# The Application of Augmented Reality in the Automotive Industry: A Systematic Literature Review
## 4 Discussion  
The first research question sought to identify the application area and the purpose of the developed AR systems. In this regard, the papers are first divided in two categories: 'in-car' AR systems developed for improving user experience and other AR systems which are linked to the automotive field. Four areas where identified for the second category: manufacturing, maintenance, design and assembly. AR has been found to have great potential for application in many industrial operations in the automotive field, especially for the assistance and training of operators, but also in certain aspects related to ergonomics. This is important because the factors related to efficiency (usage time, cognitive workload) and physical comfort are essential when working with AR systems [85]. Regarding the systems developed for driver assistance, a large majority of studies focus on the display interface. This is somewhat understandable as it is very important that AR elements are presented in such a manner that they do not obscure the driver's view of the road in order to prevent the potential dangers that may occur while driving [22]. Other issues discussed are some technical details regarding the development and implementation of AR systems for driver assistance, as well as aspects related to safety and to the upcoming technology that will revolutionize the future of driving and vehicle-to-vehicle communication. The general characteristics of AR systems were identified in an effort to respond to the second research question. The technological solutions for visualization used in the analyzed papers are mainly handheld devices (smartphones and tablets), HMDs and AR smart glasses. The main advantages that these devices bring to the AR applications are ease of use, portability and various ways of implementation. There has been a growing trend of mobile devices and glasses usage in recent years, which is explained by the following facts: handheld devices have the advantage of low cost and simplicity in creating applications, they are more suitable for maintenance tasks, and smart glasses are suitable for tasks where the user has busy hands, such as assembly. Projector-based systems are developed mainly for manufacturing and design tasks to display 3D information on the workspace. HMDs also represent a solution, but they depend on computers or do not allow high resolution graphics [86]. In addition, ergonomics issues have been discussed in connection with HMDs [21], but these as well as technical problems will be overcome with the evolution of hardware and software technology [87]. The analysis of the tracking technology revealed that there is approximate equality between marker-based and markerless solutions, with a slight advantage of the former. This could be a consequence of the fact that marker-based solutions are easier to implement and provide better accuracy, as found in [21]. Regarding the systems designed for 'in-car' use, some studies are based on commercial HUDs, and a smaller percentage of them use HUDs designed 'in-house'. Many studies are trying to improve aspects of user interaction, but there is still a need for research related to HMI and human factors [23]. In the analyzed studies various types of information that are overlapping elements in the work environment were presented: text, images, 3D graphics and animations. They can be classified into five groups, as stated in [9]. In addition to this information regarding visual perception, some studies have presented a combination of other elements with the visual ones in order to stimulate audio and tactile perception. From the whole sample of evaluated articles, less than half used user studies to validate the research, and most of them used a subjective evaluation by collecting data through questionnaires or interviews. For statistical analysis, the vast majority of studies used the ANOVA technique.