Don't wake the tiger

The sleeping tiger represents the countless millions of accidents that don't happen each day


The biggest fallacy in road safety comes from looking at accidents and considering how they might be lessened. Much modern thinking is targeted towards reducing the consequences of "inevitable" accidents. But there's a fatal flaw in this approach. We call it the sleeping tiger.

Meet the tiger

The tiger is made of the countless millions of accidents that don't happen each day. SafeSpeed has long looked at driving as a continuous process of accident avoidance. In many ways it's obviously true. If you close your eyes while driving for just 10 seconds an accident is highly likely. If you make one big mistake (for example: driving through a red light) an accident is highly likely. If you misjudge just one bend an accident is highly likely.

But drivers go for an average of about 7 years between accidents. In the examples quoted, they successfully navigate tens of thousands of bends, many thousands of red lights, and they don't once stop paying attention for ten seconds.

If we do something which reduces the average driver's concentration or attention by just 1% we won't be able to see the difference in any individual but the number of mistakes (and hence the number of accidents) across the entire population could increase considerably. We'd call that waking the tiger. Let's look at the sorts of probability mechanism that describe rare events in a large population.

Tossing coins

Accidents are governed by the rules of probability. Looking at the averages doesn't much illuminate understanding. We need to look at exceptional events.

Imagine giving every one of the UK's 30 million drivers 22 coins. Every day every driver tosses all 22 coins. On average, every day 7 of them will toss all 22 heads. 7 is about the number involved in a fatal accident each day on UK roads. Being involved in a fatal accident on a particular day isn't likely -  it's about 4 million to 1 against - yet every day around 7 are involved. Tossing 22 heads is about the same risk as a fatal accident.

The statisticians and most road safety people would look at "the 11 head average", or they would look very closely look at the individuals who had tossed 22 heads.

Everyone forgets to look at all the people who tossed 21 heads and nearly lost their lives. There's about 143 of them each day. Equally neglected are the 20 heads people who number about 2,861 each day. (We think it's this aspect of probability which causes the ten fold scale on our "ten" page. (click here)). 

So here's another view of the tiger, it's the large number of people who narrowly escape the 22 head fate every day.

What would happen if we collected one coin for each of the drivers (leaving 21 coins each) and ruled that 21 heads was the fatal total? Fatal tosses would immediately jump from 7 each day to 14 each day.

In the real world drivers have different skills, experience and  attention levels. That's equivalent to having differing numbers of coins or perhaps different "all heads" thresholds. But the sort of probability that governs the coin tossing is exactly the sort of probability that governs fatal accident (and indeed all accidents).

If we've going to change something, we must consider the near miss groups as well as the hit groups. Minute changes could easily tip an extremely unlikely miss into an extremely unlikely hit. And that's when we realise that we've awoken the tiger.

Changes in drivers

We know that drivers are affected by speed cameras. We know that drivers are affected by the law, and we know that drivers are (perhaps to a lesser extent) affected by publicity messages. Here are a few example real changes:

  • Some drivers keep a lookout for speed cameras
  • Some drivers stick to the speed limit more than they used to
  • Some drivers have purchased speed camera location devices
  • Some drivers have been prosecuted for speeding by speed camera pictures
  • Some drivers have neglected registration requirements because of speed cameras
  • Some drivers are angry about speed cameras
  • Some drivers worry about speed cameras
  • Some drivers check their speedo more than they used to
  • Some drivers now think that they will be safe if they stick to the speed limit
The important point of this list is that drivers are affected by speed cameras. It's not just slowing them down, it's altering the way they think and things that they prioritize when they're driving. It's these alterations in driver's priorities that risk waking the tiger.

Some of those that would not have had an accident now might because of the momentary distraction of consideration of a speed camera. It's not just where there are speed cameras. It's everywhere there might be a speed camera.

But it isn't just that. We've been telling drivers for a decade now that they must stick to the speed limit to be safe. There are many - probably millions - of drivers on UK roads who watch the speedo and regard it as a barometer of safety. Of course it's no such thing, but for every second that they are thinking about keeping to the speed limit to be safe they are NOT thinking about real driver based safety issues. There are apparently even road safety professionals who think like this - see what happened in Stockport! (click here).

There may well be a range of other subtle changes in drivers' thoughts and priorities as a result of concentrating British road safety policy on speed. The fact is that excessive speed over the speed limit is responsible for a tiny percentage of accidents, (see throughout this web site) but we're demanding that drivers keep it high on their list of priorities.

Here's our guess at the top five priorities for the average driver, before and after the speed cameras were introduced.

Rank 1985 2003
1st Observation Observation
2nd Safe space ahead? Safe space ahead?
3rd Anticipation Speed limit and speedo
4th Speed low enough to stop in the safe space? Anticipation
5th Other road users movements Speed low enough to stop in the safe space ahead?

Consider the table a quick sketch. Real drivers priorities are constantly changing and adapting to circumstances. But enforcement practice has inserted a non important concern high on the driver's priority list. If you think the speed limit and the speedo should be an important concern, consider how successful your own driving might be with a dead speedo. Would it really make a difference?

Safe speed warns that these false priorities are waking the tiger.

"If only drivers would just stick to the speed limit..."

We frequently hear people say: "If only drivers would stick to the speed limit they would be safer and need have no fear of enforcement." We hope this page will demonstrate the basic fallacy of the assertion.

As we saw above, if drivers prioritize the speed limit above some other driving task, then "some other driving task" is inevitably pushed to a lower priority position. This is a far larger and more important effect than the tiny benefits of keeping to the speed limit. Accidents happen when drivers make mistakes. Sometimes that mistake might be driving too fast for the circumstances, but it's never simply exceeding the speed limit. We'll get the lowest casualty rates when our drivers are working to the best priority list.

There are exceptions. Some people (only a few percent) are just maniacs. They drive faster than is safe, sometimes above and sometimes below the speed limit. In such cases the Police and the speed limit laws are a great solution.

For the rest of us, we need to be helped to use skill and speed with a high degree of responsibility and a proper set of priorities. Anything else will wake the tiger.

"If everyone drove properly there wouldn't be any accidents..."

We also hear people say: "If everyone drove properly there wouldn't be any accidents." This is another fallacy. Actually it is absurd to suggest that anything we could do would make such a radical change. Changes (in either direction) are going to be small increments. Nibble by nibble the accident rate can be changed up or down. At the moment, UK road safety policy appears to be changing our accident rates for the worse. A perfect policy might be able to reduce the fatal accident rate by 7% or 8% per year. But a bad policy will wake the tiger.


We hope we've shown that it's insufficient to worry about the accidents that happen on our roads. It's also vital to consider how the accidents which don't happen are avoided. The only thing preventing accidents from doubling overnight (or even jumping by a factor of a thousand) is the constant effort from our drivers to avoid accidents. To do that job, we must help all our drivers to set the very best priorities.

But the "speed kills" message backed by automated speed enforcement distorts drivers priorities and is waking the tiger. Presently the beast has one eye open and it's looking at us. We've lost the 40 year trend in the fatal accident rate (click here) and the underlying changes are accelerating in the wrong direction.

The researchers and most of the so-called road safety professionals are not paying attention. Meanwhile SafeSpeed can clearly see the tiger beginning to stir...


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speed cameras cost lives

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Copyright © SafeSpeed 2003, 2004
Created Feb 2003. Last update 7/03/2004