Soap Box Derby racers
These gravity-powered home-built karts are part of a racing programme that started in the US in 1934. With no engine, they rely entirely on gravity to race down a steep road. Traditionally, they are made by children and young adults. The karts might look quite simple, but they can reach speeds exceeding 48 kilometres per hour, and people from around the world compete at the annual Soap Box Derby World Championship finals at the Derby Downs Track in Akron, Ohio. The racers start at a ramp at the top of a hill and before quickly accelerating downhill. The race is over in less than 30 seconds, and a timing-triggered overhead photography system is used to determine the winner of each heat.