title: Effects of working memory load and repeated scenario exposure on emergency braking performance.
abstract: OBJECTIVE
  The objective of the present study was to examine the effect of working memory load on drivers' responses to a suddenly braking lead vehicle and whether this effect (if any) is moderated by repeated scenario exposure.
  
  
  BACKGROUND
  Several experimental studies have found delayed braking responses to lead vehicle braking events during concurrent performance of nonvisual, working memory-loading tasks, such as hands-free phone conversation. However, the common use of repeated, and hence somewhat expected, braking events may undermine the generalizability of these results to naturalistic, unexpected, emergency braking scenarios.
  
  
  METHODS
  A critical lead vehicle braking scenario was implemented in a fixed-based simulator.The effects of working memory load and repeated scenario exposure on braking performance were examined.
  
  
  RESULTS
  Brake response time was decomposed into accelerator pedal release time and accelerator-to-brake pedal movement time. Accelerator pedal release times were strongly reduced with repeated scenario exposure and were delayed by working memory load with a small but significant amount (178 ms).The two factors did not interact. There were no effects on accelerator-to-brake pedal movement time.
  
  
  CONCLUSIONS
  The results suggest that effects of working memory load on response performance obtained from repeated critical lead vehicle braking scenarios may be validly generalized to real world unexpected events.
  
  
  CONCLUSIONS
  The results have important implications for the interpretation of braking performance in experimental settings, in particular in the context of safety-related evaluation of in-vehicle information and communication technologies.
authors.affiliation: Department of Humans, Systems and Structures, Volvo Technology Corporation, Götaverksgatan 10, 405 08, Göteborg, Sweden. johan.a.engstrom@volvo.com
authors.forename: Johan
authors.initials: J
authors.lastname: Engström
authors.forename: Mikael Ljung
authors.initials: ML
authors.lastname: Aust
authors.forename: Matias
authors.initials: M
authors.lastname: Viström
mesh_terms: D000328:Adult; D001334:Automobile Driving; D005260:Female; D006801:Humans; D008297:Male; D011939:Mental Recall; D008875:Middle Aged; D011597:Psychomotor Performance; D011930:Reaction Time