Google will initially build and test 25 pods, mostly in neighbourhoods surrounding its Mountain View headquarters. It will eventually build between 50 and 100, and will broaden testing to sites that are hillier and rainier. The ultimate goal, says Google co-founder Sergey Brin, is computer-controlled cars that can eliminate human error, which is a factor in an estimated 90 per cent of the 1.2 million road deaths that occur worldwide each year. Self-driving cars could also improve traffic congestion and transport the elderly and disabled.