The number one killer of young people (defined as 15-29 year olds) in the world is road related deaths.
In the UK there were 1730 traffic deaths in 2015. There is often more than one contributing factor, however it is claimed 90% to 95% of the time driver error was one of the contributing factors. While the data available does not give us a precise number of how many definitely included driver error, we can see an overwhelming majority of the time that a contributing factor is driver error.
Driver failed to look properly and driver/rider failed to judge other person's path of speed are the highest contributors by a considerable margin and issues relating to speed are secondary, while other issues trail behind considerably.