Speed contributes to your stopping distance when braking suddenly, and the severity of impact should a crash occur. The faster you go, the harder you hit.
In 2020, 43% of fatalities on our roads were speed related crashes.
47% of fatalities were on 110km/h zones, followed by 14% IN 80km/h zones and 12% in 50km/h zones.
Physics of speed
Reaction and stopping distance
The speed you’re travelling at affects your reaction time and stopping distance if you need to brake or manoeuvre suddenly. That’s the distance you travel by the time you react, and the distance you travel once you brake.
But that’s not the only factor – driver and road environment also play a part.
For example, a distracted or tired driver will take longer to react, and wet road conditions will make a car travel further when braking.
On a dry road, an average family car driving at 70km/h will travel 29+ metres before reacting and an additional 27+ meters before coming to a complete stop. On a wet road, the same car, at the same speed will travel an extra 13 metres.
Collision impact
If you're in a crash, your speed determines the force of impact you experience when you collide. So, an impact at 80km/h will be far more forceful than an impact at 50km/h.
Survival Speed
Vehicles don’t have to be going fast to cause harm. Many fatalities occur at lower speeds, especially when pedestrians or bike riders are involved.
A person walking has a 90% chance of survival if hit at 30km/h, but only 60% chance of survival if hit at 40km/h. The human body has a limited chance of surviving an impact above 80km/h.
Selecting a speed
Responsible drivers and riders select the appropriate speed to travel for the conditions around them. So, if driving conditions change, it’s up to you to adjust your speed accordingly, within that limit. Speed choices are influenced by a number of factors:
- The road and vehicle conditions such as road layout, surface quality (e.g., unsealed road), wet/icy roads, vehicle condition/age
- The traffic environment, such as the speed of other road users, or bumper-to-bumper traffic density
- Weather conditions such as heavy rain, fog, sun glare, all cause low visibility
Remember, the speed limit is the maximum speed allowed, it’s not the goal. Responsible drivers and riders select the appropriate speed to travel for the conditions around them.
If you’re a motorcyclist, think carefully about the roads and the speed limits that are safe for you to ride on. Just like driving any vehicle, you can put yourself and other road users in danger if you ignore these factors.
For more information on speed, visit our Speeding page.
