Most motorists know the Two Second Rule, which suggests that if there are two seconds of clear road between you and the car in front, you should be able to complete an emergency stop. This forms an important part of any learner driver’s theory test.

But it’s not that simple. There are also other conditions that will affect your vehicle’s stopping distance – that is, the distance travelled between when the decision to stop is made and the vehicle actually coming to a halt.

Here are five of the main factors that can influence your stopping distance.

1. Speed

Speed is the main factor usually considered and is what determines the Highway Code braking distance. Your brakes can only decelerate your car by a certain amount per second, so the faster you’re going, the longer it takes to stop.

Because of this, the typical stopping distance at 70mph is 96 metres, while the stopping distance at 50mph is 53 metres, little more than half as much. The stopping distance at 30mph is just 23 metres, about six car lengths.

2. Reaction

The overall stopping distance formula considers two different things: the braking distance and the thinking distance.

The braking distance is the distance it takes to stop once the brakes are applied.

The thinking distance, however, is the distance between the driver realising they need to brake and when they actually brake.

The thinking distance is calculated at 3 metres for every 10mph. So, thinking distance at 30mph is 9 metres, at 70mph it is 21 metres, and so on.

It’s worth bearing in mind, though, that your individual reactions might be different. As such, it’s important to stay alert while driving so you can get on the brakes quickly in an emergency.

3. Tread

The rule of thumb for minimum legal tread depth is if you insert a 20p coin into the tread of your tyre, it should cover it past the outer border of the coin’s design.

But remember, that is the bare minimum tread depth you need to have across 100% of your tyre’s central zone – any flat spots, cracks or bulges and you should get the tyre replaced immediately.

If your tyre shows any such signs of damage or is already below the minimum legal tread depth, our mobile tyre fitting service is a great option. We can come and replace your tyres at home or work without you having to take to the public roads in an unroadworthy state.

4. Weather

Bad weather can affect your tyres’ ability to grip the road, leading to an increase in overall stopping distance. This can be worsened further by poor visibility, making reaction speeds slower.

Stopping distances in rain can be much longer than on a dry road. In fact, research suggests braking distances are doubled in such conditions. Wet weather poses other hazards too, such as aquaplaning (when your tyre’s tread becomes completely waterlogged and you skid across the surface like ice).

Wet brakes can be less effective, so on rainy days you should use them lightly and regularly, so they dry out.

5. Snow and Ice

Wintry weather is even more dangerous than wet roads, and the total braking distance on ice can be so far that the only safe course of action is to drive much more slowly. For snowy and icy conditions, you can expect your braking distance to be multiplied by 10 – five times greater than in rain.

You can improve your grip on snow and ice by fitting winter tyres to your vehicle, as these have a special tread pattern designed to work better on slippery surfaces.

Our seasonal refit service switches you from summer to winter tyres as colder weather approaches. We can also switch your tyres back to summer tyres in the spring too.

How to remember stopping distances

Although the exact braking distance depends on the condition of your tyres, brake pads, and the road conditions, it’s useful to know how to remember stopping distances.

For speeds up to 40mph, subtract one from the first digit and multiply by 12 – this gives a total stopping distance (including thinking/reaction time) of 12 metres at 20mph, 24 metres at 30mph and 36 metres at 40mph.

Officially, it’s 23 metres at 30mph, not 24, but if you mostly do urban driving, it’s a good rule of thumb.

Faster speeds start to require a longer distance to stop. At 50mph, for instance, it’s 53 metres, but by 70mph it’s 96 metres, equivalent to 24 standard car lengths.

At these speeds, it’s difficult to judge distance precisely, so use the Two Second Rule instead. If you’re on a motorway, look out for chevrons printed on the carriageway to help you keep the right distance from the car in front.

You might not know that cats’ eyes are usually spaced at 18 metre intervals, so at motorway speeds you should keep at least five cats’ eyes between you and the car in front.

Ultimately, it’s driving experience that helps you to ‘read’ the road and slow down or leave more space when necessary, combined with healthy brakes and good tyres that deliver grip when you need it most.