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What is stopping distance?
Stopping distance is the total space your car needs to come to a complete stop once you’ve spotted a hazard. It’s a combination of how quickly you react and how effectively your car can brake, and is made up of:
- Thinking distance: the ground you cover while your brain processes what’s happening and your foot moves to the brake pedal.
- Braking distance: the distance it takes your car to come to a halt once the car brakes are applied.
If you’ve ever wondered how to calculate stopping distance, the Highway Code has provided standard figures. These figures apply to dry roads and assume that your car is in good condition with well-maintained tyres and brakes. They’re a helpful baseline, but in real life, the distance you actually need may be longer if weather conditions are poor, the road surface is slippery, or your tyres are worn — which is why knowing how to check your tread depth is so important.
- 20mph: 12 metres (around 3 car lengths)
- 30mph: 23 metres (around 5 car lengths)
- 40mph: 36 metres (around 8 car lengths)
- 50mph: 53 metres (around 12 car lengths)
- 60mph: 73 metres (around 17 car lengths)
- 70mph: 96 metres (around 22 car lengths)
These figures show just how quickly the distance can increase alongside your speed. Even in built-up areas, like towns, you need more space than many people realise.
On faster roads, the gap becomes much larger. Factor in bad weather or worn tyres, and the distance you need can grow significantly, which is why leaving enough room is so important in all conditions.
The two-second rule
It’s hard to picture stopping distances in metres when you’re on the road, so National Highways suggest using time instead. On faster roads, they recommend leaving at least two seconds between you and the vehicle in front when it’s dry. If it's raining, you should double it to four seconds, and if it's icy or snowy, you should leave as much as ten times the normal gap.
To check this, pick a fixed point at the side of the road, such as a lamppost or a road sign. When the vehicle in front passes it, start counting to two. If you reach the marker before you finish, it means you’re following too close. In the rain, you should be able to count to at least four before you reach the same point.
Because you’re counting time rather than distance, this method works whatever speed you’re doing. It’s a quick and simple way to check whether you’ve given yourself enough room to stop safely if something changes up ahead.
But while the rule is easy to follow, our analysis of government data suggests that two seconds isn’t always enough on faster roads…
Are UK drivers really leaving enough space?
The Highway Code’s two-second rule is designed to make judging safe gaps simple. However, our analysis found that in 2024, one in four cars were still travelling less than two seconds behind the vehicle in front, meaning a quarter of drivers are leaving less than the minimum safe gap for dry conditions.
Why two seconds isn’t always enough
When we converted the Highway Code’s stopping distances into time, we found that the two-second rule only really works at lower speeds.
At 30mph, the recommended stopping distance of 23 metres works out at about 1.7 seconds, so leaving two seconds gives you a small margin. But as speeds increase, the gap you need grows much faster than most drivers realise.
At 60mph, the recommended stopping distance is 73 metres, which requires a gap of 2.7 seconds, not two, and at 70mph, the Highway Code recommends a stopping distance of 96 metres, which works out to just over 3 seconds to achieve.
Here’s how the Highway Code’s stopping distances look when converted into seconds:
- 20mph: 1.3 seconds
- 30mph: 1.7 seconds
- 40mph: 2.0 seconds
- 50mph: 2.4 seconds (2 seconds leaves you 0.4s short)
- 60mph: 2.7 seconds (2 seconds leaves you 0.7s short)
- 70mph: 3.1 seconds (2 seconds leaves you 1.1s short)
This proves the two-second rule leaves drivers exposed at higher speeds. Drivers may think they’ve left enough room, but they’re often over a second short of the space needed to stop safely.
What happens at real motorway and road speeds
The shortfall becomes even clearer when we compare stopping distances with how people actually drive in their day-to-day lives. Using government free-flow data, we found that motorway traffic averages 68mph.
At that speed, a two-second gap leaves just 61.1 metres of space between you and the car in front, but the Highway Code recommends 96 metres in dry conditions, leaving drivers 34.9 metres (1.14 seconds) short.
Instead, you’d need to leave at least 3.1 seconds between you and the car in front to stop safely.
In wet weather, the gap is even larger. We found that a four-second gap would give you 122.2 metres of stopping distance, but the Code recommends 171 metres, leaving a shortfall of 48.8 metres (1.60 seconds) — almost the same length as an Olympic swimming pool. To meet the recommended stopping distance, you’d actually need 5.6 seconds to stop safely.
On single carriageways with a 60mph speed limit, the average speed is 51mph. At that speed, two seconds leaves 45.3 metres of space compared with the Highway Code’s 73 metres, a shortfall of 27.7 metres (1.22 seconds). Even in wet weather, a four-second gap covers 90.6 metres, which is still 37.4 metres (1.65 seconds) short of the 128 metres required.
Lower-speed roads look safer on paper, because at 20mph and 30mph the two- and four-second rules do match the Highway Code’s dry stopping distances. But our analysis shows that, in 30mph zones, 43% of drivers speed, and in 20mph areas, that figure rises to 76%. So even where the two- and four-second rules appear to work in practice, speeding quickly erodes the safety margin.
The impact of speeding patterns
Our analysis of hourly speeding patterns shows that drivers are also most likely to go over the limit at times when the roads are quieter.
In 30mph zones, the early hours are the worst. At 5am, 72% of drivers are speeding. On motorways, the highest levels of speeding happen before dawn (4am-6am) and again after the evening rush (7pm-9pm), when 47% of cars are travelling faster than 70mph.
The same pattern shows up across weekends and nights. In 30mph areas, speeding at night is more than 20 percentage points higher than in the daytime. On single carriageways, it rises by about 15 points, and even on motorways — where drivers are generally more compliant — the difference is still measurable at 2 points.
With more drivers travelling faster at these times, the shortfalls we highlighted earlier become even greater, making safe gaps harder to achieve and putting more drivers at risk.
What the casualty data shows us
The figures on time gaps and speeding are worrying enough, but do they actually lead to crashes? Police records suggest they do. Both speeding and following too close appear year after year as contributory factors in collisions, and both continue to cause thousands of casualties on Britain’s roads.
Speeding vs following too close
Our analysis of the latest police collision data shows that in 2023, crashes where “exceeding the speed limit” was a factor led to 7,757 casualties. By comparison, collisions where drivers were judged to be “following too close” caused 4,157 casualties. That makes speeding the larger problem nationwide, but following too close is far from minor, it’s still linked to thousands of people being injured every year.
Where the risks are highest
While it is a widespread problem, the risks aren’t the same across the country. When we compared regional casualty data against the national average, we found that in the West Midlands, around 15% of all casualties involved speeding, compared with the national average of 8.6%, making it the highest in the country.
The West Midlands also has the highest casualty rate per capita, with 16 people per 100,000 injured each year from collisions caused by speeding, followed by the South East (14 per 100,000), Yorkshire and The Humber (14 per 100,000), and London (13 per 100,000).
For following too close, the East of England had the highest share, with 8% of casualties linked to following too close, against the national figure of 4.9%. But looking per capita, the highest risk region is actually the South West (11 per 100,000), followed by the East of England (10 per 100,000).
At the other end of the scale, our analysis found that Scotland is safer than most, with only 5% of casualties involving speeding (5 per 100,000), and 3% linked to following too close (2 per 100,000).
Where risks are rising fastest
Looking at year-on-year change highlights where the problem is getting worse. For speeding, the sharpest increase was in Yorkshire and the Humber, where casualties rose by 15% in 2023 compared with the year before. The South West saw the second biggest increase (12%), followed by the East of England (5%). By contrast, London recorded the biggest fall (-13%) in casualties, followed by the West Midlands (-12%) and the North West (-10%).
For following too close, the North East saw the biggest increase, with casualties up 24% year-on-year. This is followed by Wales with a 20% increase and the South West with a 12% increase. At the other end of the scale, London saw the biggest decline (-17%), followed by the East of England (-15%) and the East Midlands (-14%).
These figures show that while speeding and following too close are risks across the country, local driving habits and conditions can make the problem worse in some regions.
How to keep a safe distance in all conditions
The Highway Code’s advice on stopping distances is meant as a minimum, but our analysis shows that many drivers aren’t leaving enough room, especially at higher speeds or when the weather takes a turn.
Keeping your car in good condition through regular servicing is just as important as the gap you leave, ensuring your brakes respond properly and your tyres have enough tread. Together with small changes in your driving habits, these steps can add a vital safety margin. Here’s how to judge a safe gap on different road types, and how to adjust when road conditions change.
Road types
Motorways:
At 70mph, the Highway Code recommends a dry stopping distance of 96 metres. But looking at free-flow speed data, we know most motorway drivers average closer to 68mph. At that speed, a two-second gap only gives around 61 metres — more than eight car lengths short of what’s needed. Even in the wet, doubling the gap to four seconds only covers about 122 metres, still leaving nearly 50 metres less than the Code’s recommendation.
To close the gap, aim for at least three seconds in the dry, and five to six seconds in the wet. At night or at weekends, when speeding is more common, add another second on top. Each extra second at the motorway speed limit buys you around 30 metres of extra space, roughly the length of seven or eight cars.
Single carriageways:
On 60mph single carriageways, cars typically travel at about 51mph. At that speed, a two-second gap only gives you 45 metres, while the Highway Code recommends 73 metres. A safer margin is two and a half seconds in the dry, and at least four seconds in the wet.
Town driving:
At 20mph and 30mph, the two- and four-second rules do line up with the Highway Code’s stopping distances, but only if you stick to the speed limits. In practice, many don’t. Around 43% of drivers speed in 30mph zones, and in 20mph areas it’s as high as 76%. Even creeping slightly over the limit stretches the distance you need to stop, which means the two- or four-second rules might not be enough. Leaving an extra second wherever possible is a simple way to protect yourself and others.
Weather conditions
Stopping distances can change dramatically depending on the weather. The Highway Code’s stopping distance recommendations are based on dry roads, but once surfaces become wet, icy, snowy, or visibility drops, the space you need can rise sharply. Here’s how different conditions affect how much room you should leave:
Driving in the rain
Wet roads reduce tyre grip and roughly double braking distance. With rain falling on UK roads 44.9% of the year, this is a common risk occurrence that drivers need to be prepared for.
The Highway Code advises doubling your gap in the rain, so if you’d normally leave two seconds in the dry, you should leave at least four. On faster roads like motorways, our research found that even four seconds may still leave you short, so five to six seconds is safer.
Driving on ice
Ice is one of the most dangerous surfaces to drive on. Stopping distances can be up to ten times longer than on dry roads, and traction can disappear without warning.
If the road looks icy, slow right down and leave a gap that feels excessive. Avoid harsh braking or sharp steering, as even small inputs can cause you to lose traction.
Driving in the snow
Snow brings many of the same problems as ice, but with the added risk of reduced visibility from snowfall. It’s always worth brushing up on safe winter driving so you’re ready when temperatures drop.
Cars ahead may lose traction suddenly, so increase the distance between you and the car in front as much as possible and brake gently to avoid locking your wheels. On snowy roads, there is no such thing as leaving too much space
Driving in fog
Fog reduces visibility, which in turn lengthens your reaction time, as you can’t brake for a hazard until you’ve seen it.
Keep your speed down, use dipped headlights or fog lights if visibility is below 100 metres, and leave a larger gap than usual. Even if the road surface is dry, the delay in spotting hazards means you’ll need extra space to react safely.
