Monday, March 18, 2013

Safer cars mean worse drivers

If you've read my blog for any length of time you might remember that I subscribe to the theory that safer cars make for worse drivers. My argument all along has been that when you seal people into a quiet cocoon full of entertainment gear, surrounded by safety aids, the drivers begin to assume that the car will save them from their own bad driving. (most recently, see the Driver Education and Toyota Wants To Steer For You posts)
It seems that my theory on this actually has some substance. New research suggests just that - extra safety equipment in cars gives drivers a false sense of security and leads to them taking more risks.
The TRL (Transport Research Laboratory) in England studied crash statistics from 2000 to 2010 and statistical models were developed to look at casualty trends and the effects of car secondary safety improvements. They discovered that, while the number of people seriously injured in road accidents dropped for the first six years of that period, the number of fatalities barely changed. Bear in mind that during the same period there were great improvements in car safety levels with the introduction of more airbags and standard ABS, stability control and traction control on most cars. On higher-end vehicles, things like preemptive braking, radar-assisted cruise control and lane departure warning systems were also becoming commonplace. That all resulted in an increasing number of cars being awarded a five-star crash test safety rating by Euro NCAP.
These advances should have cut fatality rates, but the report's authors warn increasing safety levels may have been counter-productive:
"The reason that the fatality trend was not decreasing up to 2006... may be due to driver confidence – additional safety features in and on vehicles provide additional confidence and some drivers may have adapted their behaviour (ie drive more recklessly) as a result."
The report does go on to say that after 2006, fatalities dropped although the analysis shows that this is most likely because the economic downturn which appears to have had a beneficial effect on driver behaviour, with less speeding and drink driving. The decrease in overall traffic also contributed, especially the large reduction in HGV traffic, and a fall in the number of young male drivers.
The report is available on the TRL website for a small fee.
The TRL are not the first large study institute to come to this conclusion; the American Institute for Highway Safety published similar findings last year - you can read about those in this blog post.
This all begs the question then : why do manufacturers keep loading cars up with this stuff if it's now being proven to be of little or no use? Surely they should be removing this stuff, simplifying and lightening cars and improving fuel economy and safety as a result? Frankly, the more a driver is involved in the act of driving, the safer the roads become because concentration levels have to be higher. That's why drivers who started out on motorbikes are statistically safer car drivers, and that's why cars with manual gearboxes are involved in less accidents - motorcyclists and drivers of manual cars are both more involved in the act of driving (or riding).


Tom McDonnell said...

The phenomenon you describe is known as risk compensation. Wikipedia has an article that gives many examples and sites many studies.

Tyres are another interesting example. I think the effect of fitting tyres having greater levels of grip will increase or decrease safety levels depending on the type of driver, and on the situation.

All drivers will benefit from having grippier tyres if evasive maneuvers are required on a straight section of road, for example if a pedestrian or animal unexpectedly steps in front of a moving car.

When cornering however, whether increased levels of grip confer higher safety levels depends on the attitude of the driver.

Drivers who are skilled and enthusiastic, when driving on uncongested roads, will tend to corner at a speed determined by the road surface and the characteristics of the vehicle they are driving. They will sense the level of grip available through feedback offered by the motion of the car and by the pedals and steering wheel, and choose a cornering speed that offers a comfortable safety margin. These drivers, when given grippier tyres, will increase their cornering speed, since they can do so while maintaining the same comfortable safety margin. The problem with this approach is that while the risk of crashing may stay constant, the severity of the crash will increase sharply - proportionately to the square of the speed. I think many drivers fail to take this into account and so end up less safe with grippier tyres.

Unskilled and unenthusiastic drivers will gain a safety benefit from grippier tyres when cornering, since they lack the skill to determine the level of grip available, and they are not interested in experiencing the thrills of speed. These drivers will tend to drive at the same speed around corners regardless of the road conditions, and regardless of what tyres are fitted. When evasive maneuvers are required, these drivers may be saved by the excess level of grip available that they lacked the skill to detect.

The best combination of driver skill level and attitude (safety-wise) is the driver who is skilled but unenthusiastic. By 'unenthusiastic' here I mean the driver does not seek the thrill of speed, so he does not increase his cornering speed to match the increased grip levels of his new tyres.

The worst combination is of course the unskilled but enthusiastic driver. This type of driver fits new tyres and drives faster due to faith in the new tyres, but does not know how much faster he can drive because he lacks the skill to sense the actual grip level available.

Tom McDonnell said...

An interesting implication of what I've said above, is that for skilled enthusiastic drivers who will always drive according to the level of grip available, decreasing the level of grip by deliberately fitting inferior tyres may actually confer a safety benefit.

What I enjoy about enthusiastic driving is not so much the speed but rather the challenge and feeling of finding the limit of grip available, and cornering, braking, and accelerating at that limit.

I have slick tyres fitted to my mountain bike, which I use for both commuting and cross-country riding. I figure leaving the slicks fitted for my cross-country riding not only saves me the time I would otherwise spend changing tyres, it also allows me to experience the thrills of cornering at the limit of grip at a lower and safer speed than would be possible on knobbies.

Chris said...

This is a good point and it alludes to something I think should be addressed as a whole : unskilled drivers. Nothing improves road safety more than driver training. Drivers who understand their vehicles, vehicle dynamics, road types and surfaces and all the other variables, are undoubtedly safer drivers because they typically don't tend to put themselves in a position where they need the car to save them from themselves.
This is why I'm a huge fan of motorcycling. On a motorbike you can't text, or use the phone, or watch TV. You have to spend 100% of your concentration on the act of driving. You become aware of changes of road surface and how they affect grip. You become aware of sketchy tyres with bald patches and uneven wear. Worn brakes make themselves known. Changes of temperature and climatic conditions are obvious, and all these figure into the act of riding a motorcycle.
When isolated from everything inside a car, separated from the road by electric power steering and brake-by-wire systems, cossetted by climate control systems and heated seats, drivers no longer understand what happens when 2 tons of metal on bald tyres tries to corner on a sketchy road surface. At that point, the car DOES need to save them from themselves.
All the money we spend on safety gadgets could, and should be spent on better driver education. Alternatively, change the driving laws so that, in order to obtain a car licence, you must first ride for 12 months without an incident on a motorbike. I guarantee that if that was the case, road accidents would drop to unseen levels.

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