Christhard Gelau

Risk perception and age-specific accidents of young drivers

Accident risk involved in 100 slide-presented traffic situations was rated by 208 male and 100 female drivers in the age groups 18-21, 35-45, and 65-75 years. The main finding is that young male drivers rated the traffic situations as less risky than did older male drivers. This was especially the case for situations involving the following aspects: darkness, inclining/declining or curved roadways, and rural environment. No comparable age effect was present for females. These findings are in agreement with findings from accident studies, showing overinvolvement of young males in single-vehicle accidents that are characterized by the above mentioned aspects. The results show that educational measures for young drivers should emphasize different aspects for young men and young women and especially that young mens risk perception (as well as their risk tolerance) in those situations mentioned above must be made part of further efforts.

The influence of cruise control and adaptive cruise control on driving behaviour--a driving simulator study.

Although Cruise Control (CC) is available for most cars, no studies have been found which examine how this automation system influences driving behaviour. However, a relatively large number of studies have examined Adaptive Cruise Control (ACC) which compared to CC includes also a distance control. Besides positive effects with regard to a better compliance to speed limits, there are also indications of smaller distances to lead vehicles and slower responses in situations that require immediate braking. Similar effects can be expected for CC as this system takes over longitudinal control as well. To test this hypothesis, a simulator study was conducted at the German Aerospace Center (DLR). Twenty-two participants drove different routes (highway and motorway) under three different conditions (assisted by ACC, CC and manual driving without any system). Different driving scenarios were examined including a secondary task condition. On the one hand, both systems lead to lower maximum velocities and less speed limit violations. There was no indication that drivers shift more of their attention towards secondary tasks when driving with CC or ACC. However, there were delayed driver reactions in critical situations, e.g., in a narrow curve or a fog bank. These results give rise to some caution regarding the safety effects of these systems, especially if in the future their range of functionality (e.g., ACC Stop-and-Go) is further increased.

On the reliability of the occlusion technique as a tool for the assessment of the HMI of in-vehicle information and communication systems

In recent years considerable efforts have been spent on the development of the occlusion technique as a procedure for the assessment of the human-machine interface of in-vehicle information and communication systems (IVIS) designed to be used by the driver while driving. The importance and significance of the findings resulting from the application of this procedure depends essentially on its reliability. Because there is a lack of evidence as to whether this basic criterion of measurement is met with this procedure, and because questionable reliability can lead to doubts about their validity, our project strove to clarify this issue. This paper reports on a statistical reanalysis of data obtained from previous experiments. To summarise, the characteristic values found for internal consistency were almost all in the range of .90 for the occlusion technique, which can be considered satisfactory.

Skill acquisition while operating in-vehicle information systems: interface design determines the level of safety-relevant distractions.

Objective: This study tested whether the ease of learning to use human—machine interfaces of in-vehicle information systems (IVIS) can be assessed at standstill. Background: Assessing the attentional demand of IVIS should include an evaluation of ease of learning, because the use of IVIS at low skill levels may create safety-relevant distractions. Method: Skill acquisition in operating IVIS was quantified by fitting the power law of practice to training data sets collected in a driving study and at standstill. Participants practiced manual destination entry with two route guidance systems differing in cognitive demand. In Experiment 1, a sample of middle-aged participants was trained while steering routes of varying driving demands. In Experiment 2, another sample of middle-aged participants was trained at standstill. Results: In Experiment 1, display glance times were less affected by driving demands than by total task times and decreased at slightly higher speed-up rates (0.02 higher on average) than task times collected at standstill in Experiment 2. The system interface that minimized cognitive demand was operated more quickly and was easier to learn. Its system delays increased static task times, which still predicted 58% of variance in display glance times compared with even 76% for the second system. Conclusion: The ease of learning to use an IVIS interface and the decrease in attentional demand with training can be assessed at standstill. Application: Fitting the power law of practice to static task times yields parameters that predict display glance times while driving, which makes it possible to compare interfaces with regard to ease of learning.

Maximization of subjective expected utility or risk control? Experimental tests of risk homeostasis theory

Valid and meaningful studies examining the risk homeostasis theory (RHT) not only have to be experimental; they also have to be able to make predictions specific to this theory. Generally this is not true for earlier studies. Therefore two experiments were developed for which the theory of the maximization of the subjective expected utility (SEU-model) and the risk homeostasis theory (RHT) make different predictions. In the first experiment, a computer simulation of an intersection situation, forty subjects were asked to move as many vehicles as possible across an intersection making use of the gaps in the flow of traffic while avoiding collisions with the crossing traffic. As a within-subjects-factor the level of difficulty of the task was varied by changing the number of suitable gaps in the moving traffic. Subjects could react either by changing the number of crossings and/or the number of collisions. The between-subjects-factor, the variation of the relative size of the reward for a successful crossin...

Predicting the acceptance of advanced rider assistance systems

The strong prevalence of human error as a crash causation factor in motorcycle accidents calls for countermeasures that help tackling this issue. Advanced rider assistance systems pursue this goal, providing the riders with support and thus contributing to the prevention of crashes. However, the systems can only enhance riding safety if the riders use them. For this reason, acceptance is a decisive aspect to be considered in the development process of such systems. In order to be able to improve behavioural acceptance, the factors that influence the intention to use the system need to be identified. This paper examines the particularities of motorcycle riding and the characteristics of this user group that should be considered when predicting the acceptance of advanced rider assistance systems. Founded on theories predicting behavioural intention, the acceptance of technologies and the acceptance of driver support systems, a model on the acceptance of advanced rider assistance systems is proposed, including the perceived safety when riding without support, the interface design and the social norm as determinants of the usage intention. Since actual usage cannot be measured in the development stage of the systems, the willingness to have the system installed on the own motorcycle and the willingness to pay for the system are analyzed, constituting relevant conditions that allow for actual usage at a later stage. Its validation with the results from user tests on four advanced rider assistance systems allows confirming the social norm and the interface design as powerful predictors of the acceptance of ARAS, while the extent of perceived safety when riding without support did not have any predictive value in the present study.

Evaluating visual display designs in vehicles: Advantages and disadvantages of the occlusion technique

Over the last few years the amount of in-car visual displays has steadily increased. Despite of positive aspects of additional systems it is important to make these systems as safety as possible. A method to evaluate the design objectives of quick and reliable information acquisition is the occlusion technique. In this paper we describe the technique and report experimental results from several evaluation studies. We found that the occlusion technique reliably discriminates between simple and complex visual displays. We also found that the occlusion technique reliably discriminates between dialogues that facilitate resumption after an interruption and those that do not. The implications of these results and the applicability of the method are discussed.