Effects of an adult passenger on young adult drivers’ driving speed: Roles of an adult passenger's presence and driving tips from the passenger

•We demonstrated a passenger effect on young drivers in an experimental setting.•Driving tips from an adult passenger rather than the passenger's mere presence facilitated safe driving for young drivers.•The positive effect of passenger's advice retained even when young drivers were transferred to a solo driving situation.

An adult passenger has been known to facilitate young drivers’ safe driving. This study examined whether the adult passenger's effect is produced by the simple presence of an adult passenger or by the driving tips offered by the passenger. Further, we examined whether the effect would be transferred to when a young driver drives alone without the adult passenger in the following session. Three groups of participants drove on expressway in a driving simulator, either alone, with a silent adult passenger, or with an adult passenger who gave advice on driving safety. After a break, participants in all three conditions drove on the same expressway alone. Results showed that participants who drove with an adult passenger providing driving tips drove more safely than the other groups, and the effect was transferred to even when they drove alone afterwards.