Why do Cell Phone Conversations Interfere with Driving?

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Why do Cell Phone Conversations Interfere with
Driving?

• David Strayer, Frank Drews, Bill Johnston
• Department of Psychology
• University of Utah

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Do Cell Phones Interfere With Driving?
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Driver Inattention Cell Phones

• Currently 130 million cell phone subscribers in
  US
• 60 of cell phone time is spent while driving
• Tens of millions of people driving while using
  the cell phone each day
• Anecdotal evidence suggests that cell phones
  interfere driving

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Research Questions

• Does conversing on a cell phone interfere with
  driving?
• How significant is the interference?
• What are the causes the interference?-
  Peripheral interference (dialing, holding the
  phone)- Attentional interference (cell phone
  conversation)
• Legislative initiatives tacitly endorse the
  peripheral interference hypothesis

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Study I

• Conditions- Hand-Held Cell Phone- Hands-Free
  Cell Phone- Radio Control- Book on Tape Control

• Conversations- Clinton Impeachment- Olympic
  Bribery Scandal

Driving Conversation
Driving
Driving
Warm-up
36 minutes
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Response to Simulated Traffic Signals

• Subjects responded to red and green traffic
  signals
• Measures- Probability of missing signals-
  Reaction time to detected signals
• Preliminary Analysis- Hand-Held Hands-Free -
  Radio Control Book on Tape Control

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Single
Dual
Cell Phone
Control
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Study I
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Study I
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Conclusions (Study I)

• Using a cellular phone while driving impairs
  performance - Twice as likely to miss
  critical/unpredictable events - Slower to react
  to critical/unpredictable events
• Cell phone conversation itself causes the
  interference
• Hands-free phones do not appear to be the
  solution, because the deficits appear to be due
  to attentional demands imposed by the conversation

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High-Fidelity Simulator Study
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Study II

• Conditions- Traffic Density (Low vs.
  High)- Task (Single vs. Dual)

• Procedure- Four 10-mile multilane freeway
  segments- Follow a pace car that brakes
  periodically

Adaptation
D3
D2
D1
C1
D4
80 minutes
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Cell Phone Conversations

• Conversations with confederate- Topics
  determined in pre-experimental questionnaire
• Hands-free cell phones, call initiated before
  driving
• Any interference must be due to the cell phone
  conversation, because there is no manual
  manipulation of the cell phone

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Response to Braking Pace Car

• Performance Measures- Time to initiate
  braking- Time to take foot off brake pedal-
  Driving speed- Following distance- Number of
  accidents

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Single
Dual
Low Density
High Density
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Brake Profile
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Study II
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Study II
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Speed Profile
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Study II
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Following Distance Profile
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Study II
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Conclusions(Study II)

• Drivers using cell phones exhibit sluggish
  behavior- Slower to initiate braking - Depress
  brake longer - Take longer to reach their
  minimum speed
• Drivers using a cell phone try to compensate
  by- Driving slower- Increasing their following
  distance- But inadequate (more accidents in
  dual-task, high density)
• Using hands-free wireless communication
  interferes with driving by diverting attention to
  an engaging cognitive context not immediately
  associated with driving

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Future Directions

• How do other advanced technologies affect driving
  performance?

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Conclusions
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Future Directions

• How does this compare with conversations with
  passengers in the car?
• How does the nature of the conversation modulate
  the effect?
• How does this compare with driving under the
  influence of alcohol?
• How does expertise affect these divided attention
  deficits?
• Are these deficits exacerbated with age?
• How great are the individual differences in
  distraction?

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Braking Profile
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Braking Profile
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Following Distance Profile
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Speed Profile
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Brake Profile