A systematic review of the role of peer passengers on young driver behaviour

• Passenger behaviour and driver response may be explained by biopsychosocial factors. • Biological, psychological, and social factors underpin young adult driving behaviour. • Peer passengers may be protective when speaking up to an unsafe driver. • Risk-accepting passengers may increase risky driving behaviours. Research indicates that carrying peer passengers increases the likelihood of being in a crash and is a risk factor for young drivers’ engagement in risky driving behaviours. The aim of this systematic review was to understand biopsychosocial factors that underpin passenger behaviour and/or young drivers’ response from across the world. Database searches were conducted in September 2024, using Pubmed, Web of Science, PsychInfo, TRID, and CINAHL (updated July 2025). A total of 42 studies met the inclusion criteria and were included in the review. Overall, results indicate peer passengers may inhibit or promote young drivers’ engagement in risky driving behaviours, and this can be explained by varied biopsychosocial factors. Passenger behaviour studies typically evidenced that while passengers may be a source of distraction, some may instead aid in assisting the driver to keep their attention on the road. Studies indicated a variety of biopsychosocial factors were associated with passenger behaviour and/or driver response. For example, neurobiological functioning, mood, attitudinal and perception factors, social exclusion, and the relationship between the driver and passenger. The findings highlight the importance peer passengers play in young drivers risky driving behaviour. While passengers may increase risky driving behaviour, they may also encourage safer driving behaviours. Hence, further investigation on the behaviours, responses, and biopsychosocial factors that may promote safe passenger behaviours and driver responses is warranted.