There could be several answers to this question and as there are no options to choose from I will list the ones that make the most sense. Sleep deprivation, illness and chemical influences all affect concentration/attention/reaction time, which can directly result in mistakes while driving. Sleep deprivation, illness and chemical influences all negatively affect your cognitive abilities which need to ideally be alert while driving, this can result in injury or accident when compromised.
The median is usually preferred to other measures of central tendency when your data set is skewed (forms a skewed distribution) or you are dealing with ordinal data.
