Stopping distances — Rule 126, the two-second gap and chevron markers

“How far back is far enough?” has two official answers, and they are not the same number. One is a distance — the overall stopping distance for your speed, which is what the theory test asks you to recite. The other is a time — the two-second gap, which is what you can actually judge from the driving seat at 70 mph. Rule 126 gives you both, and knowing which one a question is asking for is half the answer.

Rule 126 in full

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

That first sentence is the rule the rest hangs off, and it applies everywhere — not just to the car in front. A blind bend, a crest, a fog bank and a parked van all shorten the distance you can see to be clear, and the speed has to come down to match.

For the vehicle ahead, Rule 126 sets a floor:

leave enough space between you and the vehicle in front so that you can pull up safely if it suddenly slows down or stops. The safe rule is never to get closer than the overall stopping distance

allow at least a two-second gap between you and the vehicle in front on high-speed roads and in tunnels where visibility is reduced. The gap should be at least doubled on wet roads and up to ten times greater on icy roads

remember, large vehicles and motorcycles need a greater distance to stop. If driving a large vehicle in a tunnel, you should allow a four-second gap between you and the vehicle in front

And one figure people forget until a tunnel sign reminds them: if you have to stop in a tunnel, leave at least a 5-metre gap between you and the vehicle in front.

The table you have to know

Overall stopping distance is two separate things added together. Thinking distance is the ground you cover between seeing the hazard and the brakes starting to bite. Braking distance is the ground you cover once they do. Only the second one is about the car; the first is about you.

The car-length column uses the official average of 4 metres (13 feet) per car, and it is the column worth picturing. Doubling your speed from 30 to 60 mph does not double the distance — it takes you from six car lengths to eighteen. Thinking distance rises in a straight line with speed; braking distance rises much faster, which is why the gap between the two columns keeps widening down the table.

Memory tricks for reconstructing those numbers under exam pressure — thinking distance in feet, and the half-step multiplier ladder — are in the mnemonics guide.

Is the printed table a best case?

The figures are published with their own caveat attached, and it is a short one.

The distances shown are a general guide. The distance will depend on your attention (thinking distance), the road surface, the weather conditions and the condition of your vehicle at the time.

Four variables, and only one of them is the car. A driver who is tired, distracted or looking at a phone stretches the thinking column. A polished, wet, greasy or icy surface stretches the braking column. Worn tyres and tired brakes stretch it again. The table describes an alert driver on a dry road in a vehicle in good condition — which is why Rule 126 words it as a floor you never go below rather than a target to aim at.

For the theory test, the printed figures are the answer. On the road, they are the best case.

Distance or time — Rule 126 gives you both

The two instructions in Rule 126 are not the same size, and it is worth knowing which one you are using.

• The overall stopping distance is the safe rule: never get closer than it. At 70 mph that is 96 metres.
• The two-second gap is the minimum on high-speed roads. Two seconds at 70 mph is roughly 63 metres of road.

So a two-second gap is the floor, not the ideal, and a driver sitting exactly two seconds behind on a dry motorway is still inside the published stopping distance. The reason the Code offers it at all is practical: nobody can judge 96 metres by eye at speed, and everybody can count.

The counting method is fixed. Pick a stationary object at the roadside — a sign, a bridge, a marker post. When the vehicle in front passes it, start counting. If you reach the object before you finish, you are too close. The traditional two-second phrase is “only a fool breaks the two-second rule”, which takes about two seconds to say at a normal speaking pace.

Because it is a time and not a distance, one count works at every speed: the faster you go, the more metres those two seconds buy you. What the count does not do is keep pace with the table. Braking distance grows faster than speed does, so the two figures cross over at around 40 mph — below that, two seconds is more road than the overall stopping distance; above it, steadily less. On a motorway the gap has to be opened up beyond the count, not measured by it.

Wet, ice and fog change the answer

The multipliers are the part of this topic the theory test asks about most, and they are stated as rules in their own right.

In wet weather, stopping distances will be at least double those required for stopping on dry roads.

The reason given is grip: the tyres have less of it. Rule 227 also asks you to keep well back from the vehicle in front so you can see and plan further ahead, and warns that rain and spray make it harder to see and be seen.

keep well back from the road user in front as stopping distances can be ten times greater than on dry roads

Ten times. At 70 mph that is most of a kilometre, which is really an instruction to drive far slower rather than to leave 960 metres — Rule 231 fills that in: slow speed, as high a gear as possible, gentle acceleration and braking, and braking progressively on the straight before a bend rather than in it.

Fog is a visibility problem rather than a grip problem, and Rule 235 answers it with the same first principle as Rule 126 — be able to pull up well within the distance you can see clearly:

keep a safe distance behind the vehicle in front. Rear lights can give a false sense of security

On motorways the same instruction is repeated in the motorway rules, because that is where the consequences are worst. Rule 260 asks you to keep a safe distance from the vehicle in front and increase the gap on wet or icy roads, or in fog.

Chevron markers: the gap, painted on the road

Some stretches of motorway take the guesswork out entirely by painting the gap on the carriageway.

Some motorways may have special chevron markings in the centre of the traffic lanes. These are spaced 40 metres apart, and keeping 2 marks between your vehicle and the one in front will provide a safe driving distance at 70 mph. There will be signs advising you to check your distance, keep 2 chevrons apart and keep your distance.

Three things follow from that, and it is worth being precise about which are stated and which are not.

• The spacing is 40 metres. Two intervals of chevrons is therefore 80 metres of road, in the same territory as the 96-metre overall stopping distance at 70 mph.
• The instruction is to keep two marks between you and the vehicle in front, at 70 mph. It is a countable target, which is the whole point: two painted shapes are easy to see, a hundred metres of tarmac is not.
• No time is attached to them. The chevrons measure distance, the same quantity as Rule 126’s overall stopping distance; the two-second gap in that same rule measures time instead. They are two different tools for the same job, and converting one into the other is not something the marking claims to do.

Not to be confused with chevron hatched areas

A different marking shares the name, and mixing them up costs marks in the test.

Areas of white diagonal stripes or chevrons painted on the road. These are to separate traffic lanes or to protect traffic turning right.

Those are areas at the side of or between lanes, bounded by white lines: if the border is broken you should not enter unless it is necessary and safe, and if the area is marked with chevrons and bordered by solid white lines you MUST NOT enter it except in an emergency. The vehicle-spacing chevrons are something else — repeated marks along the centre of the running lane that you drive straight over. Rule 130 covers the hatched areas in full.

Tailgating, and the two things not to do about it

Rule 126 names the behaviour and defines it.

Tailgating is where the gap between you and the vehicle in front is too small for you to be able to stop safely if the vehicle in front suddenly brakes.

Tailgating is dangerous, intimidating and can cause collisions, especially when driving at speed. Keeping a safe distance from the vehicle in front gives you time to react and stop if necessary. Dangerous and careless driving offences, such as tailgating, are enforced by the police.

Driving without due care and attention, or without reasonable consideration for other persons using the road, is an offence under section 3 of the Road Traffic Act 1988 — and the wording covers driving without reasonable consideration for other road users, not only driving without due care.

Two responses come up constantly and the Code rules out both.

Slowing down to teach them a lesson. Rule 168 covers being overtaken and reads across directly: maintain a steady course and speed — slowing down if necessary to let the vehicle pass — never obstruct drivers who wish to pass, and understand that speeding up or driving unpredictably while someone is trying to get past is dangerous. Easing off to help somebody by is exactly what the rule asks for; a punitive brake-check is the opposite of it. Rule 169 adds that you should not hold up a long queue of traffic and should pull in where it is safe to let it pass.

Speeding up to shake them off. Rule 235 says it outright for fog and the logic holds everywhere: do not accelerate to get away from a vehicle which is too close behind you.

What the Code does back is easing off gently to open up more space in front of you, so that if the vehicle ahead stops hard you can bleed off speed rather than stamping on the brakes with somebody’s bonnet in your mirror. And when someone finally does overtake and drops into the gap you were keeping, Rule 168 tells you what to do next:

Drop back to maintain a two-second gap if someone overtakes and pulls into the gap in front of you.

Rebuilding the gap is the rule, not an optional courtesy.

Common test questions and the answers

“What is the typical overall stopping distance at 60 mph?”

73 metres (240 feet), or about eighteen car lengths — 18 metres of thinking and 55 metres of braking.

“In good conditions, what is the typical shortest stopping distance at 70 mph?”

96 metres (315 feet), about twenty-four car lengths.

“How much longer will it take to stop on a wet road?”

At least twice as far. Rule 227 puts wet stopping distances at least double the dry figures because the tyres have less grip.

“What about ice or snow?”

Stopping distances can be ten times greater than on dry roads (Rule 230), and Rule 126 uses the same multiplier for the time gap.

“What is the minimum gap on a high-speed road?”

At least two seconds, doubled to at least four on wet roads, and up to ten times greater on icy roads.

“You are driving a large vehicle through a tunnel. What gap should you allow?”

Four seconds. And if you have to stop in a tunnel, leave at least a 5-metre gap.

“What do chevron markings in the middle of a motorway lane mean?”

They are vehicle-spacing markings, spaced 40 metres apart. Keep two marks between you and the vehicle in front at 70 mph.

“A vehicle overtakes you and pulls into the gap you were leaving. What should you do?”

Drop back to rebuild a two-second gap (Rule 168). Do not speed up, and do not close the gap.

Where this shows up in revision

Stopping distances, weather multipliers and following gaps sit in the Safety margins revision topic, and they turn up again in Hazard awareness and Motorway rules — a hazard you spot early is one you can deal with using the gap you already had. Work the 14 DVSA topics, read Rules 126, 130, 168, 227, 230, 235 and 260 in the Highway Code, 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 126, 130)
• GOV.UK — The Highway Code: Typical stopping distances (PDF) — the Rule 126 diagram, thinking/braking split and car-length figures
• GOV.UK — Highway Code: driving in adverse weather conditions (Rules 227, 230, 231, 235)
• GOV.UK — Highway Code: using the road (Rules 168, 169)
• GOV.UK — Highway Code: motorways (Rule 260)
• GOV.UK — Know your traffic signs: motorway signs, signals and road markings — chevron vehicle-spacing markings
• legislation.gov.uk — Road Traffic Act 1988, section 3 (careless, and inconsiderate, driving)

Highway Code and Know your traffic signs excerpts are reproduced under the Open Government Licence v3.0.