Speeding by Design

Why do we allow cars to be sold that can do twice the maximum legal limit?

Groups campaigning for further restrictions on the use of cars and motorcycles often pose the question why we allow vehicles to be sold and used on public roads that are capable of speeds more than twice the maximum legal speed limit. On the face of it, this may seem a plausible argument, but in reality it is a complete canard that reveals a profound ignorance of the principles of automotive design.

It is true that the cheapest version of a standard family car such as a Ford Mondeo will reach 127 mph. But these maximum speeds are largely a by-product of improved aerodynamics to allow cars to cruise quietly and economically at the maximum legal speed limit - which, even discounting Germany, Italy and the Isle of Man, is 130 km/h (81 mph) in most major European countries. Cars from 30 years ago with the same weight and power would have maximum speeds 20 mph or more lower.

The only way you can achieve the aim of restricting maximum speeds is via speed limiters. If you tried to “engineer” in a maximum speed little more than the highest speed limit, the vehicle would either have to have the aerodynamics of a house brick (with the consequence of greatly increased fuel consumption and emissions), or be extremely strained and limited in its capabilities at legal speeds. Even a 57 bhp, 1.0 litre Corsa will do 97 mph!

At times, cars like Mondeos need the power to tow 1200 kg caravans, carry five burly blokes and loads of luggage, or climb 1 in 3 hills, but they're not required to do all these things all the time, and therefore inevitably will have surplus power on occasions. Without its speed limiter, the typical HGV tractor unit could top 100 mph when not pulling a trailer, despite actually having the aerodynamics of a housebrick.

As we are part of the EU, any legislation for maximum speeds for cars and motorcycles would have to be brought in on an EU-wide basis. The UK could not go it alone. There is no practical reason why all new vehicles could not be fitted with limiters restricting them to 130 km/h. This might prevent a very small number of high-speed crashes, but on the other hand it would lead to convoys of cars driving “on the limiter” on motorways, which to my mind would increase the total number of accidents. It would also make no difference whatsoever to the overwhelming majority of crashes which occur at speeds well below 130 km/h.

There would also obviously be strong political opposition, particularly from those countries such as Germany and Italy which currently have higher limits. And a key reason why politicians would be very reluctant to do it would be that it would cause a major slump in the motor industry which could plunge the whole of Europe into recession. This would be especially severe if compulsory retro-fitting on older vehicles was not required – but even if it was, buyers would tend to extend replacement cycles and buy less expensive vehicles. It would certainly put virtually all specialist manufacturers from Ferrari to TVR out of business.

The question may also be raised as to why anyone should need a car that is faster or more powerful than the 1.8 litre Mondeo that will reach 128 mph and accelerate from 0 to 60 mph in 10 seconds. In purely utilitarian terms, they probably don’t, but by the same token nobody needs to own a five-bedroom house or a 45” wide-screen television. Such suggestions are advanced in an envious, “tall poppies” spirit rather than out of any genuine concern for safety and do not deserve to be taken seriously in a free society. It is possible to drive irresponsibly in a car of any power level, and the least safe drivers on the road are often young people in low-powered vehicles, while the typical owner of a Porsche or Ferrari is likely to be well over 40 and old enough to know better. In any case, anyone who owns a large, powerful car will pay heavily for the privilege through increased fuel and insurance costs, just as the owners of large houses pay much more council tax.

(July 2004)

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