Abstract
The aim of this review is to identify how visual occlusion contributes to our understanding of attentional demand and spare visual capacity in driving and the strengths and limitations of the method. The occlusion technique was developed by John W. Senders to evaluate the attentional demand of driving. Despite its utility, it has been used infrequently in driver attention/inattention research. Visual occlusion studies in driving published between 1967 and 2020 were reviewed. The focus was on original studies in which the forward visual field was intermittently occluded while the participant was driving. Occlusion studies have shown that attentional demand varies across situations and drivers and have indicated environmental, situational, and inter-individual factors behind the variability. The occlusion technique complements eye tracking in being able to indicate the temporal requirements for and redundancy in visual information sampling. The proper selection of occlusion settings depends on the target of the research. Although there are a number of occlusion studies looking at various aspects of attentional demand, we are still only beginning to understand how these demands vary, interact, and covary in naturalistic driving. The findings of this review have methodological and theoretical implications for human factors research and for the development of distraction monitoring and in-vehicle system testing. Distraction detection algorithms and testing guidelines should consider the variability in drivers' situational and individual spare visual capacity.
Highlights
The visual occlusion technique was developed by Senders et al (1967) to evaluate attentional demand in driving
Occlusion studies have shown that attentional demand varies across situations and drivers and have indicated environmental, situational, and inter-individual factors behind the variability
The main objective of the experiment, the number of participants, the driving environment, and the settings of the occlusion experiment are provided. The latter includes the mechanisms used to operate the occlusion device, ranging from finger or foot operated switches/pedals (Figure 2) to closing one’s eyes, and the occlusion area, which can consist of the entire visual field or its central parts
Summary
The visual occlusion technique was developed by Senders et al (1967) to evaluate attentional demand in driving. The occlusion technique can be used to evaluate the analog but opposing concept of “spare visual capacity,” which measures the fraction of time that the driver’s visual field is occluded (Safford, 1971). These fractions can inform about the required (visual) information sampling frequency in driving. This understanding is important for defining safe attention allocation behaviors in traffic for scientific, engineering and regulatory purposes. It has been used infrequently in driver attention/inattention research
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