scope:

This Technical Report provides a literature survey about the human-machine interface of warning systems in vehicles, including studies of ISO/TC 22/SC 13/WG 8 and ISO/TC 204/WG 14. It covers the experimental experiences about the efficiency and acceptance of different modalities and combinations of warnings, and the design of the sensorial, code and organizational parameters of visual, auditory and tactile warnings (as well as concluding recommendations). The survey should initialize standardizing activities of ISO working groups, e.g. ISO/TC 22/SC 13/WG 8. This literature survey comprises the human-machine interface issues of warning systems in automobiles. The discussion of warning signals in general is dealt with in Clause 2 and concerns the definition of warning signals, their failure and urgency aspects. Alarm theories are briefly dealt with here. The basic psychological and physiological aspects of warnings in vehicles are the subject of Clause 3. Some issues of human behaviour, which are relevant to handling warnings, are described. Due to their importance, the sensorial modalities are introduced separately in Clause 4. Auditory and tactile presentations are becoming more and more important, which is reflected in the structure of the next three Clauses 5, 6 and 7. The specific psychological and physiological bases, benefits and types of displays for each sensory modality are presented in these clauses. Clause 5 is dedicated to visual warning displays with a few examples of the sensorial-related parameters. Symbols, icons and text are discussed extensively. Other coding and organizational features are handled as far as warning signals are affected (colour, blinking, structures, etc.). Clause 6 is dedicated to auditory warning displays. The basic differences and the respective benefits of tonal signals, auditory icons and speech output are explained. This is the largest clause because of its significance for oncoming information and warning systems in cars. The display parameters, which are particularly relevant for auditory warning signals, are presented in more detail, i.e. startling effect, temporal and spatial characteristics. The new auditory icons are elaborated more in detail because of their relevance for collision warning systems. The sensorial, coding and organizational parameters of speech output are described in a comprehensive manner. Clause 7 is dedicated to tactile warning displays. Although the potential of tactile warnings has been clearly demonstrated, data for their design is very scarce. The redundant presentation of warnings is described in Clause 8. The experimental results of different visual/auditory combinations are presented, as well as visual/auditory/tactile combinations. The possible transfer of master alertings from the avionic environment into the automobile environment is discussed. Other concepts like the graded sequence of warnings are included. The experimental results with different warning signals and their combinations are presented in Clause 9 with respect to type, code and modality of the warnings. The benefits of visual, auditory and tactile warnings depend on whether objects, spatial relations or abstract information are transmitted verbally or non-verbally. A series of field experiments with symbolic, written, tonal, spoken and tactile warnings are reported. Clause 10 includes some of the assistance systems that have just been introduced, such as distance warning systems, or that are about to be introduced, such as side-obstacle warning systems. All of these are relatively time-critical and need carefully designed warnings with a particular emphasis on auditory and tactile displays. The recent experimental results are cited. In Clause 11, warning systems in other domains, especially avionics, are described. The extensive experiences with the problems of several time-critical alarms in aircrafts as well as the flood of alarms in power plants will be exemplified. Clause 12 is dedicated to the discussion of the previous clauses and their relevance for warnings in vehicles.