Comprehensibility of traffic signs in Turkey: The effects of cognitive sign design features and user factors

Traffic signs are the main tools to regulate, warn and guide the drivers. The correct and easy comprehension of traffic signs is essential for the effective traffic control and safe driving. The traffic signs that are currently used in Turkey are based on the Highway Light and Road Signs agreement that have signed in Vienna on 8 November 1968 and the European Agreement Supplementing have signed in 1971 to define international uniformity in rules managing the road signs, markings, signals and symbols. It is known that comprehension varies widely among different traffic signs symbols, road user characteristics. Therefore, the main objective of this study was to examine the comprehensibility of Turkish traffic signs, investigate the effect of cognitive sign design features and user factors on comprehension, and understand the interrelationship between them. 100 male and 101 female volunteers aged between 18 and 69 years with family roots from all seven regions of Turkey were the participates of the study. 60 Turkish traffic signs were guessed and five cognitive sign design features; familiarity, concreteness, simplicity, meaningfulness and semantic closeness were rated by participants for the each sign. The effects of age, gender, marital status, educational background, active car driving experience and smoking habits were evaluated in the study. Through statistical analyses descriptive values of comprehensibility score, guessability score and the effects of cognitive sign design features and user factors on guessability score were determined. Current traffic signs were not guessed well with the 39.2% guessability score by the population. More than 50% of the participants could not guess the meaning of the 35% traffic signs. 5 signs were comprehended as opposite of their true meaning. In terms of cognitive sign design features, Guessability score was highly and positively affected by familiarity, meaningfulness and semantic closeness. Traffic signs with high scores of familiarity, meaningfulness and semantic closeness were guessed well and found more comprehensible by the population. Age, marital status and active car driving experience were found as significant predictors of Guessability score. Guessability performance decreased with age and increased with the increase of active car driving experience. Guessability performance was not related with the educational background and gender. Road works sign was found more familiar, concrete, simple, meaningful and semantically close, followed by warning type signs by the population. Age, active car driving experience and sign type were found as significant predictors for all five cognitive sign design features. This study evaluates the effect of both the sign design features and user factors on the sign comprehension.The results can serve as a reference in design of traffic signs not only in Turkey but also in the world.