Dazzled by oncoming headlights — what the Highway Code tells you to do

Every winter the same argument runs: one side says braking for oncoming headlights is itself dangerous, the other says it is the only sane response to being unable to see. The Highway Code does not leave it open. Rule 115 gives one instruction for the moment you are dazzled, and it is a single line — slow down, and if necessary stop. Everything else in this guide is either the reasoning behind that line or the separate rules about not becoming the person causing it.

slow down, and if necessary stop, if you are dazzled by oncoming headlights

That is the third of three bullets under Rule 115. The first two are about not creating the problem yourself — use dipped headlights, or dim-dip if fitted, at night in built-up areas and in dull daytime weather so that you can be seen, and keep your headlights dipped when overtaking until you are level with the other vehicle before changing to main beam if necessary, unless that would dazzle oncoming road users.

Note the wording of the whole rule: You should also, not MUST. Rule 115 is advice, which is why it carries no Law line — the difference between the two forms, and why an advisory rule still counts in court, is worked through in MUST vs should.

Why slowing down is the answer and not the risk

The objection is always the same: brake for oncoming lights on a dark road and the driver behind runs into you. It is worth taking seriously, and it is also the wrong reading of what Rule 115 asks for. The rule does not say brake. It says slow down — and it sits directly underneath the rule that explains why.

Stopping distances. Drive at a speed that will allow you to stop well within the distance you can see to be clear.

Read those two rules together and the logic closes. Being dazzled shortens the distance you can see to be clear, sometimes to a few metres. Rule 126 ties your speed to that distance. So when the distance collapses, the speed has to come down with it or you are, by the Code’s own standard, driving too fast — not because a number changed, but because your sight did.

Rule 125 says the same thing from the other end. The speed limit is the absolute maximum and does not mean it is safe to drive at that speed irrespective of conditions, and among the situations it names for reducing speed is driving at night, “as it is more difficult to see other road users”. A 60 mph limit on an unlit rural A-road is not an invitation to hold 60 through a wall of glare.

What that means in practice is a decision made early rather than late. Ease off as the lights come towards you, so you arrive at the worst of the dazzle already slow, rather than braking hard in the middle of it. The hard-braking objection describes a driver who reacted at the last moment. Rule 115 describes one who did not have to.

What about the queue behind you?

The Code has a rule for that too, and it is a genuine limit on how far the first instruction goes.

Do not hold up a long queue of traffic, especially if you are driving a large or slow-moving vehicle. Check your mirrors frequently, and if necessary, pull in where it is safe and let traffic pass.

So the answer to “everyone behind me is furious” is not to drive faster than you can see. It is to check your mirrors and, where it is safe, let them go. Rule 169 and Rule 115 point in the same direction: if the road at night is consistently beyond what you can comfortably deal with, the solution is a slower route and a place to pull in, not a faster one.

Do not dazzle back

This is where the advisory rule ends and the law begins. Rule 114 is a MUST NOT, with a Law line naming the lighting regulations.

You MUST NOT use any lights in a way which would dazzle or cause discomfort to other road users, including pedestrians, cyclists and horse riders.

The legislation underneath it is worded as an effect, not a list of situations. In the table of prohibited uses in the Road Vehicles Lighting Regulations 1989, the first prohibited use listed against a headlamp is a single line.

Used so as to cause undue dazzle or discomfort to other persons using the road.

That framing matters more than it looks. Because the test is the effect on the other person, no rule needs to spell out the specific places where main beam becomes a problem — a right-hand bend, a crest, a rise where your beam lifts into oncoming eyes, a queue you are sitting in. If the light lands where it dazzles, the prohibition is engaged, and “they started it” is not a defence to it. Retaliation puts you on the wrong side of a legal requirement in answer to someone else’s breach of that same requirement — two offences instead of one.

Flashing back is a separate mistake with its own rules, and we cover what a headlight flash actually means in flashing headlights and waving out. Reaching for the fog lights is a third: Rule 236 makes their use a MUST NOT unless visibility is seriously reduced, precisely because they dazzle — the full test is in fog lights.

The three dazzle rules, side by side

Two of the three tell you to do exactly the same thing, which is the fastest way to remember any of it. The Code’s answer to glare from in front is always speed, and its answer to glare you are creating is always the lights.

Bright sunlight is the same rule wearing a different hat

Rule 93 is one of the shortest in the book, and it is easy to skip because it sits among the eyesight and alcohol rules rather than the lighting ones.

Slow down, and if necessary stop, if you are dazzled by bright sunlight.

Rule 237, in the hot-weather section, repeats it word for word at the end of a rule about ventilation and soft road surfaces: “If you are dazzled by bright sunlight, slow down and if necessary, stop.” Two chapters apart, same instruction. A low winter sun on a wet road at four in the afternoon is a dazzle question, not a weather question, and it is one of the recurring scenes worth recognising in when to click on hazard perception.

What Rule 94 adds is the thing people reach for and should not.

At night or in poor visibility, do not use tinted glasses, lenses or visors if they restrict your vision.

Tinted lenses sold for night driving do not remove glare; they remove light, all of it, including the light you needed. Sunglasses are the daytime tool. After dark the Code says take them off.

Is it your car, or is it theirs?

There are three sourceable reasons the road genuinely looks worse than it used to, and none of them require guessing.

Headlamp aim. Aim is checked at every MOT, and the inspection manual grades it strictly: an aim outside the laid-down limits, an aim that cannot be tested, or a beam image that is obviously incorrect are each recorded as a major defect. A car whose headlamps sit a fraction too high throws its dipped beam into oncoming eyes at every dip in the road while its own driver notices nothing. If you have changed the springs, carried a heavy load in the boot, or had a front-end repair, the aim is worth checking.

Aftermarket conversion kits. Dropping an HID burner into a housing designed for a halogen filament does not simply make the light brighter — it puts the light in the wrong places. The Department for Transport’s position is unambiguous.

In the Department for Transport’s view it is not legal to sell or use after-market HID lighting kits, for converting conventional Halogen headlamps to HID Xenon. If you want to convert your vehicle to Xenon HID you must purchase completely new Xenon HID headlamps.

The reason given is the beam pattern: because the lens and reflector were engineered around a halogen filament, “there will be glare in some places and not enough light in other places within the beam pattern”. A converted car dazzles and under-lights at the same time. The MOT inspection manual says the same thing from the testing end — an existing halogen unit on a vehicle first used on or after 1 April 1986 must not be converted to HID or LED bulbs, and a tester who finds one has to fail the headlamp.

Your eyes. Sensitivity to glare rises with age and with several ordinary eye conditions, and the standard is not a matter of how you feel about it. Rule 92 sets the floor: you MUST be able to read a vehicle number plate, in good daylight, from 20 metres, and if you need glasses or contact lenses to do it you MUST wear them at all times while driving. Separately, night blindness (nyctalopia) is on DVLA’s list of eye conditions you have to declare, alongside glaucoma, diplopia and retinitis pigmentosa — and you can be fined up to £1,000 for not telling DVLA about a medical condition that affects your driving. If night driving has become materially harder over a couple of years, that is an optician appointment, not a personality trait.

Your own lights, done properly

Two details in Rule 115’s first two bullets are worth pulling out. Dipped beam in dull daytime weather is there so that you can be seen, which is a different job from seeing and the reason the rule applies in conditions that are merely grey rather than dark. And the overtaking permission to go to main beam once you are level with the vehicle you are passing carries its own exception in the same breath — “unless this would dazzle oncoming road users”. The exception is part of the instruction, not a footnote to it.

Underneath both sits Rule 113’s MUST: sidelights and rear registration plate lights lit between sunset and sunrise, headlights at night except on a road with lit street lighting, and headlights whenever visibility is seriously reduced. The Road Vehicles Lighting Regulations put the same duty in statutory form, requiring obligatory dipped-beam headlamps to be kept lit during the hours of darkness other than on a lit restricted road, and in seriously reduced visibility.

One more from Rule 114, easy to miss because it is not about headlamps at all: in stationary queues, apply the parking brake and, once the traffic behind has stopped, take your foot off the footbrake so the brake lights go out. Held brake lights at a red light on a wet night are their own small glare problem, and the Code names it.

Northern Ireland

The Northern Ireland Highway Code runs Rule 115 as three bullets ending on the same instruction — “slow down, and if necessary stop, if dazzled by oncoming headlights” — though its opening bullet is shorter, asking only for dipped headlights in dull daytime weather. Rule 114’s ban on using any lights in a way that would dazzle or cause discomfort is there too. What differs is the citation and the typography: the lighting Law lines point at the Northern Ireland regulations, regulation 30 rather than 27, and one is printed under Rule 115 as well as under the must-not rules; and the Code sets its legal requirements in lower case rather than capitals. Our Northern Ireland theory test guide covers the rest.

How this comes up on the theory test

Dazzle sits in vehicle handling, one of the fourteen DVSA question-bank topics, which covers driving in rain, fog, snow, dark and wind. The distractors are predictable once you know that Rule 115’s answer is always speed.

“Flash your headlights to let the other driver know”

No. Rule 114 makes dazzling other road users a MUST NOT, and a flash aimed at an oncoming windscreen is exactly what it prohibits. It also means something else entirely to the driver receiving it.

“Switch to main beam so you can see past the glare”

The opposite of the answer, and a legal requirement broken to get there. Main beam towards oncoming traffic is the prohibited use in regulation 27, whatever the other driver is doing.

“Speed up so you’re past it sooner”

Rule 126 ties your speed to the distance you can see to be clear. Being dazzled shrinks that distance, so the speed goes down, not up.

“Only slow down if you cannot see anything at all”

Rule 115 does not set a threshold. It says slow down, and if necessary stop — stopping is the escalation, slowing is the default.

“Use your fog lights, they cut through glare”

They do not, and Rule 236 makes using them a MUST NOT unless visibility is seriously reduced, because they dazzle other road users and can obscure your brake lights.

“Wear tinted glasses at night to take the edge off”

Rule 94 says not to use tinted glasses, lenses or visors at night or in poor visibility if they restrict your vision — and a tint that dims the glare dims everything else with it.

Practise it

Read Rules 113 to 116 alongside Rules 92 to 94 on the Highway Code — the lighting rules and the vision rules are written as two halves of one problem and answer each other directly. Then work the DVSA topics, check the terms in the glossary, and sit a full mock theory test under the real timer. It is free to get started.

Sources

• GOV.UK — Highway Code: general rules, techniques and advice for all drivers and riders (Rules 113 to 116, 125, 126)
• GOV.UK — Highway Code: rules for drivers and motorcyclists (Rules 92, 93, 94)
• GOV.UK — Highway Code: driving in adverse weather conditions (Rules 235, 236, 237)
• GOV.UK — Highway Code: using the road (Rule 169)
• legislation.gov.uk — Road Vehicles Lighting Regulations 1989, regulation 27 (restrictions on the use of lamps)
• legislation.gov.uk — Road Vehicles Lighting Regulations 1989, regulation 25 (requirements about the use of headlamps and front fog lamps)
• GOV.UK — MOT inspection manual: cars and passenger vehicles, lamps, reflectors and electrical equipment (sections 4.1.2 headlamp alignment and 4.1.4 compliance with requirements)
• GOV.UK — Aftermarket HID headlamps — Department for Transport
• GOV.UK — Eye conditions and driving
• GOV.UK — Driving eyesight rules
• nidirect — Rules and advice for drivers and riders (103 to 158) — Northern Ireland

Highway Code excerpts are reproduced under the Open Government Licence v3.0.