Like their owners, cars have been piling on the pounds in recent decades. When the Volkswagen Golf was launched in 1974 it weighed 0.75 tonnes and was 3.8 metres long. By 2008, when the mark six Golf was launched, its weight had soared by more than 50% and it had stretched by 38cm. Apart from making their cars roomier, motor manufacturers have added all sorts of gadgets and safety devices and each of these has meant a gain in weight. Finally, however, the pressure from regulators to make cars more fuel efficient, and the rising cost of materials are combining to make carmakers slim down their models.