More than 1.3 million people lose their lives every year in traffic accidents. Improving road safety requires designing better vehicles and investigating drivers’ abilities more closely. Driving simulators are constantly being used for this purpose, but the question which often arises as to their validity tends to be a barrier to developments in this field. Here we studied the validity of a simulator, defined as how closely users’ behavior under simulated conditions resembles their behavior on the road, based on the concept of drivers’ feeling of presence. For this purpose, the driving behavior, physiological state and declarative data of 41 drivers were tested in the Sherpa2 simulator and in a real vehicle on a track while driving at a constant speed. During each trial, drivers had to cope with an unexpected hazardous event (a one-meter diameter gym ball crossing the road right in front of the vehicle), which occurred twice. During the speed-maintenance task, the simulator showed absolute validity, in terms of the driving and physiological parameters recorded. During the first hazardous event, the physiological parameters showed that the level of arousal (Low Heart Rate/High Heart Rate ratio x10) increased up to the end of the drive. On the other hand, the drivers’ behavioral (braking) responses were 20% more frequent in the simulator than in the real vehicle, and the physiological state parameters showed that stress reactions occurred only in the real vehicle (+5 beats per minute, +2 breaths per minute and the phasic skin conductance increased by 2). In the subjects’ declarative data, several feeling of presence sub-scales were lower under simulated conditions. These results suggest that the validity of motion based simulators for testing drivers coping with hazards needs to be questioned.

Car manufacturers expect driving simulators to be reliable research and development tools. Questions arise, however, as to whether drivers? behavior on simulators exactly matches that observed when they are driving real cars. Drivers? performances and their subjective feelings about their driving were compared between two groups during a 40-min driving test on the same circuit in a real car (n = 20) and a high-fidelity dynamic simulator (n = 27). Their speed and its variability, the braking force and the engine revolutions per minute (rpm) were recorded five times on a straight line and three times on a curve. The differences observed in these measurements between circuit driving (CD) and simula-tor driving (SD) from the 6th to 40th minute showed no significant changes during the drive. The drivers also completed the NASA Raw Task Load Index (NASA RTLX) question-naire and the Simulator Sickness Questionnaire (SSQ) and estimated the ease and standard of their own driving performances. These subjective feelings differed significantly between the two groups throughout the experiment. The SD group?s scores on the NASA RTLX and SSQ questionnaires increased with time and the CD group?s perceived driving quality and ease increased with time, reaching non-significantly different levels from their usual car driving standards by the end of the drive. These findings show the existence of a fairly good match between real-life and simulated driving, which stabilized six minutes after the start of the test, regardless of whether the road was straight or curved. These objective findings and subjective assessments suggest possible ways of improving the match between dri-vers? performances on simulators and their real-life driving behavior. ? 2021 Elsevier Ltd. All rights reserved.

Conditionally automated driving (SAE Level 3) relinquishes driver from monitoring the driving task and the traffic environment, permitting the driver to perform non-driving-related tasks (NDRT). Nevertheless, the driver must be available as a backup option. With this in mind, the current study aims at investigating the effect of the type of NDRT and takeover situations on driver performance. The NDRTs used were writing emails and watching videos, while the takeover situations tested were avoiding an obstacle on one's lane and missing lane markings. Forty-four participants took part in a study carried in a dynamic simulator at PSA Peugeot Citroen Technical Center. Results showed that an effect of takeover situation on takeover time, with shorter times associated with obstacle avoidance, regardless of the type of NDRT. Measures of driver performance in the obstacle avoidance situation did not differ among manual and automated driving conditions, except for minimum time to collision. In the missing lane conditions, an effect of driving mode was observed on lateral and longitudinal control, as well as minimum time headway, regardless of the type of NDRT was observed. Our results suggest that the criticality of the situation had a distinct effect on takeover time and mental workload, while NDRT did not have a clear role. Furthermore, in line with previous research, drives' need for control stabilization beyond takeover was documented. (C) 2019 Published by Elsevier Ltd.

Using modern advanced driving simulator for human factors research has many advantages such as experimental control, expense, safety, and ease of data collection. However, the literature describes some possible disadvantages, i.e. simulator sickness, inaccurate replication of physical sensations, and most importantly, validity, which is the extent to which human behavior observed in simulation conditions, can be generalized to real situations. In other words, whereas physical validity is improving, psychological and behavioral validity remains a difficult problem. Assessing the absolute validity of driving simulation would require the comparison of results obtained from studies conducted in a real situation and in a virtual environment. However, this comparison is expensive (instrumentation) and complex, if possible (strict control of all the events occurring in a real situation). One way to deal with this problem is to focus on relative behavioral validity, trying to evaluate to what extent human behavior observed in simulation conditions is qualitatively similar to a "real world" behavior. A correlative approach is to try to measure, by manipulating experimental conditions, to what extent this behavior is modified, with reference to a "real world" behavior. This is typically what the concept of presence, introduced in virtual reality research to describe psychological and behavioral effects of immersive virtual environments, tries to achieve.

This pilot study aims to find a way to measure ‘presence’ as a proxy for ecological validity in driving simulators. The underlying assumption is that a person experiencing a strong sense of presence in the virtual environment will react as if it were real. We measure ‘presence’ through the ‘attention’ given to the driving task. We hypothesize that the greater the attention given to the primary driving task, the more the subject will experience spatial presence. ‘Attention’ was varied by adding a second task and oncoming traffic; we then analyzed behavioral measures of driving performance and subjective ‘presence’. The main result is a lack of congruence between subjective and behavioral measures. Although behavioral differences were observed between the various experimental conditions, there was no significant difference in subjective measures of presence. One explanation for this result could be that in all experimental conditions the driving activity did not require high-level cognitive processes, and was instead based on bottom-up attentional processes. Many of the processes involved in driving seem to be automatic, and this study argues for the concomitant use of subjective measures (such as questionnaires) and objective measures to assess presence in driving simulators. Furthermore, the development of a sensitive measure of presence seems to require more challenging scenarios in terms of controlled attention, cognitive involvement and more specifically, the emotions induced by the media. Participants are clearly aware that they are not exposed to any physical danger when using the simulator and the problem of their motivation must be taken into consideration. Another major problem is to establish the extent to which they are absorbed in the simulated driving task. A significant challenge for future research is the emotional validity of driving.

In this paper, our ambition is to find a way of measuring “presence” to use it as a measure for ecological validity in driving simulators. The underlying assumption is that a person experiencing a strong sense of presence in the virtual environment will react in this environment as if it would be a real one. We propose to measure "presence" by measuring “attention” toward the driving task". Our objective is to demonstrate that the higher the subject's attention required by the primary driving task will be, the more the spatial presence will be felt. In the experiment we tried to vary "attention" by adding a dual task and by adding traffic and measure driving performance and subjective "presence". The main result is a lack of congruence between subjective and behavioral measures.

The main contribution of this paper to the Cognitive Ergonomics field is to propose a new approach of the behavioral validity's assessment of driving simulators. In this paper, our ambition is to find a way of measuring “presence” to use it as a measure for ecological validity in driving simulators. In this way, the purpose of this study is especially to investigate the relationship between subjective ratings of presence and physiological responses in virtual driving environments. Six driving scenarios were, thus, created, resulting from crossing two independent variables, i.e., the visual realism of the virtual environment (three virtual environments were created ranging from very realistic to not realistic) and the degree of visibility on the road for each virtual environment (two conditions were proposed : very good visibility and very bad visibility). Whatever the scenario, the driving task was always to follow a red car without losing sight of its location. To measure subjective presence, attention and emotional involvement, Presence, and Mood questionnaires were used. As measures of physiological response, heart rate and skin conductance level were acquired and more specifically the heart rate variability (HRV) was calculated from the acquired ECG data. Driving performance (standard deviations of speed and lateral position) was also analyzed. Fourteen participants (25.4±4.5 years of age) were placed in a fixed base driving simulator and performed consecutively the six driving scenarios in a different order. The results show correlations between Presence Questionnaire scores and both HRV parameters (time and frequency domains) and skin conductance level. In the study, HRV parameters and skin conductance level appeared to indicate the participant's degree of presence.

The present study investigates the importance of lateral acceleration, roll angle and yaw acceleration as scale factors (motion gains) on these components, in the driving perception and behavior in curve. Recent study advises to use down scale-factors (0.4-0.75) on the three car lateral motions felt in curve. In the current study, we used the same slalom task, and increased the range of lateral acceleration produced by the slalom, as the scale factors. The principal result is that the lateral motion gain has to decrease with the increase of lateral acceleration, in order to improve the perception and the driving performance. Concerning the roll motion gain, we advise to use it with a unit gain whether the quantity of lateral acceleration. However, the important of yaw motion is more controversial, it only seems to facilitate the driving control, at less in this slalom task.