5,000 years ago an unknown genius invented the wheel, or more accurately speaking the wheel and axle which allowed the wheel to be fixed to a structure such as a cart. It is indubitably the most important invention in the history of man, the start of technology, opening up limitless opportunities. Of course it has also created more than a few problems. One that has taxed the limits of human ingenuity since the first wheels started turning – is how to stop them; and whatever they are attached to it, be it cart, carriage, car or train. Of course once the driving force is removed, friction will cause the wheel to slow and eventually stop turning. But one of the reasons wheels are so useful is that friction acts less on a wheel than say on a sled runner, so this natural method of stopping is generally too slow in most instances. Brakes were devised to overcome this problem and, with many significant advances in design and some innovative technology, have proved invaluable in slowing and stopping wheeled vehicles.
Brakes do however suffer from one major drawback; someone needs to operate them. Bearing in mind that people generally drive a car with the aim of going rather than stopping, a great deal of effort has been put into persuading drivers to apply their brakes. These include traffic lights, stop signs, traffic cameras and police. The problem with these methods is that they require a complex support system involving infrastructure, law, politics, psychology and education. A very basic but extremely effective approach is the use of a physical barrier. Faced with a row of stainless steel bollards most drivers will quickly bring their car to a halt or at least divert it along an alternative route. The type of barrier needed depends upon the circumstances including the probable speed of a vehicle, the state of mind and personal inclination of the driver and the potential risk. When a vehicle is being parked for example, moving at a very slow speed, and with a driver who is disposed to stop, a concrete wheel stops only 90 – 100 mm high is usually sufficient.
Of course sometimes the aim is not just to stop the vehicle but to keep it stopped for a period of time which requires a somewhat different approach. Wheel clamps can be used to physically hold a car hostage pending payment of a heavy ransom. Locked doors and car immobilisers can prevent someone starting a car without the key. The wheel of a bike can be locked to a bicycle parking racks to keep it stationary, know more. Although a thief may of course leave that wheel and remove the rest of the bike unless the frame is also secured. And the efforts continue. Technological advances have opened up a range of new possibilities, including cars that warn the driver of an imminent impact and ones that apply the brakes automatically. The invention of the wheel started us on a long journey; how far will our attempts to stop the wheel take us?