Background: Previous researchers examined the effects of either drivers' personal characteristics or traffic sign design features on the usability of traffic signs. Their research indicated a connection existed between personal characteristics and usability and between design features and usability.
Objectives: The focus of this study was to investigate which personal characteristics of drivers and which features of traffic sign design affect traffic sign usability the most.
Methods: The study was conducted in three stages. In the first stage, the participants filled out a questionnaire designed to record each driver's personal characteristics. In the second stage, a System Usability Scale (SUS) was used to evaluate the subjective usability of traffic signs. The SUS had 10 statements that participants (N = 386) scored on a 5-point Likert-type scale from strongly agree to strongly disagree. In the third stage, these participants assigned from 0 to 100 points to 20 signs based on participant perception of the five design features of familiarity, concreteness, simplicity, meaningfulness, and semantic distance.
Results: The results showed that four of the five personal characteristics studied (age, education level, possession of a driving license, and formal driving experience) correlated significantly with traffic sign usability. The exception was gender, which did not correlate significantly. Additionally, it was found that the five traffic sign design features correlated in varying degrees of significance with each other and with specific traffic signs.
Conclusions: Traffic sign usability depends mostly both on driver education level and age group and on the design feature of meaningfulness. These findings have implications for how drivers should be trained and how signs should be designed.
Keywords: Driver age; driver education level; driver experience; traffic sign features; usability.