title: Effects of Different Levels of Refractive Blur on Nighttime Pedestrian Visibility.
abstract: OBJECTIVE
  The aim of this study was to systematically investigate the effect of different levels of refractive blur and driver age on nighttime pedestrian recognition and determine whether clothing that has been shown to improve pedestrian conspicuity is robust to the effects of blur.
  
  
  METHODS
  Nighttime pedestrian recognition was measured for 24 visually normal participants (12 younger mean = 24.9 ± 4.5 years and 12 older adults mean = 77.6 ± 5.7 years) for three levels of binocular blur (+0.50 diopter [D], +1.00 D, +2.00 D) compared with baseline (optimal refractive correction). Pedestrians walked in place on a closed road circuit and wore one of three clothing conditions: everyday clothing, a retro-reflective vest, and retro-reflective tape positioned on the extremities in a configuration that conveyed biological motion (known as "biomotion"); the order of conditions was randomized among participants. Pedestrian recognition distances were recorded for each blur and pedestrian clothing combination while participants drove an instrumented vehicle around a closed road course.
  
  
  RESULTS
  The recognition distances for pedestrians were significantly reduced (P < 0.05) by all levels of blur compared with baseline. Pedestrians wearing biomotion clothing were recognized at significantly longer distances than for the other clothing configurations in all blur conditions. However, these effects were smaller for the older adults, who had much shorter recognition distances for all conditions tested.
  
  
  CONCLUSIONS
  In summary, even small amounts of blur had a significant detrimental effect on nighttime pedestrian recognition. Biomotion retro-reflective clothing was effective, even under moderately degraded visibility conditions, for both young and older drivers.
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Wood
authors.forename: Ralph
authors.initials: R
authors.lastname: Marszalek
authors.forename: Trent
authors.initials: T
authors.lastname: Carberry
authors.forename: Philippe
authors.initials: P
authors.lastname: Lacherez
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Collins
mesh_terms: D000063:Accidents, Traffic; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology; D001334:Automobile Driving; D003020:Clothing; D005260:Female; D005556:Form Perception / Q000502:physiology*; D006801:Humans; D008297:Male; D055254:Night Vision / Q000502:physiology*; D012030:Refractive Errors / Q000503:physiopathology*; D015348:Vision, Binocular / Q000502:physiology; D014792:Visual Acuity / Q000502:physiology*; D016138:Walking; D055815:Young Adult