Peers play an important role in shaping the behaviours of their counterparts at different stages of life. Studies have shown that peer influence/pressure has a significant role in the traffic environment as well as in many other social settings, especially for risky behaviours. Therefore, the aim of this study was to examine age and sex differences in respect of peer pressure and the role of peer pressure on driver behaviour in Türkiye. A total of 405 drivers with a mean age of 23.84 (SD=4.82) years completed an online survey consisting of the Peer Pressure on Risky Driving Scale (PPRDS), the Brief Sensation-Seeking Scale (BSSS) and the Short Driver Behaviour Questionnaire (S-DBQ, measuring aberrant and positive driver behaviour). First, the psychometric structure of the PPRDS, used for the first time in Turkish, was found to support the original structure, addressing direct pressure in the form of risk-encouraging or risk-discouraging and indirect pressure. Indirect pressure was seen to decrease with age for both males and females, whereas risk-discouraging direct pressure increased with age only for males. Sensation-seeking was positively related to aberrant behaviours. Risk-encouraging direct peer pressure and indirect pressure were positively associated with aberrant (risky) driver behaviour, whereas indirect peer pressure was associated with decreased aberrant driving behaviour and increased positive (helpful, polite) driving behaviour. The findings suggested that drivers feel strong peer pressure in traffic, but it varies by age and sex, and this pressure is stronger for young males. These findings have important implications for road safety and intervention studies.