The Dula Dangerous Driving Index: an investigation of reliability and validity across cultures.

The aim of this study is to further establish the validity and reliability of the Dula Dangerous Driving Index (DDDI). The reliability and validity of the instrument was investigated by comparing data from a US university sample, a US community sample, and a sample of Belgian traffic offenders. Exploratory and confirmatory factor analysis supported the presence of a four-factor structure with items for Drunk Driving forming a separate scale apart from items for Risky Driving, Negative Cognitive/Emotional Driving and Aggressive Driving. A multi-group confirmatory factor analysis with model constraints supported the validity of the DDDI. Inter-correlations revealed that the DDDI subscales are closely interrelated and uni-dimensionality of the measure was found in all three samples. This suggests the DDDI Total score can be used as a composite measure for dangerous driving. However, the validity of the subscales was demonstrated in the Belgian sample, as specific traffic offender groups (convicted for drunk driving, aggressive driving, speeding) scored higher on corresponding scales (Drunk Driving, Aggressive Driving, and Risky Driving, respectively), indicating that it is clinically meaningful to differentiate the subscales.