For over ten years, Advanced Drivers of North America [ADoNA] has been teaching the important fact that official “overall stopping distances” for cars have been inaccurate and needed to be treated as being significantly longer than previously thought. Now, at last, our own calculations have been proven appropriate and extremely accurate.
Ever since top research establishments in various countries, such as Monash University in Australia, published findings that adult drivers’ average reaction times are actually in the range of 1.33 to 1.5 seconds rather than the 0.67 sec. which used to be believed, it has frankly been very obvious that stopping distances need to be reassessed and brought out of the dark ages.
The fact is that what are correctly known as “overall stopping distances” consist of two main parts — many argue that it’s three parts but two will certainly suffice for our purposes. These are “reaction time” or thinking time (which translates into distance travelled in that time) and braking distance (which, loosely speaking, relies on a combination of the type and condition of the brakes, the type and condition of the tires, the type and condition of the road surface, and the driver’s ability).
Very recent research by the Transport Research Laboratory [TRL] now proves that stopping distances should indeed be increased because of the above-mentioned fact that drivers’ “thinking time” had been underestimated.
At ADoNA (which until 2016 existed without the word ‘North’ in its full title), I calculated the following stopping distances in 2005 and we have been teaching them ever since then, as follows:
- 20mph – 60ft
- 30mph – 105ft
- 40mph – 160ft
- 50mph – 225ft
- 60mph – 300ft
- 70mph – 385ft
The figures in the following table show that I had an approximate error of just 3 percent throughout, in our chart above, so given that we are talking about average distances, we are more than pleased with that result.
The new, official, average ‘overall stopping distances’
| Speed | 20mph | 30 mph | 40 mph | 50 mph | 60 mph | 70 mph |
| New figures (TRL) | 62ft | 112ft | 167ft | 233ft | 312ft | 397ft |
| Old figures | 40ft | 75ft | 118ft | 174ft | 240ft | 315ft |
| Difference | 22ft | 36ft | 49ft | 59ft | 72ft | 82ft |
Yes, I confess that this all sounds boastful but this situation shows how determined we are at Advanced Drivers of North America to maintain maximum safety information and standards for our clients and trainees. Indeed, this news shows that at ADoNA we were over a decade ahead of the conclusions of this latest research and frankly – with no disrespect intended – we don’t expect many (if any) of our competitors to pick up on this research, even now that it has been published, let alone the correct allowances that need to be made for maximum safety on wet or icy roads! Check out this assertion, as well as other research-based and best-practice based outcomes for yourselves if you are looking for driver safety consultants or training in North America, now or in the future!
Our gratitude and recognition go to the road safety charity Brake for their part in triggering and presumably funding the TRL research on which this article has been based.
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Cuerden, R. (2017). The mechanics of emergency braking. Transport Research Laboratory: http://www.brake.org.uk/assets/docs/pdf/The-mechanics-of-emergency-braking-2017.pdf
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Eddie Wren, CEO & Chief Instructor — Advanced Drivers of North America
