Age undoubtedly affects the learning process. The older somebody is when he or she starts to drive after full licensing, the lower the accident risk will be at the start of his or her driving career.
Studies have demonstrated that, beyond the age of 18 the human brain is still developing, in particular the areas dealing with 'executive' functions like planning, impulse control, reasoning and the integration of information (i.e. thinking before acting). This could have an important influence on how to prevent young driver crashes, particularly as the combined abilities to take responsibility, to reflect on consequences, and to control impulses play an important role in driving safely.
The late maturing of parts of the brain is not the only biological aspect relevant to young drivers' road safety risk. There is also a positive correlation between sensation-seeking and testosterone levels, which provides a very basic explanation for why men are more likely to show risky behaviour than women. Biological development is nevertheless significantly influenced by experience. Social and contextual factors may explain behaviour patterns. As there is such a close relation between nature and learned aspects, educational programs should always be aware of the limitations posed by the biological aspects.
An other factor which can be related to immaturity is that young, novice drivers are in the middle of a socialisation process in which they are getting away from their parents' influence to become independent. The problem appears when during that process they are strongly influenced by peers, who may not be a good role model for safe driving.