Yet Another Problem

Lower speeds might mean less time to react

Preliminary - for discussion


About a week ago,  a highly trained Police driver remarked to me: "Of course you don't really start to learn to drive until you're driving well in excess of the speed limits". I admit the remark struck a chord with my own experience from many many years ago. But does it have any relevance to road safety in general or "ordinary" drivers? I thought not, but now I'm worried. It might actually turn out to be very important indeed. Here are my thoughts on the subject for discussion...

Becoming experienced

We know very well that experienced drivers have far lower average crash risks than novices. The most general reason for this is that the experienced driver knows what to expect (from the road, from other drivers, from the weather and from their own vehicle), and the most important component of becoming experienced is probably improved hazard perception.

As hazard perception improves, so we tend to look further ahead. This genuinely provides more time to react. Looking "far enough" ahead is probably the single most important driver skill. Whatever happens, if we are successful at looking and thinking far enough ahead we simply don't crash.

Growth of experience follows this sort of pattern:

I expect everyone will agree that experience grows more quickly at first and more slowly later. I expect everyone will agree that after about 8 years it's fair to call yourself an experienced driver, and I expect everyone will agree that you never stop gaining in experience. I certainly hope I never stop learning.

But what if there was a factor that altered the slope of the curve? What if it starts to take the average driver 10 years to become experienced at the "90" level shown? And what if some drivers stop gaining experience after they have reach some sort of personal comfort zone? - For some individuals this might be below half of the average.

The influence of the average

We are confident that our national accident rate is set by the quality of the average driver. Any small change in the quality of the average driver will be directly reflected in the accident rate. We do not believe that the quality of the average driver has changed very much over time except in the last decade when the average driver quality has fallen markedly and tended to swamp the engineering benefit.

Raising the vision

One of the constant themes of driving instruction is to "raise the vision" and look further ahead. This clearly goes to the benefit of earlier hazard perception and provides more time to react if something is going wrong ahead.

The majority of real world accidents are the result of drivers not looking or thinking far enough ahead.

It follows that if the average look-ahead changes, then the number and severity of accidents is also likely to change.

"Time to react" attitude proxies

Safe Speed believes that a critically important factor in UK road safety has been the leakage of advice and skills from the Police driver training school at Hendon (the only centre of driving excellence in the World). One of the things that Hendon gave us is pull-push steering. Pull-push steering has several advantages, but Safe Speed believes that the greatest advantage of pull-push steering is that it's slow. This slowness has caused generations of drivers to look a few precious tenths of a second further ahead. Other Hendon recommended techniques fit the same pattern - they take extra time and that in turn causes the vision to be raised and drivers to look and think further ahead.

The problem itself

Here's the proposition:

By asking drivers to drive more slowly with highly enforced speed limits, we risk creating a generation of drivers who:

  • look less far ahead
  • gain experience more slowly
  • reach a lower peak level of experience

We believe that the adoption of Hendon recommended "attitude proxy" techniques have been very important in achieving the safest roads in the World. It follows that those few tenths of a second of reserve in the average UK drivers' margin are critically important in delivering our superior road safety.

If we are right about those precious tenths of a second, then it follows that any recommendation to drivers that asks less of them may lead directly to poorer average performance.

If the majority of accidents took place at speed limit speeds, and we enforced speed limits more rigidly then we might be delivering time to react out of the reduced average vehicle speeds. But the average accident takes place well within the speed limit after drivers have adjusted their speed. Assuming that the adjusted speed is normally no different whatever the speed limit or enforcement, it follows inevitably that drivers' time to react margins are delivered out of their attitude and their hazard perception rather than any limited speed.

We therefore tend to believe the proposition that highly enforced speed limits will lead to slower learning and ultimately to the average driver looking less far ahead. This in turn would lead to an increased accident rate.


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Created 7/04/2004. Last update 7/04/2004