Assisting the older driver: intersection design and in-car devices to improve the safety of the older driver

This doctoral thesis is concerned with the possibilities offered by road design and driver assistance systems to improve older adults' safe and independent mobility by compensating for their age-related functional limitations. The main research questions of this thesis relate to a general description of the current and future safety of older drivers, the characteristics of older drivers that may influence their safety, the most important needs for support that result from these characteristics, and assistive devices that may provide the desired support. Analogous to these research questions, this doctoral thesis can be divided into three main sections. Chapters 1 and 2 relate to the first question. In Chapter 1, the safety of older drivers is described based on crash and injury data for the Netherlands. Their current fatality and injury rates are discussed, as well as the underlying factors which determine the level of these rates. Furthermore, the crash types which prevail among older drivers are described. In Chapter 2, the physical and mental qualities of older adults are described, as well as the way in which they can influence driver performance. Chapter 3 closes the first section of this thesis. In this chapter, factors are discussed that may influence future crash and injury rates for older drivers, as well as measures which can be taken to reduce these rates. Chapter 4 addresses the second question. In this chapter, the physical and mental qualities of older adults are discussed from a theoretical perspective. The aim of this chapter is to identify the relative weaknesses of the older driver, as it is assumed that specific measures will be most capable of reducing the crash involvement of older drivers if they support these weaknesses of the driver. With this aim, the strengths and weaknesses of older drivers are deduced from the literature that originates from several theoretical perspectives on human functioning: Fuller’s task-capability interface model, the human factors approach, cognitive psychology, and game theory. The result is a list of the relative weaknesses of the older driver and the difficulties that older drivers encounter in traffic as a result of these weaknesses. To be able to rate the relevance of these weaknesses to road safety, the weaknesses are compared with crash data. Those weaknesses that have a substantial influence on road safety, as indicated by the percentage of crashes that could have been avoided if the weakness would not have existed (or would have been compensated for by, for example, ADAS), are considered to indicate a need for support. The result is a shortlist of desired types of support. In the third section (chapters 5 to 8), the focus is on road design and in-car driver assistance systems as devices which may offer the desired types of support. In the first two chapters of this section, chapters 5 and 6, the focus is on measures concerning road design. To find leads for road design elements that put the older driver to the test, Chapter 5 starts with an analysis of the differences between intersections at which many and those at which few crashes occur involving older drivers. Following on that, adjustments to road design are discussed which take into account the limitations of older drivers, and which for that reason appear to offer the desired types of support mentioned in chapter 4. In Chapter 6, the results are described of a simulator study in which several types of intersection designs were compared on their effects on driver workload and driver behaviour. In chapters 7 and 8, the focus is on driver assistance systems that may offer the desired types of support. In Chapter 7, specific types of in‐car driver assistance systems are described that appear to offer the desired types of support. In addition, it is discussed which conditions assistance systems should meet to actually improve the safety of older drivers. Topics included are user acceptance, design requirements for the human-machine interface, and prevention of negative side-effects. In Chapter 8, the results are described of a simulator study in which one specific driver assistance system was tested for its effects on driver workload and driver behaviour. Finally, in the last part of this thesis, the main findings are summarized and conclusions are drawn about the role that road design and in‐car driver assistance systems can play in compensating for functional limitations.