Driving simulators are established tools used during automotive development and research. Most simulators use either monitors or projectors as their primary display system. However, the emergence of a new generation of head-mounted displays has triggered interest in using these as the primary display type. The general benefits and drawbacks of head-mounted displays are well researched, but their effect on driving behavior in a simulator has not been sufficiently quantified. This article presents a study of driving behavior differences between projector-based graphics and head-mounted display in a large dynamic driving simulator. This study has selected five specific driving maneuvers suspected of affecting driving behavior differently depending on the choice of display technology. Some of these maneuvers were chosen to reveal changes in lateral and longitudinal driving behavior. Others were picked for their ability to highlight the benefits and drawbacks of head-mounted displays in a driving context. The results show minor changes in lateral and longitudinal driver behavior changes when comparing projectors and a head-mounted display. The most noticeable difference in favor of projectors was seen when the display resolution is critical to the driving task. The choice of display type did not affect simulator sickness nor the realism rated by the subjects.

In the last decades, there has been a substantial increase in the development of complex active safety systems for automotive vehicles. These systems need to be tested for verification and validation to ensure that the system intervenes in the correct situations using the correct measures. There are multiple methods available to perform such testing. Software-in-the-loop and hardware-in-theloop testing offer effective driverless testing. Other methods increase the fidelity by including human drivers, such as driving simulators and experiments performed at test tracks.This thesis examines vehicle-in-the-loop testing, an innovative method where the driver of a real vehicle wears a head-mounted display that displays virtual targets. This method combines the benefits of driving simulators with the benefits of using a real vehicle on a test track. Driving simulators offer repeatability, safety, and the possibility of complex interactions between actors. In contrast, the real vehicle provides the correct vehicle dynamics and motion feedback.There is a need to know how the technology behind the method might influence the results from vehicle-in-the-loop testing. Two techniques for vehicle-in-the-loop systems are studied. The first involves video-see through head-mounted displays, where the focus of the research is on the effects of visual latency on driving behavior. The results show that lateral driving behavior changes with added latency, but longitudinal behavior appears unaffected. The second system uses an opaque head-mounted display in an entirely virtual world. The research shows that this solution changes speed perception and results in a significant degradation in performance of tasks dependent on visual acuity.This research presents results that are relevant to consider when developing vehicle-in-the-loop platforms. The results are also applicable when choosing scenarios for this test method.

Using mixed reality in vehicles provides a potential alternative to using driving simulators when studying driver-vehicle interaction. However, virtual reality systems introduce latency in the visual system that may alter driving behavior, which, in turn, results in questionable validity. Previous studies have mainly focused on visual latency as a separate phenomenon. In this work, latency is studied from a task-dependent viewpoint to investigate how participants’ driving behavior changed with increased latency. In this study, the investigation was performed through experiments in which regular drivers were subjected to different levels of visual latency while performing a simple slalom driving task. The drivers’ performances were recorded and evaluated in both lateral and longitudinal directions along with self-assessment questionnaires regarding task performance and difficulty. All participants managed to complete the driving tasks successfully, even under high latency conditions, but were clearly affected by the increased visual latency. The results suggest that drivers compensate for longer latencies by steering more and increasing the safety margins but without reducing their speed.

When developing new active safety systems or improving existing systems, conducting performance evaluations is necessary. By performing these evaluations during early development stages, potential problems can be identified and mitigated before the system moves into the production phase.Testing active safety systems can be difficult since the characteristic scenarios may have complex interactions. Using real vehicles for performing these types of scenarios is difficult, expensive, and potentially dangerous. Alternative methods, such as using inflatable targets, scale models, computer simulations or driving simulators, also suffer from drawbacks. Consequently, using virtual reality as an alternative to the traditional methods has been proposed. In this case, a real vehicle is driven while wearing a head-mounted display that presents the scenario to the driver.This research aims to investigate the potential of such technology. Specifically, this work investigates how the chosen technology affects the driver. This investigation has been conducted through a literature review. A test platform was constructed, and two user studies using normal drivers were performed. The first study focused on the effects of visual time delays on driver behavior. This study revealed that lateral behavior changes with added time delays, whereas longitudinal behavior appears unaffected. The second study investigated how driver behavior is affected by different modes of virtuality. This study demonstrated that drivers perceived mixed reality as more difficult than virtual reality.The main contribution of this work is the detailed understanding of how time delays and different modes of virtuality affect drivers. This is important knowledge for selecting which scenarios are suitable for evaluation using virtual reality. Keywords PapersThe following four appended papers are arranged in chronological order of publication and will be referred to by their Roman numerals. All papers are printed in their original published state with the exception of minor errata and changes in text and figure layout in order to maintain consistency throughout the thesis. In papers [I], [II], [III] and [IV], the first author is the main author, responsible for the work presented, with additional support from the co-authors. A short summary of each paper can be found in chapter 4.[I] Björn Blissing, Fredrik Bruzelius, and Johan Ölvander." [VIII] Lars Eriksson, Lisa Palmqvist, Jonas Andersson Hultgren, Björn Blissing, and Steven Nordin. "Performance and presence with head-movement produced motion parallax in simulated driving".

This paper presents a comparative study of driving behavior when using different virtual reality modes. Test subjects were exposed to mixed, virtual, and real reality using a head mounted display capable of video see-through, while performing a simple driving task. The driving behavior was quantified in steering and acceleration/deceleration activities, divided into local and global components. There was a distinct effect of wearing a head mounted display, which affected all measured variables. Results show that average speed was the most significant difference between mixed and virtual reality, while the steering behavior was consistent between modes. All subjects but one were able to successfully complete the driving task, suggesting that virtual driving could be a potential complement to driving simulators.