Pedestrians with Vision Loss or Blindness

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Pedestrians with Vision Loss or Blindness
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How many people are blind or visually impaired now

• 4.3 million Americans are severely visually
  impaired
• 1.1 million are legally blind
• Incidence increases with age
• By 2010, expect there to be 20 million visually
  impaired persons over age 45

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Variations in Vision Loss
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How do pedestrians who are blind or visually
impaired travel?
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Pedestrians who are blind or visually impaired in
the US do travel to new locations or
intersections and figure them out by listening
and exploring

• Transportation choices
• Walk
• Bus or rail transit
• Taxis, friends, relatives, or paid drivers

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Obstacle detection and curb detection techniques

• Long white cane used as a probe of the walking
  surface
• Dog guide to used guide around obstacles or stop
  at curbs or dropoffs
• Low vision travelers may use their vision and an
  aid such as a telescope

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Orientation and alignment cues

• Detect slight slopes under foot and/or a
  detectable change in surface texture
• Listen to direction that cars are traveling to
  align to cross
• Listen to when the cars start moving in the
  closest lane as indication of time to cross
• Maintain awareness of buildings, sun, other
  pedestrians, smells, and sounds which provide
  information
• Ask a lot of questions

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Crossing at a signalized intersection
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Problem areas for travelers who are blind

• Locating the crosswalk
• Detecting a gap in traffic

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Locating the crosswalk

• Preventing crossing into the circulatory roadway
• Finding the crosswalk
• Aligning to cross

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Australia
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Detecting a gap in traffic

• Hearing is not as specific as vision
• With vision, can select just one lane or area to
  check not possible when crossing using audible
  cues only
• Pedestrians with low vision may have more
  difficulty with depth perception and judging speed

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Masking by other cars

• Cars that have just passed the crosswalk
• Cars in the circulatory roadway
• Car approaching in other lane of street the
  pedestrian is crossing
• Car that stops to allow the pedestrian to cross
  (multi-lane roundabout)

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Sighted pedestrian crossing
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Blind pedestrian crossing
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Ongoing Research

• National Eye Institute of the National Institutes
  of Health has funded a five year project on Blind
  Pedestrians Access to Intersections
• Roundabouts blind and low vision individuals
• Accessible Pedestrian Signals
• Detectable warnings
• June 2000 May 2005

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NEI-Supported Study of Roundabouts Access

• To date
• Evaluated gap judgments by sighted and blind
  individuals at 5 roundabouts with volumes from
  12,000 to 35,000 estimated AADT
• 2 Single lane and 3 multi-lane

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NEI study - Traffic Volume

• Higher volumes yielded fewer crossable gaps
• Higher volumes resulted in more unsafe judgments,
  more missed gaps, and longer periods of time
  between the beginning of a crossable gap and the
  point at which a blind person detected it

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NEI study - Unsafe judgments

• Blind participants were more than twice as likely
  to make unsafe judgments as sighted participants
• Time of day differences
• Little difference between judgments of blind and
  sighted individuals at mid-day
• Substantial differences at rush hour

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NEI study Latency and delay

• Blind pedestrians detected gaps later than
  sighted pedestrians
• Baltimore 3 seconds later
• Tampa 5.5 seconds later
• Blind pedestrians require longer gaps in order to
  detect the gap and cross

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Experience in other countries

• Reports from pedestrians who are blind or
  visually impaired indicate that roundabouts are
  often considered a barrier to independent travel

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Australia

• Individuals who are blind or visually impaired
  and Orientation and Mobility Specialists state
  that blind pedestrians
• Avoid crossing at roundabouts
• Often severely limit where they can travel
• Roundabouts there may have detectable warnings
  and tactile guidestrips

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England

• Pedestrians who are blind or visually impaired
  state that roundabouts can be very difficult to
  cross
• Signals are installed at some roundabout
  locations, as are raised crosswalks

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Review - Problem areas

• Difficulty finding appropriate location to begin
  crossing
• Latency and delay in detecting gap, and
  subsequent inability to cross
• Unsafe judgments about gaps