What affects your stopping distance?

Whether it’s due to a hazard in the road or the car in front stopping sharply, most drivers will have to perform an emergency braking manoeuvre at least once in their time on the road. When it happens, you’re going to want the car to stop in the shortest distance possible to avoid an accident.

Your stopping distance is made up of two factors. Thinking distance, which is the time that it takes your brain to process information and react, and braking distance, which is the length you travel from pressing the brake pedal to the car coming to a complete stop.

There are several elements that can impact both of these factors, which are worth taking into consideration to achieve an optimal stopping distance. Here are some of the things that can have an effect on how fast your car can stop; as well as what measures you can take to reduce your stopping distance.

Tyre Pressure

Your tyres can have a huge impact on your stopping distance, so there are several things to look out for when it comes to your tyres - tyre pressure is one of them. By having the correct tyre pressure, your car has an ideal amount of contact with the road, providing ample control and traction. However, when tyres are over or under-inflated, the amount of contact between tyre and road is reduced.

Underinflated tyres make more contact with the road on the outer edges of the tyre, whereas overinflated tyres make more contact in the centre.

Both types of incorrect pressure cause irregular wear of your tyres, and reduce their traction. This means your tyres are less effective at biting into the road surface and bringing the car to a halt. By doing a tyre pressure check every month and using the recommended pressure, you can better maintain your tyres and their ability to stop the vehicle. If you’re unsure about if your tyre pressure is correct, check out our “What should my tyre pressure be?” blog.

Tyre Wear

Another thing to consider regarding your tyres is tread depth. Legally, your tyres need to be changed when the tread depth reaches 1.6mm. However, the tread depth on your tyres can have a massive impact on your braking distance long before you reach the minimum. Most tyres start with 8mm of tyre tread, which gradually wears away with use. As the tread reduces, so does the tyre’s ability to grip the road.

At 30mph on a wet road, a car with brand new tyres will come to a stop in 25.9 metres. The same car travelling in the same conditions with tyres with a tread depth of just 3mm would come to a stop in 35 metres. That’s 35% further, despite the tyres still being perfectly legal. When the tyres reach the minimum of 1.6mm of tread, the stopping distance increases to 43 metres. That’s almost double the stopping distance of the new tyres!

Tyre Quality

You’ll also want to consider the overall quality of tyres when thinking about improving your stopping distance.

Buying premium tyres provides peace of mind that you are buying a quality product, which is why many opt for brands like Goodyear, Michelin and Pirelli, associating them with excellent performance.

This is with good reason, as countless tyre tests show that premium tyres really are worth the cost due to their high performance, particularly compared to their cheaper competitors, as well as the control, grip and stopping distance they offer. When travelling at 60mph, a car with premium tyres could stop as much as 16 metres shorter than a set of budget tyres. Premium tyres have other proven benefits, including increased fuel efficiency, lifespan and aquaplaning resistance.

Speed

Your speed is one of the only factors that impacts both your thinking distance and braking distance. It’s no surprise that the faster you’re going, the longer the distance you travel before you apply the brakes, and before your car comes to a complete stop.

For example, at a speed of 20 mph, you typically travel 6 metres before you make the decision to brake. With braking distance at this speed, it takes another 6 metres to come to a halt; that’s an average of 12 metres to come to a complete stop. With every 10mph above this, your thinking distance increases by 3 metres. Combine that with the braking distance and you’ve got a long way to go before stopping.

Once you reach 70mph on the motorway, your car can take an average of 75 metres to come to a stop. Combined with your thinking distance of 21 metres, that’s 96 metres, or the length of 24 cars, to come to a stop. In the event of an emergency, this can result in a crash or an accident. Aim to keep your distance from the car in front of you and keep an eye on your speed, as this could be the difference between safely stopping and an accident.

Brakes

Having properly maintained brakes is something that can make a big difference to your stopping distance. Brake pads have a block of friction material that pushes against the brake disc when the brakes are applied. This material wears down over time, and the brake disc can become grooved - causing your brakes to overheat and lose stopping power. By ensuring that your brakes are well maintained, you can prevent this loss of stopping power, which ultimately reduces your stopping distance - as well as not having to shell out for a brake replacement.

It’s important to remember that brakes can also be affected by wet roads and standing water, leading to moisture between the pads and discs which can make them less effective. If you have driven through deep water, make sure you pump the brake pedal a few times while driving slowly and safely to dry them out and ensure they work when you need them.

Road Conditions

Unlike other elements, the weather is something that we, unfortunately, have no control over. Road conditions like standing water, ice and snow can have a huge impact on your stopping distance, as any slippery surface that reduces the friction between your tyres and the road is inevitably going to have an effect on your braking.

In heavy rain, aquaplaning can occur where the tyres cannot disperse the water between the tread and the road surface quickly enough, leading to a loss of control. 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 10 times greater than on a dry road. The best defence when driving in bad weather is to keep your distance and take it slow.

View of the Road

Visibility doesn’t directly affect your braking distance, but it can inhibit your thinking distance. The longer it takes for you to spot hazards in the road, the more time passes before you hit the brake pedal. A dirty windscreen will reduce your view of the road, so remember to keep it clean and make sure your windscreen wipers are working properly.

Damaged wiper blades can reduce your visibility even further by smearing dirt across your windscreen, so make sure you replace any damaged parts immediately. On cold, frosty mornings get out there a few minutes early to warm the car up and scrape all the ice off to make sure you set off with a clear windscreen.

An Altered Mental State

Typically, an altered mental state would be considered driving under the influence of alcohol or drugs, as this increases the time it takes for you to process information. A driver who is under the influence of drink or drugs could take a few extra vital seconds to spot a hazard, which could lead to a fatal accident. Driving under the influence is illegal, with penalties such as a minimum 12-month driving ban, an unlimited fine and up to six months in prison.

While driving under the influence is something that should be avoided at all costs, this is not the only dangerous form of altered mental state. Driving when tired can be just as dangerous, with as many as one fifth of accidents on monotonous roads like motorways thought to be caused by drivers falling asleep at the wheel. Even if you don’t drop off behind the wheel, being tired is also something that severely slows your reaction time and impairs your decision making ability.

If you notice yourself getting tired or losing concentration while driving, make sure you find somewhere safe to stop and take a break. Taking 15-minute breaks every two hours on long journeys and sharing driving duties when possible can give you the best chance of staying alert and optimising your stopping distance.

Want to keep your car in top form?

To achieve the best possible stopping distance, ensuring that your car is performing at its best is crucial. If your car is due a service, or you’d like to err on the side of caution, you can choose from a range of our car servicing options to keep everything working smoothly.

To book in for a car service, please get in touch with your local Kwik Fit centre today, or book online.