# An Augmented Warning System for Pedestrians: User Interface Design and Algorithm Development
## 4 Discussion
Considering the overall size of the screen was 2.31 by 1.16, the error of 0.253 was acceptable. In general, the error from slope was smaller, which meant the direction of the vehicle path was correct, and the distance between the two paths was larger, which meant the vehicle path may not have been overlaid on the exact lane in which the vehicle was coming. The errors may have been due to an error from the GPS signal. Better GPS hardware may be able to reduce such errors. Overall, the projection algorithms projected the information in the warning window correctly. In summary, the developed warning system can clearly show the necessary information. As a system designed based on AR glasses, no extra carry effort is needed from pedestrians. The pedestrian still can see the real world while the warning system is on. Compared with a phone screen-based system [8], it could cause less distraction for pedestrians to receive real world information. Additionally, since it is a graphic warning system, pedestrians can receive more visual information compared with audio or vibration warning systems [9]. Such a system has the potential to deliver an effective warning to pedestrians who have lower situational awareness or are distracted and protect them from potential conflict. It can also give pedestrians information about an incoming vehicle when the oncoming vehicle is blocked by other objects or buildings on the street. Moreover, this warning system can be applied in other situations. Since the input of this warning system only requires GPS and IMU of the vehicle and the pedestrian as well as the expected conflict location, it can integrate with any system that has such outputs. This design could be further extended into the autonomous driving environment, where it can give a warning to the pedestrian when there is some malfunction happening in an autonomous vehicle and the autonomous vehicles have potential to collide with the pedestrian. A few limitations in this study should be acknowledged. First, the interface was not designed for situations in which multiple conflicts are detected. Future work could focus on the scalability of the designed system to include multiple conflicts simultaneously. Additionally, since current AR glasses are still too bulky and heavy to wear daily, the whole system is not supported by the existing hardware. In addition, current commercial AR glasses have a limitation on their field of view as well. The field of view of AR glasses is small; for example, the Microsoft HoloLens has only about a 35\({}^{\circ}\) by 17\({}^{\circ}\) field of view, and the Sony glasses are even smaller at 19\({}^{\circ}\) by 6\({}^{\circ}\)[33]. Thus, the designed size of the warning window, which is 60\({}^{\circ}\) by 30\({}^{\circ}\), cannot be fully shown in current AR glasses. Lastly, no quantitative evaluation was done for the user interface design. The reliability of the subjective evaluation is a concern, and objective measures could provide further information regarding the performance of the design. Objective evaluations, such as the subject's response time, accuracy, correct body physical response, etc., could be done further to quantify the effectiveness and the accuracy of the warning system. Conceptualization, Y.T. and B.J. ; methodology, Y.T. and B.J. ; software, Y.T. ; validation, Y.T. ; formal analysis, Y.T. ; investigation, Y.T. ; resources, B.J. ; data curation, Y.T. ; writing--original draft preparation, Y.T. ; writing--review and editing, B.J. and S.B. ; visualization, Y.T. ; supervision, B.J. ; project administration, B.J. ; funding acquisition, B.J. All authors have read and agreed to the published version of the manuscript. Research was funded by Michigan Mobility Transformation Center under grant number AWD001508. Not applicable. The data presented in this study are available on request from the corresponding author. The data are not publicly at this time due to sponsor agreement and as the data also forms part of an ongoing study.