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Traffic signs, which are extremely important for traffic safety, aims to regulate traffic by providing information about the characteristics of road and road environment for drivers. The success of traffic signs mainly rely on the easy comprehensibility of its meaning in a short time. Further more, today&rsquo / s global economies and transportation systems emphasize the need for more universial traffic signs which was the main motivation of two main treaties on traffic signs / Vienna Convetion in 1968 and European Aggreement Treaty in 1971, which are signed and followed by Turkey. For an effort to increase traffic safety, a Subcommittee of the Turkish Highway Traffic Safety (THTS) Council requested the determination of comprehensibility of critical signs with higher probability of impact on traffic safety selected by a group of experts from engineers and law enforcement agencies in a survey study. The survey questionnaire included 30 selected traffic signs (including two prohibition signs omitting oblique bar recently changed as a part of the European Union Participation Process) and 9 control group signs, a total of 39 traffic signs, and driver characteristic questions, such as gender, age, educational background, etc. to reveal insights about a) the level of comprehensibility of different groups of traffic signs and and b) driver characteristics that may affect the comprehensibility of these signs. A pilot study in the city of Ankara is conducted over a sample of 1,478 surveys. Answers for the meaning of each sign are coded using a scale of five (opposite, wrong, no comment, partially correct and correct responses). The results showed that the control group signs have very high comprehensibility as expected, while some of the critical signs were not known much, or mistaken for others, even mistaken for opposite meanings. The certain loss of comprehensibility of the traffic signs changed recently is seen in the comparative analysis of the signs before and after the change, as well as significant shift towards an opposite meaning. The significance of driver characteristics (gender, education, occupation etc.) affecting the comprehensibility of the traffic signs varies among traffic signs and characteristics. As the result of this study, (THTS) Council decided to support traffic and driver education more and mass promotion of mis- or un-comprehended signs without searching for more local solutions or versions.