CE463 Lecture 04 Human Factors

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CE463 Lecture 04Human Factors

• CE463 Highway Transportation Characteristics
• Civil Engineering
• Purdue University

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Outline

• Introduction
• Driving task
• Elements of the driving task
• Reaction time
• Perception-reaction process
• Randomness of reaction time
• Effect of task complexity
• Surprise factor
• Braking distance
• Visual acuity
• Definition
• Static visual acuity and letter size
• Other driver-related factors

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Introduction

• Driving task monitoring and responding to a
  continuous series of visual and audio cues
• Driving task at three levels
• Operational vehicle control through
  second-to-second drivers actions
• Tactical vehicle guidance through maintenance
  of a safe speed and proper path
• Strategic route planning

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Introduction

• Selected elements of operational driving
• Braking and steering
• Signs/signals reading
• Car following (road sections)
• Gap acceptance (unsignalized intersections)
• Dilemma zone (signalized intersections)

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Reaction Time

• Perception and reaction takes time
• Perception
• Stimulus reception
• Comprehension
• Decision
• Reaction
• Experiment

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Variations in Reaction Time
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Surprise Factor
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Effect of Task Complexity

• where
• tr reaction time (s)
• a minimum reaction time under circumstances (s)
• b 0.13, slope
• N no. of alternatives
• Example
• a 0.15 s and one action is possible, then
• tr 0.15 0.13 log21 0.15 0.13x0 0.15 s
• If there are two possible actions are to select
  from, then
• tr 0.15 0.13 log22 0.15 0.13x1 0.28 s

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Effect of Surprise and Task Complexity
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Braking Distance
tr 2.5 s
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Visual Acuity

• Visual acuity is 20/20 if a person can recognize
  1/3 in letter at a distance of 20 ft.
• Visual acuity is 20/x if a person can recognize
  the letters at the distance 20/x times the
  distance required by a person with visual acuity
  20/20.

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Static Acuity and Letter Size
Visual acuity is worse when an object is
moving During night conditions, the visual acuity
is one column worse
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Example
A driver with 20/20 vision can read a sign from
a distance of 90 ft. How close must a person
with the 20/50 vision be in order to read the
same sign?

• How large should letters be to be
  recognizable at a distance of 90 ft by a person
  with the 20/60 vision?

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Exercise

• Long messages require time for reading and
  comprehension.
• Dudek's Rule One second per word (four-eight
  characters), two seconds per unit of information,
  take the longer time.
• The following message is to be displayed on a
  freeway Ramp closed. Take next ramp to Main
  Street. Determine the smallest size of the
  letters that drivers can read and comprehend the
  message. What would you consider to answer this
  question?

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Other Driver Related Factors

• Age
• Fatigue
• Physical impairments
• Presence of alcohol or other drugs