title: The Attentional Demand of Automobile Driving Revisited: Occlusion Distance as a Function of Task-Relevant Event Density in Realistic Driving Scenarios.
abstract: OBJECTIVE
  We studied the utility of occlusion distance as a function of task-relevant event density in realistic traffic scenarios with self-controlled speed.
  
  
  BACKGROUND
  The visual occlusion technique is an established method for assessing visual demands of driving. However, occlusion time is not a highly informative measure of environmental task-relevant event density in self-paced driving scenarios because it partials out the effects of changes in driving speed.
  
  
  METHODS
  Self-determined occlusion times and distances of 97 drivers with varying backgrounds were analyzed in driving scenarios simulating real Finnish suburban and highway traffic environments with self-determined vehicle speed.
  
  
  RESULTS
  Occlusion distances varied systematically with the expected environmental demands of the manipulated driving scenarios whereas the distributions of occlusion times remained more static across the scenarios. Systematic individual differences in the preferred occlusion distances were observed. More experienced drivers achieved better lane-keeping accuracy than inexperienced drivers with similar occlusion distances; however, driving experience was unexpectedly not a major factor for the preferred occlusion distances.
  
  
  CONCLUSIONS
  Occlusion distance seems to be an informative measure for assessing task-relevant event density in realistic traffic scenarios with self-controlled speed. Occlusion time measures the visual demand of driving as the task-relevant event rate in time intervals, whereas occlusion distance measures the experienced task-relevant event density in distance intervals.
  
  
  CONCLUSIONS
  The findings can be utilized in context-aware distraction mitigation systems, human-automated vehicle interaction, road speed prediction and design, as well as in the testing of visual in-vehicle tasks for inappropriate in-vehicle glancing behaviors in any dynamic traffic scenario for which appropriate individual occlusion distances can be defined.
authors.affiliation: University of Jyväskylä, Jyväskylä, Finland tuomo.kujala@jyu.fi.
authors.forename: Tuomo
authors.initials: T
authors.lastname: Kujala
authors.affiliation: University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Jakke
authors.initials: J
authors.lastname: Mäkelä
authors.affiliation: University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Ilkka
authors.initials: I
authors.lastname: Kotilainen
authors.affiliation: University of Jyväskylä, Jyväskylä, Finland.
authors.forename: Timo
authors.initials: T
authors.lastname: Tokkonen
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology*; D001334:Automobile Driving / Q000523:psychology*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008962:Models, Theoretical; D013647:Task Performance and Analysis; D055815:Young Adult
keywords: distraction; driver; driving experience; event density; event rate; expectancy; inattention; task demands; uncertainty; visual occlusion