Speed, Surprise and Space
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This article by Steve Haley originally appeared in the newsletter of the Oxford Institute of Advanced Motorists. We heard about it and immediately sought permission to re-publish it here.

Speed, Surprise and Space
-by Steve Haley

As Advanced Drivers we know some important things that help us to keep safe on the road. We know that safety is the highest priority whenever we are behind the wheel. And we know too that safe driving is mainly in our thinking skills - the decisions we make, well before your hands and feet get the chance to execute them. But if I were to ask any sample of you: "What are the causes of danger on the road?", everyone’s list would be different. And they would include a lot of things you just wish other drivers would not do - things you can't control. 

This article looks at the factors of risk that are common in every driving situation - that you can control. The point is that, if our sense of danger is incomplete, we can never be very safe. Unintended risks will inevitably creep into our routine driving. And we will tend to spot them late, rather than early when they are easier to handle. Let's look at how crashes happen. Every crash needs three things: 

  • something is moving
  • something unexpected happens
  • someone runs out of room. 
Then the impact occurs - it is that simple. Removing any one of them prevents it happening. So there are these three elements to risk, which we can call: Speed, Surprise and Space.

Speed seems easy to understand, though is often taken too much in isolation. There are also important deceptions, such as the “comfort” given by travelling very close other vehicles, because our brain is fooled by the reduced sensation of movement. The question we should ask is: "How well can I change speed or direction to avoid danger?". Braking ability is clearly crucial, especially at higher speeds - but not just in panic mode! And we should not think of braking as our only possible response either.


Surprise is less well understood. The question for us here is: "How certain am I about everything that will happen next?". We can define a surprise as anything that makes someone consider doing something before they can calmly check it is safe. Everything that is not predicted is a potential threat. Having the time to react safely is crucial - not being rushed. Within this there are three types of surprise: those we receive from others, those we give to others, and those we create for our self by being inattentive. All of these create danger for us, and we can combat them in turn with: 

  • good anticipation
  • being predictable
  • paying attention to the task.

Space is partly understood, though most drivers use it badly. The question here is: "How much room do I have available to use?". The idea of "threatened space" is the key to safety. Space can be empty but still dangerous if threatened by someone possibly moving into it. Understanding other road users’ desire for space is crucial. Also important is the very effective technique of "giving space to danger".

Risk model

These elements form a simple yet complete "risk model" for how likely a collision is to occur. Increasing Speed will tend to increase risk, and increasing Surprise will too. But increasing Space decreases risk. So this is easy to remember as:

This works very intuitively out on the road. For example, if space opens up in front of you, and you are confident about what will happen next, then you are happy to go faster, and vice versa. But note that these factors do not individually cause a crash. The problem is when they get out of balance. So that is the key task - to keep Speed, Surprise and Space in balance with each other in every situation.

Personally, I believe that Surprise is the most dangerous of the three. Within reason, I don't mind if someone goes past quickly, or moves about on the road - but if they do something unexpected, that immediately feels threatening. 

The power of this model is in showing, very simply, the things we must always control in our driving. It is also a very practical tool. The 3 factors are easily memorable, and things we can think about together, especially with practice. 

It also helps to explain how studies into the causes of crashes around the world can show conflicting results. Crashes rarely have just one cause, so compiling the figures becomes subjective. We can see too why the "Speed Kills!" campaign is controversial - no single thing is ever enough to control risk. 

Having explained the probability of crashing, we can then think about the safety margin we need on that probability. This should come from the consequences of a crash should it occur, which typically has just 2 parts: what we would hit, and how hard. The importance of the "what" is obvious. For example, we want to be even more certain to avoid ploughing into a bus queue of people than into a wheat field. “How hard" the impact would be comes from the relative speed of the objects involved. This highlights the difference between hitting something travelling in the same direction as us versus something stationary or even coming towards us. Crucial distinctions!

Remember: Speed, Surprise, Space. Deliberately managing all three is necessary to reduce your level of danger, and to control the situation you are in.


About driveAbility

This risk model is one of eight defined skills of safe driving that have emerged from a very radical re-examination of the driving task in a project called “driveAbility “. Unfortunately, it is even more evident from this work that the most critical skills are not taught when we first learn to drive. Vitally, if the full set of skills is not clearly explained, it seems fruitless to blame drivers for not having them!

You can contact Steve Haley at stevehaley@mail.com

Safe Speed comments:

Steve has provided a remarkable insight into the process of safe driving, not only that but he has produced it with a very memorable key phrase: "Speed, Surprise, Space". Steve also gives us a risk model that demonstrates in three terms why "speed kills" road safety policy cannot work. Brilliant, Steve, thanks for permission to publish. We can't wait to see more of your work. 


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Copyright © SafeSpeed 2004
Created 17/10/2004. Last update 17/10/2004