# Temporary Road Marking Paint for Vehicle Perception Tests
## 5 Discussion
With constant performance improvements of lane detection systems, it is plausible to assume that the importance of reproducible, worn road markings will rise. Due to the different weather influences between the first trial phase in 2022 and the second trial phase in 2023, this study is limited in a sense in that the results from these two phases cannot be compared to each other. Furthermore, we utilized a smartphone camera and a parallel orientation toward the road marking to measure the contrast. Angles of forward-facing vehicle cameras might result in different contrasts perceived by the driving system. In addition, the retroreflectivity measured immediately after the application might be higher when a different type of retroreflective bead is used. For the tested road markings with retroreflective beads, visibility is most likely not only attributed to the paint but also to the beads. The adhesive properties of different types of beads might also influence the changes in visibility of the road marking over time. Suggestions regarding the maintenance of the road marking paints after rain events could be improved by investigating the correlations between the durability of the road marking paint and precipitation parameters in a different experimental setup. Individual, intense precipitation events could have a greater impact on the durability than longer-lasting rainfalls with lower precipitation intensities or vice versa. The threshold values for retroreflectivity from German standards were selected since the proving ground where the experiment was conducted is in Germany. In addition, the German threshold values for the reflected luminance of used road markings of 100 mcd/(lx \(\times\) m\({}^{2}\)) at night (retroreflectivity) and 130 mcd/(lx \(\times\) m\({}^{2}\)) during the day (diffuse reflectivity) [7] are among the highest requirements in an international context. For instance, the minimum value for China is 80 mcd/(lx \(\times\) m\({}^{2}\)) retroreflectivity [9]. In the United States of America, the minimum retroreflectivity is 50 mcd/(lx \(\times\) m\({}^{2}\)) for driving speeds between 35 and 70 mph and 100 mcd/(lx \(\times\) m\({}^{2}\)) for driving speeds greater than 70 mph [8]. However, there are examples of higher minimum threshold values, such as in the United Kingdom where 150 mcd/(lx \(\times\) m\({}^{2}\)) is required for used road markings in unit areas [10]. This study's aim was to examine whether the usage of water-based paint for road markings with complex geometric shapes for vehicle tests on proving grounds is generally a promising approach. For economic reasons, only four paint samples were manufactured and tested. Based on the results, a more thorough investigation is recommended that investigates correlations between different percentages of binder, coalescing agent, and pigment (independent variables) and changes in visibility as well as residue after removal (dependent variables) while controlling for effects from vehicle overruns and different weather parameters (precipitation, temperature, humidity, etc.). Appendix B provides a research model for a follow-up study. The considered independent and control variables are expected to significantly correlate with changes in visibility over time and removability without creating phantom tracks. One desired attribute of temporary road marking paint for test maneuvers on proving grounds is that the visibility does not change over the course of a test drive. We have defined durability as the paint's capability to resist removal by precipitation and vehicle overruns. Yet, another target attribute of the paint is that it is easily removable on demand without leaving phantom tracks (i.e., residuals of paint or the altered macro texture of the asphalt).