**5. Conclusions**

The main aim of this field study was to test whether differences between detection and readability accuracy of market-ready TSRS exist and to what extent, as well as how different "graphical changes" affect their accuracy. A total of 17 cars from 14 brands were tested. Fourteen cars were from different manufacturers while three were from the same manufacturer. The results confirm that TSRS accuracy differs between car brands and even between the same brand, although, due to a limited sample, this needs to be further tested. Furthermore, graphical changes significantly affected the accuracy of the TSRS in all vehicles compared to the control condition (ranging from 62% to 99%).

Based on the results and limitations of this study, future research should investigate TSRS accuracy on real roads with other traffic present and in different conditions as well as different types and quality of traffic signs. In order to develop a deeper insight, the technical data about the installed TSRS should be analyzed in order to evaluate each system and its limitations. Furthermore, a detailed elaboration of standardization methodology and principles should also be developed.

**Author Contributions:** Conceptualization, D.B. (Darko Babi´c) and D.B. (Dario Babi´c); Methodology, D.B. (Darko Babi´c), D.B. (Dario Babi´c), M.F. and Ž.Š.; Formal analysis, M.F., D.B. (Dario Babi´c) and Ž.Š.; Investigation, D.B. (Dario Babi´c) and M.F.; Resources, D.B. (Dario Babi´c), M.F. and Ž.Š.; Writing— D.B. (Darko Babi´c) and D.B. (Dario Babi´c); Supervision, D.B. (Darko Babi´c); Project administration, D.B. (Darko Babi´c); Funding acquisition, D.B. (Darko Babi´c). All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was a part of the project entitled "Establishing a Methodology for Testing and Evaluating the ADAS Systems" funded by the University of Zagreb (Potpore za temeljno financiranje znanstvene i umjetniˇcke djelatnosti Sveuˇcilišta u Zagrebu u ak. god. 2019./2020.).

**Data Availability Statement:** The data used to support the findings of this study are available from the corresponding author upon request.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Appendix A Results for Each Vehicle per Each Scenario**


