The drivers are a central component of traffic system, and their limitations, constraints, needs, motivation, level of alertness, and personality define their behaviours on the road. Understanding the determinants of the driver's behaviour is crucial to find solutions for the serious problem of road accidents.

This study aims to investigate the reliability and the construct validity of the Portuguese version of the driver behaviour questionnaire (DBQ; Reason et al., 1990; Portuguese version: Correia, 2014), using exploratory and confirmatory factor analysis (EFA and CFA) in a sample of Portuguese population.

Participants answered an online survey including socio-demographic questions and the DBQ. Inclusion criteria were: driving license and regular driving for at least three years and age lower than 75-years-old. The sample is composed of 747 participants [417 (55.8%) women; mean age=42.13±12.349years; mean driving license years=21.30±11.338; mean years of regular driving=20.33±11.328]. The total sample was randomly divided in two sub-samples. Sample A (n=373) was used to EFA and sample B (n=374) was used to CFA.

The most acceptable model was the three-factor model found with EFA, excluding items 1 and 24 (χ²/df=2.01; TLI=.86; CFI=.88; RMSEA=.05, P=.315). The internal consistency analysis resulted in: infractions and aggressive driving, α=.77; non-intentional errors, α=.73; lapses, α=.71; total DBQ score, α=.84.

These results suggest that the Portuguese version of the DBQ is a valid and reliable measure to assess self-reported driver behaviour in the Portuguese population.