Conversation and other interactions with passengers while driving induce a level of distraction to
the person driving. This paper firstly conducts a qualitative literature review on the effect of
passenger interaction on road safety and then extends it by using meta-analysis techniques. The
literature review indicated that this distraction due to passengers is a very frequent risk factor,
with detrimental effects to various driving behavior and safety measures (e.g. slower reaction
times to events, increased severity of injuries in crashes), associated with non-negligible
proportions of crashes. Particular issues concern the effect of passenger age (children, teenagers)
on which the literature is inconclusive. Existing studies vary considerably in terms of study
methods and outcome measures. Nevertheless, a meta-analysis could be carried out regarding the
proportion of crashes caused by this distraction factor. The selection of studies for the metaanalysis was based on a rigorous method including specific study selection criteria. The findings
of the random-effects meta-analyses which were carried out showed that driver interaction with
passengers causes a non-negligible proportion of road crashes, namely 3.55% of crashes
regardless of the age of the passengers and 3.85% when child and teen passengers are excluded.
Both meta-estimates were statistically significant, revealing the need for further research,
especially considering the role of passenger age.