Is greater engagement with a gamified app associated with greater improvements in safe driving behaviour? A naturalistic study from the i-DREAMS project

Smartphone-based feedback applications are increasingly used to promote safer driving, yet their effectiveness depends on sustained user engagement. This study examined the role of engagement with the i-DREAMS smartphone application in shaping safe driving behaviour during naturalistic field trials conducted over 18 weeks per participant in Belgium and the United Kingdom (UK) (N = 100). The application provided drivers with post-trip feedback on their driving performance, including safety scores and behavioural insights, and later incorporated gamification elements such as goals, badges, leaderboards, and push notifications to stimulate engagement. Analyses combined descriptive statistics of app engagement, cluster analysis to distinguish low- and high-engagement users, and generalised linear mixed-effects models to assess the effects of engagement, intervention stage, and socio-demographic factors on risky driving events per 100 km. Results showed that drivers primarily engaged with functionalities that provide direct performance feedback, particularly trip summaries and scores, and that engagement increased following the introduction of gamification features. Higher engagement was associated with greater reductions in risky driving events compared with lower engagement, particularly for road-sharing behaviours and total events. The strongest behavioural improvements were observed when in-vehicle warnings, post-trip feedback, and gamification elements were combined. Some cross-country differences emerged, with more consistent intervention effects in the UK than in Belgium. Age and education were also associated with driving outcomes, with older and more highly educated drivers showing fewer risky events in some models.