During the past decades there has been an extensive evolution in computer and communication technologies. In the last ten years these technologies have become an integrated part of our cars via in-vehicle information systems. Considerable efforts are put into research and development of the interface between the in-vehicle information systems and the driver. Due to the fact that vision is imperative in driving, the focus is in particular on the visual-manual interface and on apt usability evaluation methods.The purpose of this thesis is to study design implications for the development of visual-manual interfaces in cars. A point of departure is that the practice of the usability concept, usability evaluation methods, and compliance tests has implications for the design process.Four papers are appended to the thesis. Paper I focuses on differences between rotary control and touch screen interfaces in terms of driving simulator and glance metrics. Paper II investigates correlations between data from customer evaluations and expert evaluations for visual-manual interfaces. Paper III searches for the presence of and possible explanations for individual glance strategies in a driving simulator study. Paper IV investigates effects of individual glance strategies on the NHTSA visual-manual distraction test in a driving simulator set-up.In the thesis it is concluded that the optimal input device is dependent on the task being performed, that is, the touch screen is more efficient for alphanumeric input while rotary control performs list scrolling more efficiently. In addition, drivers seem to adapt their glance behaviour based on the display position. It is evident that efficiency metrics correlate between several usability evaluation methods. Hence, it is possible to generalise results from expert evaluations at an early design phase, to customer survey samples based on car ownership. Concerning glance behaviour, it is clear that individual glance strategies exist. Especially interesting are two glance strategies, long glancers and frequent glancers, that affect the results of the NHTSA compliance testing. These glance strategies have to be controlled for in the test situation. Finally, a framework is proposed that combines a classification of visual-manual actions with different visual fixations. The task analysis framework has the potential to analyse actions in terms of required visual resources, thus already providing an evaluation of visual-manual interfaces in the concept phase.

The purpose of this paper was to investigate how individual differences in glance strategy could impact the glance performance test defined in the NHTSA visual manual distraction guidelines. Better understanding of the test procedure could help development of new technology for safe driving. A custom in-vehicle information system was developed and assessed in a driving simulator by eighteen participants. The interfaces were designed according to recommendations in the NHTSA guidelines and contained manual radio-tuning tasks, sound settings tasks and six letter spelling tasks. Two of the six tested interfaces fully complied with the test. In addition, clear individual differences in glance strategy were found among the participants. Four individual glance strategies were identified. Two of these, long glancers and frequent glancers, highly affected the outcome of the compliance test. Participants belonging to the long glancers and the frequent glancers categories were identified as statistical outliers in many test cases. For example, if the individual values of these participants were replaced with sample mean, the number of complying interfaces would increase to five out of six, which is more in line with expectations for these interfaces. The results of this study show that individual variations in glance strategy exist. Also, these individual variations seem to have a non- negligible influence on the result when performance-testing of in-vehicle interfaces is done according to the NTHSA guidelines.

With the functional revolution in modern cars, evaluation methods to be used in all phases of driver-car interaction design have gained importance. It is crucial for car manufacturers to discover and solve safety issues early in the interaction design process. A current problem is thus to find a correlation between the formative methods that are used during development and the summative methods that are used when the product has reached the customer. This paper investigates the correlation between efficiency metrics from summative and formative evaluations, where the results of two studies on sound and navigation system tasks are compared. The first, an analysis of the J.D. Power and Associates APEAL survey, consists of answers given by about two thousand customers. The second, an expert evaluation study, was done by six evaluators who assessed the layouts by task completion time, TLX and Nielsen heuristics. The results show a high degree of correlation between the studies in terms of task efficiency, i.e. between customer ratings and task completion time, and customer ratings and TLX. However, no correlation was observed between Nielsen heuristics and customer ratings, task completion time or TLX. The results of the studies introduce a possibility to develop a usability evaluation framework that includes both formative and summative approaches, as the results show a high degree of consistency between the different methodologies. Hence, combining a quantitative approach with the expert evaluation method, such as task completion time, should be more useful for driver-car interaction design.

In the past ten years information and entertainment functionality has become an increasingly important part of the car interior. Infotainment functions have been growing in number and diversity, concurrently with a trend towards utilization of fewer controls and graphical displays in integrated centre panel layouts. This evolution has solved many functional and styling issues. However, as a consequence, several usability and safety concerns have been raised. A number of these concerns are related to age, a factor that is especially important in the premium car segment where a majority of drivers are older than 50 years. This study investigated perceived styling and usability of premium car centre panel layouts among different age groups. The investigation was based on APEAL customer survey data from the North American market, associated with the sound system. Questions on the appearance (styling), understanding (usability) and ease of use while driving (usability/safety) of the stereo faceplate and controls were analysed. The results showed that all age groups perceived the appearance of integrated centre panel layouts similarly. However, with rising age, there is a decrease in perceived understanding and ease of use while driving in the case of a number of premium car models.

Driving behaviour has been less documented than driver workload. The possibilities to define a framework that could be part of a driving behaviour model were investigated. The results present a framework that defines twelve scenarios in which drivers have misinterpreted a driving situation. The descriptions show evidence of increased user experience for some scenarios while other indicates reduced traffic safety. The results suggest that by using the framework-descriptions on how and why mismatches occur, design guidelines for in-vehicle systems can be developed.

Over the last years active safety has become an increasingly important factor within the automotive industry. Active safety systems, also known as Advanced Driver Assistance Systems (ADAS), have the function of actively assisting the driver in avoiding accidents by providing information about current and upcoming traffic situations and helping the driver take proper actions before a potential accident occurs. In this paper, differences and similarities in attitude towards three different ADAS were investigated. A set of three focus group discussions were conducted with Swedish, US American, and Chinese participants. The analysis of subjective data showed differences between the three groups regarding attitudes towards system feasibility, information presentation and need for system adjustability. Results also showed that factors such as driving conditions, infrastructure, and traffic regulations all seemed to influence the hypothesised usefulness of the different systems.

Car Human-Machine Interaction (HMI) is becoming increasingly complex as the extension of functionality necessitates new interface concepts. Various multifunctional systems operated by haptic rotary switches, touch screen, and voice control have been developed. A usability study of multifunctional systems available on the market was carried out to evaluate and compare different manual interaction principles. The systems used in the study were the BMW iDrive and the Audi MMI, both operated by a rotary switch, and the Jaguar touch screen interface. Firstly, a usability test was conducted where two naive and two trained participants tested each system during driving. Ten tasks, comprising CD, radio and navigation were solved by the participants. Secondly, six evaluators carried out a usability inspection, heuristic evaluation, to find possible problems in the systems. The results from the usability test indicated that the naive users interacted more rapidly with the touch screen interface. Trained users, on the other hand, had more even results over the systems. The problems found in the usability inspection gave explanations to some of the longer task times in the usability test.

A driving simulator study was conducted to investigate the effects of carrying out a variety of tasks using two different types of contemporary in-car multifunctional interfaces: a touch screen interface and an interface manoeuvred by a rotary control. Participants drove on a curved rural road while performing tasks such as list scrolling, radio tuning, alphanumeric input and continuous adjustments. The results indicate that, in terms of task completion time and the number of glances made to the display, the optimal interface is dependent on the task being performed. The touch screen interface was better for alphanumeric input tasks and the interface manoeuvred by a rotary control was better for continuous adjustments and list scrolling. Alphanumeric input seems to be more demanding than other tasks, independent of the interface used. It was apparent in this simulator study that both interfaces affected the lateral control performance, but lateral control performance deteriorated to a greater extent when the touch screen interface was used, probably partially as a result of the lower display position.

A driving simulator study was conducted to investigate whether the interaction with an in-vehicle multifunctional interface maneuvered by a rotary control can be improved if assisting haptics is provided. Two conditions were compared in the study, one in which neutral haptics was provided through the rotary control and one in which enhanced haptics was provided. Participants drove on a curved rural road while performing tasks such as list scrolling, radio tuning and text entry. The results indicated that, for radio tuning and settings adjustments tasks, interaction is improved when enhanced haptics is provided. It was shown that enhanced haptics can increase performance in terms of task completion time and can reduce the number and duration of glances made to the display. However, for alphanumeric input tasks, improvements are needed. Enhanced haptics seems to facilitate interaction with functions in which the sensations can be incorporated in an intuitive way.