Three-Second Gap: How Do I Do It and Is It Really Necessary?

4 minute read

One of the first things new drivers learn about is the three-second gap. So what exactly is this gap, why is this gap needed and is it really necessary? Let’s have a look.

What is a three-second gap?

The three-second gap is the amount of time it’ll take before your vehicle reaches the vehicle in front of you at any speed. When travelling at 60km/h, this is around 50 metres which averages to around 10 car lengths¹.

Across the world, a two to four-second gap is generally encouraged in good driving conditions. In Australia, the three-second gap is widely recommended and is a rule of thumb to keep a safe distance from the car in front of you. This allows you, as the driver, to safely stop in the case that the car in front suddenly brakes – ultimately avoiding a rear-end collision. Although it may seem like a natural reaction, in order to suddenly stop, the driver will react, hit the brakes and then the car will have to come to a complete stop. These three steps can take much longer than you would think.

This rule, as mentioned, applies when driving in good conditions meaning that a four-second rule is generally more appropriate when driving in conditions that are ‘not good’. These conditions can be rainy weather as well as late nights and early mornings where it can be dark or foggy.

Road conditions can also affect the amount of space you should put between the car in front of you. Driving on rural or unpaved roads can increase the difficulty and time it takes to come to a complete stop in comparison to the time it takes on paved roads.

NSW Government² encourages drivers to keep a five-second gap when driving at higher speeds, as speed affects the distance needed to stop safely. Put simply, the faster a car is going, the longer it will take the car to come to a complete stop.

Why can it be difficult to maintain a three-second gap?

As most things are, keeping a three-second gap can be easier said than done. Driving on busy roads or during peak hours in cities can make it more difficult to maintain a three-second gap. There might be pressures to ‘keep up with the speed’, aggressive tailgating and drivers may slip into your three-second gap.

How can I maintain a three-second gap?

One way the South Australian government³ recommends checking whether you are keeping the appropriate gap between the car in front of you when on the road, is this.

1. Check that the car in front of you has passed a stationary object, for example this can be a utility pole or rubbish bin.
2. Count the number of seconds before you reach that same object.
3. If you counted three seconds, then you’re generally keeping a safe distance but if you counted anything under three seconds then you’re not allowing a safe distance.
4. If you were under three seconds, slow down, make sure you’re not going over the speed limit and give it another go.

Alternatively, you can do the above observation as a pedestrian on the sidewalk. As a Learner driver, this can give you a better visualisation of the actual distance you should keep between the car in front of you when driving.

While it is recommended to maintain a three-second gap, if this is not possible then keeping the biggest possible gap is the next best step.

Is a three-second gap really necessary?

Car insurance provider, AAMI, revealed in their annual road safety report⁴ that nose-to-tail crashes were the most common across all Australian states except for South Australia, Tasmania and the Northern Territory. In Tasmania and the Northern Territory, the most common crash type was hitting a stationary object or vehicle. Data from 2021⁵ shows that carparks were also a common place for collisions. While there is no further data, carparks are generally not the best environment to encourage a safe three-second gap as they are usually quite packed and not spacious enough.

So, is a three-second gap necessary? To allow yourself sufficient time to react and avoid a crash, yes.