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What are the correct stopping distances?

22nd February 2019

The shorter the stopping distance, the safer you are

Stopping distances – sound familiar? You might recall them from your driving lessons (admittedly, a long time ago for some). It has something to do with when you apply the brakes, right? Kind of. If you’re not 100% sure what stopping distances actually are, it’s worth a recap, and appreciating that the tyres fitted to your car – as well as the prevailing weather and temperature – significantly influence the length of this distance. This guide will help you understand the difference between stopping distance, braking distance and how weather conditions can affect stopping distances of vehicles.

So, what is stopping distance?

Many drivers believe – mistakenly – that it is simply the distance a vehicle travels from the moment the brakes are applied to when it finally comes to a stop. In fact, this is a description of ‘braking distance’. While certainly a large component of stopping distance, it’s not the only one. Before this value can even be considered, there’s an equally important factor to take into account – thinking distance.

Starting to sound familiar? Your thinking distance is the amount of road travelled that it takes you to determine that you even need to brake, and to subsequently do so. This reaction time can seem relatively short – perhaps just a second or two – but even this amount can result in a vehicle travelling – in relation to the circumstances of needing to brake – a very long way. This is especially true when driving at high speed, such as when on a motorway.

The importance of stopping distances cannot be underestimated. Only this month, Highways England has revealed that in 2016 more than 100 people were killed following 1,896 accidents attributed to tailgating – driving far too close to the vehicle in front – because of a lack of sufficient stopping distance to avoid collision. Remember, your stopping distance equals thinking distance plus braking distance.

What are the factors that determine stopping distances?

There are many. Thinking distance can be influenced by the speed of your vehicle, prevailing weather conditions, your visibility, whether or not you are tired, your sobriety, and both internal and external distractions. It’s reasonable to presume that a sober, alert, undistracted driver, with clear visibility, and driving at a reasonable speed will have quicker reaction times compared to a driver who is weary, distracted, and under the influence of alcohol or drugs, while driving excessively fast in wet, windy conditions.

Braking distance is also influenced by the speed of your vehicle, and the prevailing weather conditions, and the tyres fitted to your vehicle (specifically the condition they’re in, the seasonal type, and quality of the compound). It goes without saying that travelling at high speed –particularly in poor driving weather – requires a longer braking distance to come to a full stop, compared to a vehicle travelling at a slower speed on a clear, sunny day.

But what about the tyres fitted to your car? Exactly how much of a role do they actually play?

Your tyres can make all the difference when it comes to stopping distances

It’s a fact. Tyres are a massive factor in determining your stopping distances, particularly in poor driving conditions – such as when it’s raining, or snowing, and in low temperatures. The impact of these conditions will be minimised or exacerbated by the condition and quality of your tyres, as well as the type of seasonal tyres you have fitted to your vehicle. Tyres are that important, and can be the difference between avoiding a collision, or having one. Let’s look at these factors.

Tyres in good condition help provide shorter stopping distances

The condition of your tyres will significantly determine your ability to brake effectively. Vital factors include tyre pressures, tyre damage, and tyre tread depth.

Your tyre tread depth significantly determines just how much water can be efficiently cleared from between your tyres and the road surface. Deeper tyre tread depth results in more being removed quickly and effectively. Conversely, tyres that have a lower level of tread depth typically struggle to remove water as efficiently. This matters because it’s the rate of removal that dictates just how much grip your tyres have. Enduring less grip is dangerous, the result of which is taking longer to come to come to a full stop. The more tread depth your tyres have, the greater their grip will be – and the shorter your stopping distances.

In Britain, the road legal minimum tread depth is only 1.6 mm, but experts – including Merityre and leading premium tyre manufacturer, Continental – strongly recommend that the tyres fitted to your vehicle have at least 3 mm of tread depth. Why? Because time and time again, independent braking distance tests conclusively demonstrate that on wet roads it can take up to two full car lengths further to come to a stop with just 1.6 mm of tread, compared to tyres that have 3 mm.

Think about that. Two car lengths is a significant distance, especially when you’re trying to stop at high speed, or in poor visibility. It could be the difference between avoiding a collision, or having one. As we highlighted earlier, with tailgating seemingly more prevalent on UK roads, there’s an increased chance of being involved in being injured – or worse – through a shortage of stopping distance.

Tyre tread depth matters – it’s a vital factor in determining your final stopping distance. But it’s not the only one…

Why are there are different tyres for different seasons?

Are you aware that there are different tyres for different seasons? Not all motorists are. In the UK, the overwhelming majority of motorists fit ‘summer tyres’ on their vehicles, all year round. It’s why, for example, Continental’s award winning ContiPremiumContact™ 5 tyre is popular across a range of vehicle segments, including compacts, estates, saloons, SUVs and 4x4s. On the European mainland it’s a different story. Many of our continental cousins choose to switch to ‘winter tyres’ after the dry, hot summer season. But why?

Primarily because there’s a misconception amongst many British drivers that winter tyres are only needed for driving in snowy conditions, and that – since we don’t typically get much snow in the UK – there isn’t a real need to switch tyres. Never has a tyre related myth been so wrong. It’s true that winter tyres do actually perform better than summer tyres on snowy roads, but that’s not the main reason that Europeans fit them. Their real motivation is the drop in temperature.

A set of winter tyres will surpass the performance of summer equivalents at the point the temperature drops down to 7°C, and below. At this point, in a like for like performance comparison, stopping distances are significantly shorter for vehicles fitted with winter tyres, versus those running on summer tyres.

How much shorter? Again, independent tyre tests and research conclusively shows that it can be as much as two car lengths in distance. That’s a long way to travel in cold, often wet, snowy, or icy conditions, when you’re desperately trying to avoid a collision with another road user, or worse, a pedestrian.

Why do winter tyres perform so much better at 7°C and below?

Simple. It’s because of the different type of compounds they’re made with. Summer and winter tyres are manufactured from different combinations of materials. Each combination is designed to perform optimally at the appropriate temperature. It’s like how summer clothing and winter clothing are made from different fabrics and material weights, right?

Summer tyre compounds rigidify and become less flexible at temperatures of 7°C and below, and, as a result, offer much less suppleness and grip than winter tyres – which are specifically engineered to thrive at this temperature range. In contrast, winter tyres – with their much softer compounds – aren’t designed to cope with the warmer temperatures above 7°C, the point at which they become comparatively sticky and sluggish – which leads to poor rolling resistance, increased tyre wear, and which is a big drain on fuel, too.

And what about Mertiyre all season tyres? Surely, as their name suggests, these relatively new tyres offer the best of both worlds, right? Not quite. To better understand what an all season tyre is, you need to appreciate just what considerations go into making a tyre. The process is a delicate balance act, determining which of the main characteristics of performance, safety, comfort, and economy are most important. Different tyre manufacturers will put a different emphasis on each one, depending on the driver type and vehicle segment they’re engineering it for.

There’s only so far you can mix a compound before a natural bias towards one characteristic outweighs the qualities of others. As such, ultimately – at its core – the all season tyre is a compromise on the optimal characteristics of dedicated summer and winter tyres. Yes, all seasons offer a good spectrum of warm and cold temperature characteristics typically found on separate tyres, but for this very reason it can never match the optimal performance levels of its specialist stablemates in a single tyre – including when it comes to delivering shorter stopping distances in wet conditions – whether it be warm or cold temperatures. That said, Continental’s AllSeasonContact™ tyre offers a great balance of summer and winter driving attributes, and is ideal for drivers who want a good tyre for all year round usage.

Unsure about stopping distances? Talk to the experts at Merityre

At Merityre, our number one priority is ensuring that our customers in South-East England have the very best tyres fitted to their vehicles. We have over twenty fast-fit centres located across the region, all staffed by experienced, expert tyre professionals. If you’re unsure about stopping distances, and how to reduce yours, talk to us today. We can offer you with impartial, expert advice, and provide you with the best fitting solution.

Find your nearest Merityre fast-fit centre.