Time to react is the most fundamental part of our road safety system. Whenever road user have time to react to dangers or changing circumstances they can avoid a crash.

What is time to react comprised of? How can we give more time to react to road users? 

Time to react is delivered out of the following major components:

driver attention and concentration

It stands to reason that if you're not paying attention to the road ahead when something starts to go wrong, you'll have less time to react when you are again paying attention.

It stands to reason that if you don't have a clear view ahead, and into the spaces where something could enter your safe braking zone, that you will not be able to react if another road user encroaches into your safe space ahead.

Looking is one thing. Understanding what you see, and looking at the right thing at the right time is something else. As drivers develop experience, they get better and better at looking in the right place at the right time.

Anticipation in this context is the term used to describe how drivers use imagination to extend their observation into a worse case risk estimate. Often something that we see forewarns of something that might be about to happen. The classic example is a ball bouncing into the road. Our skilled driver automatically anticipates the child chasing the ball.

Observing and anticipating are not of much use unless we act on what we've seen. Once a hazard has been observed we must plan how the hazard is to be dealt with. This is the essence of a driving plan - we know exactly how we are going to negotiate a hazard before we get there.

Everyone makes mistakes. How do you build in a tolerance for error in your driving plan? Safe Speed recommends never planning to use more than half the available braking effort. That way you will always have the possibility of braking harder if things don't work out exactly as expected.

It always takes a finite amount of time for a hazard to encroach on your planned path. If you expect to pass within inches of another road user, then they can encroach on your planned path very quickly. On the other hand, a large lateral separation means much more time to react. 

Did you happen to be looking in the right direction when something happened, or were you checking your mirror? Did you happen to spot a glint through a hedge that warned of a fast approaching vehicle or did you miss the one tiny clue? In a potential accident situation, luck will play a significant part. The tricks here are to have a margin for error and to miss the smallest possible number of clues. 

If you have chosen the right speed to negotiate a hazard safely, speed does not contribute to time to react. This follows from forward planning. If the speed is too high to allow time to react then some other part of the safety system has failed. If such a failure has taken place, then travelling faster - it would have to be too fast for the conditions - would reduce the available time to react.

The proponents of speed camera road safety imagine that you're driving merrily along and then all of a sudden something happens and you crash. They argue that the faster you are travelling at the time of the crash the more damage will be done. Their imagination tells them that you won't have time to brake and that whatever speed you were travelling at will be the impact speed.

Such views are very far removed from reality, in particular:

• They don't fit with the log scale of accident severity (click here)
• They don't fit with the pedestrian casualty severity ratios (click here)
• They don't fit with the ratio of car driver fatalities (click here)
• They don't allow for negative side effects on drivers' attention, concentration and observation (click here)
• They don't allow for any negative side effects on drivers' skills developments (click here)
• They don't account for the common accident contributory factors (inattention, carelessness and misjudgement)
• They assume that "accidents will happen" and thereby miss the chance to implement policies that will improve drivers' chances of avoiding accidents.
• They fail to recognise the huge value of the "closed loop" hazard speed feedback system that drivers use accurately and instinctively.

The main objective of good driving is to deliver "time to react" whenever it might be needed. This means looking and thinking well ahead and always being ready for anything that happens. 

Time to react is unlikely to ever be delivered by choosing to drive at the speed limit - time to react is only delivered when the speed chosen takes all the immediate conditions into account.

Time to react is closely related to the safe speed for the circumstances - if you can always stop comfortably, on your own side of the road within the distance that you know to be clear - then you also know that you have time to react.

How do we recognise a road safety system failure? Is it only when there's an accident? No. The following are all safety system failures whether or not an accident takes place:

• emergency braking
• swerving
• being surprised by another road user
• losing control

Time to react is delivered out of sound driving practice. The fact that we are able to go 7 years between accidents on average indicates that drivers are extremely capable at avoiding accidents most of the time. A good policy would build upon this obvious strength, but modern bad policy ignores the strength and concentrates on attempting to minimise the damage in the comparatively rare crashes.

Unfortunately the negative side effects of modern (speed kills) road safety policy outweigh the potential benefits by several orders of magnitude.

Instead we need to implement policies that help drivers to concentrate, observe, anticipate, plan and allow excellent margins for error. We know that there's massive room for improvement because our average driver is a long way from the ideal.

Safe Speed demands an urgent return to real road safety.

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