Relative Risk or Absolute Risk? Why You Should Care

This article is about the difference between what’s known as ‘relative risk’ versus ‘absolute risk’ and why you need to know the difference. Understanding how to use these ideas is important in a world where often people don’t worry about real and meaningful risks, and often fret about things that almost certainly will never harm them. 
  
When I tune my guitar, I can use relative tuning, or absolute tuning. If I tune my guitar with the correct tonal distance (measured in hertz or the number of vibrations per second) between say the A string and the E string, they are in tune, relatively speaking. When I wind all the strings to the tension necessary to produce the correct tonal distance between them, I can play the guitar and it will sound in tune. BUT, only if I am playing alone. If I want to play with other musicians, I need to use absolute tuning.

When I need to play with other musicians and instruments, it’s critically important that we all set our instruments to the exact frequencies for each note. For example, ‘concert tuning’ means that the A note is generated at 110 hertz. If I’m using relative tuning with my A string tuned to say 95 hertz, we won’t be playing in concert, and the result will be awful to listen to; even though individually we might be in tune (relatively).

Driving is a lot like this. If I always drove on roads by myself, I could do a lot of things that alone were not a problem, and would only affect me if I got it wrong. But when I need to drive ‘in concert’ with others, we need to be working together measuring risks accurately to prevent crashes that could easily be avoided if we were all ‘in tune’ with one another.  

Here are a couple of examples of relative risk.

1. A passenger positioned in the front seat of a car is about 7 times more likely to die in a crash than a passenger seated in the rear seat.
2. Driving with a Blood Alcohol Content (BAC) of .05% makes the driver about 7 times more like to crash than with a BAC of 0.0%.

Now these real risks are only meaningful if the absolute risk of fatality in a road crash is similarly real and meaningful; and it is.

Here are some examples of absolute risk.

1. The most likely cause of accidental death in Australia (that is not disease or violent crime etc.) is as the result of a road accident.
2. The next most likely cause of accidental death in Australia is as the result of a slip, trip or fall.

For these reasons, I’m particularly careful when I drive, climb or use a ladder etc. When I take my grandchildren in my car, I make sure they sit in the back even though they are old enough to legally travel in the front.   

Now Motorcyclists are around 37 times more likely to be injured or killed in a traffic crash than a car driver/passenger. When I ride, which I do regularly, both the relative risk and the absolute risk are both real and meaningful to me. I put all of my available resources into avoiding a crash and optimizing my safety.

Worrying about flying on a large commercial airliner over a long distance, is not necessary, because the absolute risk of dying in a commercial airliner is so low it is considered ‘risk de minimis’ that is to say, it is very, very, safe indeed and the chance of fatality is almost zero. Now the relative risk between the survivability of an airliner crash by sitting in the front versus the rear of the plane could be calculated, but it’s a moot point, because the absolute risk is so low.
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What’s the main message here? The risks associated with being in an injury or fatality producing motor vehicle crash are both real and meaningful at a personal level.

The good news is there is a lot that you can do to reduce your risk of being injured or killed in a car crash to that something like the airliner example above ‘risk de minimis’.

BUT you need to allocate a lot of personal resources, planning, attention and certain proactive behaviours to manage the risks. Accurate risk assessment triggers this personal expenditure and can definitely help. 

If you’d like to know more about these topics, how to apply them to your personal driving, or perhaps across your team, please call or email me. Cheers Jeremy