Everything You Need To Know About Stopping Distances

Knowing your vehicle’s stopping distance is an important part of passing your driving test, but it’s also something that can be all too quickly forgotten in our day-to-day driving. In fact, tailgating – not allowing enough stopping distance to the car in front – is one of the biggest causes of road accidents in the UK. So, whether you’re studying for your theory test or revising the rules of the road, we’re here to help.

What is stopping distance?

In simple terms, stopping distance is the time that it takes to bring a moving vehicle to a complete stop. This includes the time it takes to realise the hazard, react to it and the vehicle coming to a complete stop. 

Stopping distance = thinking distance + braking distance

What is the 2-second rule?

The 2-second rule is a quick and practical way of checking your stopping distance when you are travelling in your car. It is a rough guide and you should allow a greater distance when travelling at faster speeds or in bad weather conditions. 

Here’s how it works:

1. When travelling choose a fixed point e.g. a lamppost, road sign or flyover
2. Watch when the vehicle in front passes the fixed point
3. Then say “only a fool breaks the two second rule” or count for 2 seconds
4. If you haven’t passed the fixed point before saying the above, you’re probably keeping a good stopping distance. 

What can affect stopping distance?

Stopping distance is determined by more than just speed and in truth, there are many factors that influence the stopping distance of a vehicle. They can broadly be put into three categories: driver awareness, vehicle condition and environmental factors. We take a look at each in more detail below:

1. Driver Awareness
   Tiredness: Driving tired can severely affect reaction time as well as your attention and awareness regarding what’s happening on the roads. The longer you take to react the further your stopping distance is going to be. It’s therefore recommended that you take a break every 2 hours on long journeys.Distractions: Whether it’s in-car tech, talking to passengers or fiddling with the heating, it can be all too easy to become distracted when driving. Distractions can quickly lead to a lack of focus on the road leading to increased stopping distances and a greater risk of accidents.

   Stress and Emotions: Stress and pressure are a common part of our busy lives but they can have a big impact on our driving. Whether you’re running late, desperate to get home after a long day at work or experiencing a case of road rage. Feelings of stress and pressure can lead to higher speeds, shorter separation gaps and slower reaction times.

   Drink and Drugs: It goes without saying that you shouldn’t drink and drive, and it is also illegal to drive under the influence of certain drugs. Why? Because consuming alcohol and drugs increases the time it takes to process information such as hazards on the roads and therefore increases your stopping distance.

2. Vehicle Condition
   Brakes: Not surprisingly the condition of your car’s brakes will affect its braking distance; so keeping them in good working order is important. You may find it takes longer than usual for your brakes to slow your car down if they are becoming worn or have been poorly fitted. It’s also worth noting that cars fitted with ABS will encounter little difference in terms of stopping distance. ABS is designed to give more control to the driver in an emergency brake situation rather than stopping the vehicle quicker.Tyres: Worn or incorrectly-inflated tyres negatively affect your car’s stopping distance. Older tyres, with a reduced tread (less than 3mm) will have a greater stopping distance than newer tyres with a deeper tread (8-7mm). This is because worn tyres have much less grip on the road. Overinflated tyres also result in less road grip, so it’s important to regularly check the condition of your tyres.

   Vehicle size and weight: Larger and heavier vehicles have a longer braking distance than smaller, lighter vehicles. Why? It’s all to do with physics and the fact that more force is required to stop a heavier vehicle.

3. Environment
   Road Conditions: Be aware that spillages, and damaged or muddy roads can also increase stopping distance. In fact, any poor-quality surface that reduces the friction between your tyres and the road is inevitably going to have a negative effect on your braking.Weather: It goes without saying that bad weather conditions like rain, snow and ice can make a huge impact on a vehicle’s stopping distance. In wintery conditions, snow can become compacted in the tyre tread which greatly reduces the effectiveness of the tyres and their grip on the road. This can lead to sliding and stopping distances up to 10 times greater than on a dry road. Check out our tips on driving in ice and snow page for more helpful guidance on driving in the winter.

   Field of vision: How far and clearly a driver can see also has a significant impact on stopping distance. Fog, for example, can massively impact your field of vision, giving you less time to respond to the hazard or vehicle stopping in front of you.

   Other road users: Whilst you cannot control the actions of other road users it’s important to allow for a ‘margin-of-error’ in your driving, to avoid a rear-end shunt from the vehicle behind. Allowing plenty of space in front, behind and to the left and right of your vehicle should prevent any accidents. If you feel you’re being tailgated simply pull over safely and let the vehicle pass.