Tailgating is the cause of just over 33% of all car crashes in the U.S. and 76% of crashes for drivers with 6 or less years of experience. One of the reasons these numbers are so high is we’re often taught to follow too close! Many of us learned “1 car length per 10 MPH” …WELL THAT’S WRONG!  

The math just doesn’t work, at 10 MPH maybe 1 car length is enough, but at 50 MPH 5 car lengths is nowhere near enough. 1 car length per 10 MPH of speed creates a linear relationship with stopping space and speed. The relationship between our speed and our ability to stop however is much more exponential than linear, not to mention our human need to pause to think and react, which takes time as well. 

Humans take time to react to events that they aren’t expecting. Response time varies greatly across different tasks and even within the same task under different conditions. It can range from .15 second to many seconds depending on whether you’re reacting to something you’re expecting or not, or if there is a clear cut response given a situation. In accident recreation sciences they use 1.5 seconds as an average driver's reaction time, but our research has found that 1 second to react is common for most people. With an average human reaction time the ability to actually stop is drastically increased as the braking doesn’t begin until we’ve actually reacted. 

In Control recommends that you leave 3 seconds between your car and the vehicle you’re traveling behind.  

When the rear of the car in front of you passes some inanimate object (sign, tree, etc) you should be able to count out “one one thousand,” “two one thousand,” “three one thousand,” before the front of your car should be passing that same object. 

At night, consider even more space—always adjust for the conditions. Lengthen that following distance even more if it’s rainy, snowy, you’re in a huge, heavy vehicle, etc.

Once you’ve practiced the 3 second rule for a while you shouldn’t need to count each and every time there is a car in front of you. But taking the time every now and then to check that time is a great idea to keep you safe!

Other factors that impact your ability to stop:

1. Weather - In poor weather conditions, a car’s total stopping distance is likely to be longer for a number of reasons. For starters, poor visibility might mean the driver takes longer to react—increasing their thinking/reaction distance. But slippery roads caused by rain, snow, or ice will also extend the total braking distance. Research suggests braking distances can be doubled in wet conditions – and multiplied by 10 on snow or ice. That means, in the snow, it could take you further than the length of seven football fields to stop from 65mph.

2. Road conditions - It’s not always as obvious as ‘bad weather equals longer stopping distances’, either. A road might be particularly greasy if there has been rain after a period of hot weather, or if oil has been spilled on it. Be prepared for black ice on cold days, and watch out for loose surfaces such as gravel. These things could make it difficult to stop in a hurry.

3. Driver condition - While all these factors can affect the braking distance, the individual behind the wheel is ultimately responsible for the thinking/reacting distance – and that can have a huge effect on the overall stopping distance. A driver’s age, how awake they are, and if they’re under the influence of any drugs or alcohol can all influence how quickly it takes them to react. Using a mobile phone rather than concentrating on the road can have devastating effects on a driver’s stopping distance – just a few seconds glancing at your phone can add a football pitch to your overall stopping distance at motorway speeds. If the traffic ahead has stopped, that could ruin your day very quickly. Other distractions in the car— such as loud music and passengers—can also affect the amount of thinking time before you apply the brakes.

4. Car condition - A vehicle's condition can also have an impact on your ability to stop. For example, cars equipped with poorly designed tires can take an extra 45ft to stop from 65mph in wet conditions compared to tires with exceptional ratings for wet conditions. Research has also found that tires at the legal limit of 2/32’s of an inch of tread can need an extra 60% more road to stop compared to brand new tires. Under-inflated tires will also have an impact on stopping distances, as will cars with poorly maintained brakes. Check your brake pads to make sure they have plenty of life left in them, and test your brakes after driving through water to check for moisture left between the pads and discs.