manure spreaders and grain chaser bins. Replacement triangles and amber side reflectors are in our vehicle reflectors range.

Side lamps at the front

Side lamps (front position lamps) are on the obligatory list for agricultural trailers. They are white, face forward, and should sit near the outer edges of the trailer’s front corners. The front corners are the part an oncoming driver is most likely to misjudge, especially when the trailer is wider than the tractor.

The Irish rules allow only white or yellow light to the front, so do not fit amber or red lamps facing forward on the trailer.

Side marker lamps and side reflectors

A side marker lamp is required on the trailer when the tractor and trailer combination is over 10 m long. The RSA page describes this as “a marker lamp on the right-hand side”. Trailers made on or after 1 January 2016 must use UN/ECE-compliant marker lamps and markings. If you want to be sure of the exact position for your trailer, check the RSA’s Revised Standards for Agricultural Vehicles guidance.

Many farmers fit marker lamps on both sides of a long trailer, which helps at night on narrow county roads and at junctions. Side marker lamps are amber. Amber side reflectors spread along the body add a cheap extra layer of visibility. Our side marker lamps suit long bale trailers and low loaders.

Number plate and number plate lighting

Agricultural trailers must have number plate lighting, which the 1963 Regulations call “identification mark lighting”. Using a trailer not equipped with the prescribed lamps and identification mark lighting carries a €60 fixed charge.

The detailed rules on which plate an agricultural trailer displays were not confirmed for this guide. General practice is for the trailer to show the towing tractor’s registration, but check with Revenue, which handles vehicle registration, if you are unsure. The plate lamp is wired with the tail lamps so the plate lights whenever the side lamps are on. Dust and water ingress are the usual reasons a plate lamp fails, and sealed LED plate lamps are the common replacement.

Lighting boards for towed equipment

Towed equipment without its own lights, such as balers, sprayers, rakes and similar machines, needs lights only if it hides the tractor’s own front or rear lamps or reflectors. In that case a lighting board must be fitted (S.I. 249/2014). A lighting board carries the rear lamps, stop lamps, indicators and number plate lighting on a single panel that clips or straps to the back of the implement.

Rear fog lamps and reversing lamps

A rear fog lamp is not on the obligatory list for agricultural trailers. If one is fitted, it must be red and should only be used in dense fog or falling snow, which is the Rules of the Road test in Ireland. Switch it off when visibility improves.

Reversing lamps are optional. Not more than 2 may be fitted, white or yellow, and they may only be lit while reversing. On a 7-pin 12N connection there is no reversing circuit, so trailer reversing lamps need a 12S or 13-pin connection or a separate feed.

Wide, long and heavy agricultural trailers

Size changes the picture in 4 ways:

1. Beacon: every agricultural tractor must have a flashing amber beacon switched on whenever it is on a public road. The legal requirement is on the tractor, not the trailer. A high-sided trailer can block a cab beacon from behind, so a second beacon on the trailer is a sensible addition.
2. Width limits: the RSA sets a maximum width of 2.55 m for an agricultural trailer and for a tractor and trailer combination. Flotation tyres and mudguards may protrude up to 100 mm each side beyond the 2.55 m limit.
3. Length: an agricultural trailer may be up to 12 m long, and a tractor and trailer combination up to 18.75 m. Remember the lighting thresholds at 10 m (side marker lamp, side reflective markings) and 13 m (“LONG VEHICLE” marking).
4. Weight: unplated combinations may not tow more than 3 times the tractor’s unladen weight. Plated trailers follow the weights on their authorisation plate.

Loads that overhang the back of the trailer need marking. The Rules of the Road says loads overhanging the rear by more than 1 m must carry a red flag or cloth at least 300 mm square by day, and a red reflector and red light at night. Side projections must show white to the front and red to the rear at night. The 1963 Regulations also require projecting load lamps for longer overhangs during lighting-up hours.

7-pin and 13-pin trailer connectors

The trailer lights connect to the tractor through a 7-pin or 13-pin plug and socket. Most tractors and farm trailers in Ireland use the 7-pin 12N connector (ISO 1724), which carries left and right indicators, left and right tail lamps, stop lamps, earth and one auxiliary pin that is normally used for the rear fog lamp. The pin layout, cable colours and wiring steps are in our 7-pin trailer plug wiring guide.

The 13-pin connector (ISO 11446) carries all the 12N lighting functions plus reversing lamps, a permanent feed and an ignition feed in one plug. It is standard on cars, vans and pickups, and some farm vehicles and trailers now use it. A 13-pin to 7-pin adapter connects one to the other for the lighting functions. See 13-pin trailer plug wiring for the pinout and adapters. Some 24V machines use the 24N connector (ISO 1185), which has a different pin layout, so 12V and 24V plugs and lamps should never be mixed.

Roadside checks and common trailer lighting failures

Agricultural trailers that are not commercial trailers do not need a periodic roadworthiness test, but they must be kept roadworthy. Their lights are checked at the roadside by the Gardaí, and RSA Vehicle Inspectors also carry out roadside checks, often jointly with Gardaí. The lamps must be clean and working at all times, including in daylight.

The most common failures found on farm trailers are:

• A bad earth at the plug, the lamp board or the trailer chassis, which causes dim, flickering or crossed-over lights.
• Corroded pins in the 7-pin plug or socket, from water, slurry and road salt.
• Cable chafed through where it runs along the drawbar or over the headboard.
• Cracked lenses and missing triangular rear reflectors.
• A number plate lamp that has filled with dust or water.
• Indicators that work on the tractor but not on the trailer because of a failed flasher or blown fuse on the trailer circuit.

Using a trailer not equipped with the prescribed lamps and identification mark lighting, or without a required marker lamp, carries a €60 fixed charge. A defect that makes the combination dangerous can be dealt with more seriously in court. Gardaí have stopped tractors towing slurry tankers at night with no lights, and proceedings followed.

A pre-season trailer lighting check

A 10-minute check before harvest, silage or slurry season catches most faults before they cause a stop on the road:

1. Connect the trailer and switch on the side lamps. Walk round and check both tail lamps, both front side lamps, any marker lamps and the number plate lamp.
2. Have someone press the brake and check both stop lamps.
3. Run the left indicator, the right indicator and the hazards, and confirm the trailer lamps flash in time with the tractor’s.
4. Check every reflector and reflective marking is present, clean and the right colour: red at the rear, amber at the sides.
5. Open the plug, clean the pins with contact cleaner and a fine brush, and smear the contacts with dielectric grease.
6. Follow the cable from the plug to the lamp boards and replace any section that is chafed, cut or held on with tape.

Frequently asked questions

Does an agricultural trailer need brake lights?

Yes. Since 1 January 2016, agricultural trailers and interchangeable towed equipment in Ireland must have stop lamps, along with side lamps, rear lamps, direction indicators and number plate lighting (S.I. 249/2014). The trailer hides the tractor’s stop lamps, so working trailer brake lights matter for everyone behind you.

Does a farm trailer need indicators?

Yes. Direction indicators are on the obligatory list for agricultural trailers. Fit 1 amber Category 2 indicator on each side at the rear, flashing in phase with the tractor. The only exception is for older trailers used only in daylight.

When does a trailer need side marker lamps or side markings?

A side marker lamp is needed on the trailer when the tractor and trailer combination is over 10 m long. Trailers over 3,500 kg design gross vehicle weight also need side reflective markings when the combination is over 10 m, unless they are equipment such as slurry tankers, spreaders or chaser bins that can carry more than 3 times their own unladen weight.

What number plate goes on a tractor trailer?

General practice is for the trailer to display the towing tractor’s registration, but the detailed rule for agricultural trailers was not confirmed for this guide, so check with Revenue. Whatever plate is carried, the trailer must have number plate lighting.

Why do my trailer lights work on one side only?

The usual cause is a poor earth, either at pin 3 of the plug or where a lamp board earths to the trailer frame. A damaged core in the cable, a corroded pin or a blown fuse on the tractor’s trailer circuit can also take out one side. Our trailer fault guide walks through the tests in order.