A Longitudinal Survey Exploring the Psychological Determinants of Concealed Smartphone Use While Driving: Insights from an Expanding Theory of Planned Behavior

Concealed smartphone use while driving (CSUWD), a prevalent and covert form of distracted driving, poses significant threats to road safety. However, the psychological determinants underlying this illegal behavior remain underexplored. A two-wave longitudinal study based on the expanding theory of planned behavior (TPB) investigates the intention and prospective behavior of CSUWD in China. In the first wave, 256 respondents assessed the standard TPB constructs, alongside extended constructs of descriptive norms, moral norms, and perceived risks. Subsequently, 156 participants reported their actual behavior in the second wave. Hierarchical multiple regression results revealed that the traditional TPB variables accounted for 57.1% of intention variance and 45.2% of behavior variance, while extended variables contributed an additional 11.7% to intention variance. All variables, except perceived crash risk, emerged as significant determinants of intention. Notably, the perceived risk of being caught and fined inversely correlated with intention, suggesting a potential disinhibition effect. Both perceived behavioral control and intention were significant determinants of subsequent behavior. The findings underscore the validity of TPB in predicting CSUWD, informing the design of non-legal interventions (e.g., public education advertisement, road awareness campaigns, and technological interventions) to mitigate CSUWD-related distracted driving and promote sustainable transportation systems.