According to the passage, how does a 1 per cent rise in average speed affect the risk of a fatal crash?

About 1.16 million people die in road crashes every year, and between 20 and 50 million more are injured, many of them left with a disability. Road crashes are the leading cause of death for children and young people aged 5 to 29. Low- and middle-income countries have about 60 per cent of the world's vehicles, but 92 per cent of the world's road deaths.

More than half of those killed are pedestrians, cyclists and motorcyclists, the road users with the least protection. Men are about three times as likely as women to die in a crash.

Speed is one of the biggest dangers. Every 1 per cent rise in average speed raises the risk of a fatal crash by 4 per cent. For a pedestrian hit by a car, the risk of death rises four and a half times between 50 and 65 kilometres an hour. Drivers who use a mobile phone are about four times more likely to crash.

Simple protection works. Wearing a helmet correctly can cut a motorcyclist's risk of death by more than six times. Wearing a seat-belt can reduce the risk of death for people in a car by up to half, and child seats reduce the deaths of babies by 71 per cent.

The United Nations has set a target of halving the number of road deaths and injuries by 2030.