Cycling fatalities with motor vehicles

Photo by Pixabay on Pexels.com

Gravel riding, mountain bike riding, and cycling on separated bike paths – far from a road – are relatively safe. Injuries are possible but fatalities unlikely. Cyclists have much greater risks riding on roads. Collisions with a motor vehicle are more likely to be fatal. This is the story of what makes motor vehicles so deadly.

The problem is discussed in a report from Austroads: “Integrating Safe System with Movement and Place for Vulnerable Road Users” (2020). Vulnerable road users are typically cyclists and pedestrians. People are soft but motor vehicles are not. When we see photos of a bike that is bent from the impact, we do not need to picture what the cyclist looked like.

The problem of energy

Motor vehicles at speed carry an enormous amount of energy and its destructive power can be seen when two cars collide. The energy in a collision with a cyclist is mostly determined by the speed of the motor vehicle. Double the speed of the motor vehicle and the energy increases four times. Small increases in speed result in large increases in energy. The opposite is also true. Small reductions in road speed greatly reduce the motor vehicle energy and with it any fatalities. This is why motor vehicle speed reduction is the most effective and inexpensive measure to improve road safety, as many European countries have already realised.

Any speed increase will result in a much greater increase in the energy of the motor vehicle. Motor vehicle energy and the relationship to speed.

The relationship between the speed of the motor vehicle and energy is unfortunate. The probability of cyclist fatality for a collision with a car travelling at 50km/h is almost certain. The good news is that by reducing the speed of the car to 30km/h, a cyclist will almost certainly survive, yet injuries are still very likely.

Relationship between collision speed and the probability of a fatality. Source: Integrating Safe System with Movement and Place for Vulnerable Road Users (Austroads,2020)
Relationship between collision speed and the probability of a fatality. Source: Integrating Safe System with Movement and Place for Vulnerable Road Users (Austroads,2020)

The problem of braking

Most drivers would remember the discussion of breaking distance from driving school. Stopping distances greatly increase with speed, and again this is due to the energy relationship. The problem is made far worse when we consider human reaction times. The time it takes us to recognise danger is painfully long and nothing we can do will shorten it (unless you are a professional F1 driver). Authorities heed drivers to pay attention and not get distracted by other things such as our phones but even with the best intentions, our concentration will lapse. In half of all fatal bike cycle accidents, the driver never manages to brake! This is why decreasing road speed limits make such a big difference in the case of a collision with a cyclist.

Below is the stopping distances of typical passenger cars for a range of initial travel speeds from the Austroads report. A car travelling 50km/h will take 30m to stop but moved forward over 20m before the driver has starts to brake.

Stopping distances of typical passenger cars for a range of initial travel speeds (calculations assume a coefficient of friction of 0.70 and a driver perception-reaction time of 1.2 seconds). Source: Integrating Safe System with Movement and Place for Vulnerable Road Users (Austroads,2020)
Stopping distances of typical passenger cars for a range of initial travel speeds (calculations assume a coefficient of friction of 0.70 and a driver perception-reaction time of 1.2 seconds). Source: Integrating Safe System with Movement and Place for Vulnerable Road Users (Austroads,2020)

So, what can we cyclists do to help change our car and speed loving culture? Here are a few ideas:

😊 Slow down when you pass a cyclist to set a good example. Emotions are contagious!

😊 Educate your family and friends about the risk of them driving too fast around cyclists.

😊 Use your lights and wear high vis bike clothing to make it easier for drivers to spot you.

Photo by Pixabay on Pexels.com

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