As fun as driving can be, and as necessary as it may be in many of the country’s decidedly car-centric urban areas, driving is not a particularly safe activity. Even with modern cars having far more safety features and safer structural designs – as shown in the Insurance Institute for Highway Safety’s crash testing pitting a ’90s Chevy Blazer against a modern Blazer crossover – more than 2.25 million people are injured in car crashes each year. Every day, about 100 people die in traffic accidents, with more than 36,600 deaths expected in 2025 alone.
While not everything is under your control as a driver, there are proven ways to make your commute safer, giving you the best opportunity to react safely if something dangerous happens on the road. Chief among these is the three second rule. No, this is not a suggestion that everyone should drive a three-second 0 to 60 car. Rather, the three-second rule, first coined by the National Safety Council, urges drivers to always maintain at least a three-second gap between their car and the car in front of them.
To comply with this rule, drivers must identify a fixed landmark, such as a tree, a road sign, or an intersection, and begin counting down to the moment when the rear of the car in front of them passes this landmark. If you don’t take even three seconds for the front of your car to pass the same landmark, you are probably following too closely and may increase the risk of a collision if the car in front of you brakes suddenly. It is important to maintain this distance both in the city and on the highway for safety and it is good to maintain a consistent practice.
Why not time and distance?
According to the NSC and highway engineers, it may seem unusual to measure following distances in terms of seconds instead of feet, but it’s the best way to make sure you’re staying at a safe distance. This is because the most important thing in maintaining a safe driving distance is not how far away you are, but how much time you have to react to changing conditions. One reason why spatial distances are not sufficient here is that the time taken to reach a complete stop depends on how fast you are going.
For example, a car traveling at 30 mph requires about 150 feet of speed to come to a complete stop after applying the brakes. But at 70 mph, that distance is about 500 feet. It is not possible or efficient to calculate many different safe following distances based on the probable speed of the car and then ask drivers to remember these distances and adjust as their speed changes. There are a lot of steps and a lot of margin for error. Similarly, not everyone is skilled enough at estimating distances to correctly judge when they are appropriately far away.
When you need to make a quick stop during an emergency, a few things are in order, and each takes precious time. First, you have to realize that there is an emergency, and then you have to respond by stepping on the brake pedal. This usually takes 1.5 seconds or more. It takes you at most 1.5 seconds to safely come to a complete stop. These measures are actually independent of how fast you are moving, which is why time and not distance is the gold standard for calculating safe following distance.
3 seconds is the baseline, not the bottom line
Although the three-second rule is a good rule of thumb, it is not the be-all and end-all of safe following distances. The three-second rule is designed to provide proper following distance during ideal driving conditions, but many factors can increase the ideal time between you and the nearest car in front of you. NCS recommends adding one second to your count for each complicating factor or condition that makes your trip less safe.
Factors that are guaranteed to add extra seconds to your next distance include illness, stress, fatigue, weather, and vehicle size. If you’re feeling cool and energetic but feeling snowed in, add one second to your follow time, for a total of four seconds. If it’s raining and you’re tired, add two seconds, for a total of five. If it’s raining at night and you’re driving a large SUV while suffering from a migraine, add four seconds. Or even better, stay home if you’re in that kind of situation. This is probably what the sleeping Tesla driver, who caused the FSD failure with sunglasses, should have done.
Basically, anything that can reduce your reaction and reaction time, you should keep a long distance from it. In Australia, it’s legal to drive with a little medicinal THC in your system, but you should probably add a second for that, too, as cannabis is known to slow reaction times. However, at the end of the day, it is up to you to use your best judgment and stay safe on the roads. When in doubt, give the driver in front of you a little extra room, because you never know what’s going to happen.
