title: Even moderate visual impairments degrade drivers' ability to see pedestrians at night.
abstract: OBJECTIVE
  To determine the effect of moderate levels of refractive blur and simulated cataracts on nighttime pedestrian conspicuity in the presence and absence of headlamp glare.
  
  
  METHODS
  The ability to recognize pedestrians at night was measured in 28 young adults (M = 27.6 years) under three visual conditions: normal vision, refractive blur, and simulated cataracts; mean acuity was 20/40 or better in all conditions. Pedestrian recognition distances were recorded while participants drove an instrumented vehicle along a closed road course at night. Pedestrians wore one of three clothing conditions and oncoming headlamps were present for 16 participants and absent for 12 participants.
  
  
  RESULTS
  Simulated visual impairment and glare significantly reduced the frequency with which drivers recognized pedestrians and the distance at which the drivers first recognized them. Simulated cataracts were significantly more disruptive than blur even though photopic visual acuity levels were matched. With normal vision, drivers responded to pedestrians at 3.6- and 5.5-fold longer distances on average than for the blur or cataract conditions, respectively. Even in the presence of visual impairment and glare, pedestrians were recognized more often and at longer distances when they wore a "biological motion" reflective clothing configuration than when they wore a reflective vest or black clothing.
  
  
  CONCLUSIONS
  Drivers' ability to recognize pedestrians at night is degraded by common visual impairments, even when the drivers' mean visual acuity meets licensing requirements. To maximize drivers' ability to see pedestrians, drivers should wear their optimum optical correction, and cataract surgery should be performed early enough to avoid potentially dangerous reductions in visual performance.
authors.affiliation: School of Optometry and Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia.
authors.forename: Joanne M
authors.initials: JM
authors.lastname: Wood
authors.forename: Richard A
authors.initials: RA
authors.lastname: Tyrrell
authors.forename: Alex
authors.initials: A
authors.lastname: Chaparro
authors.forename: Ralph P
authors.initials: RP
authors.lastname: Marszalek
authors.forename: Trent P
authors.initials: TP
authors.lastname: Carberry
authors.forename: Byoung Sun
authors.initials: BS
authors.lastname: Chu
mesh_terms: D000328:Adult; D001334:Automobile Driving; D002386:Cataract / Q000503:physiopathology*; D003198:Computer Simulation; D015350:Contrast Sensitivity / Q000502:physiology; D003624:Darkness; D005260:Female; D005556:Form Perception / Q000502:physiology*; D019466:Glare; D006801:Humans; D008297:Male; D012030:Refractive Errors / Q000503:physiopathology*; D015354:Vision, Low / Q000503:physiopathology*; D014792:Visual Acuity / Q000502:physiology; D019987:Persons with Visual Disabilities; D055815:Young Adult