CarTruck Study

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Car-Truck Study
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Published April 2002
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Purpose of Study
To examine unsafe driving actions (UDAs) that
contribute to fatal crashes between cars and
large trucks (over 10,000 lbs) and to identify
instructional strategies.
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Background

• 5,211 killed and about 140,000 injured in crashes
  involving trucks (gt10,000 lb) in 2000
• 98 of these fatalities and injuries in passenger
  cars
• 25 increase in trucks registered in last decade
• 40 increase in truck VMT in last decade

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Literature Suggests Many Car Drivers

• Are poor judges of speed, maneuverability,
  braking, acceleration of trucks
• Assume operation of car and truck is same
• Do not recognize risks associated with driving
  near trucks

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Need Better Understanding of Driver Actions
Preceding Car-Truck Crashes

• Information on UDAs is in crash data files
• Inherent uncertainty
• Police judgments, witness statements, crash
  survivors
• Straightforward tabulations and associated
  statistical techniques inadequate

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Objectives

• Examine recorded unsafe driver actions
• Identify unsafe driver actions more likely in
  car-truck crashes than in car-car crashes
• Discern behavioral patterns associated with these
  actions
• Suggest educational interventions

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Methods

• Estimate likelihood of particular UDA being
  recorded in a car-truck crash relative to a
  car-car crash.
• Examine in detail crashes with UDAs that are more
  likely in car-truck crashes.

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Vehicle Crash Data

• NASS General Estimates System GES
• All severity levels
• Complex sample
• State crash data files
• All police reported vehicle crashes in state
• Each state is different
• Fatality Analysis Reporting System FARS
• National
• All fatal vehicle crashes

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Data Selected

• FARS
• Trucks in Fatal Accident File (TIFA)
• At UMTRI
• Detailed- including police accident reports
• Limits analysis to fatal crashes

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Driver-Level Related Factors in FARS (up to 4
Per Driver Can Be Coded)

• Failure to keep in lane
• Failure to yield right of way
• Driving too fast for conditions or in excess of
  posted speed
• Inattentive
• Operating vehicle in erratic, careless or
  negligent manner
• Driving on wrong side of road
• Non traffic violation - homicide
• Sliding due to ice, water, slush

• Passing with insufficient distance
• Making improper turn
• Drowsy, sleepy, asleep, fatigued
• Overcorrecting
• Improper of erratic lane change
• Following improperly
• 94 codes

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Major Findings

• Car drivers are more likely to commit unsafe
  driving acts than truck drivers
• Unsafe driving acts for fatal car-truck crashes
  are very similar to those for fatal car-car
  crashes
• Of all 94 unsafe driver acts, 5 actions account
  for 67 of the unsafe acts by car drivers
• The same five unsafe driving acts were also the
  most common factors for truck drivers, accounting
  for 51 of unsafe acts by truckers

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Distribution of Driver Factors for Drivers in
Fatal Car-truck Crashes
Factors Per Crash
10,732 car drivers 10,732 truck drivers
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Car Drivers Are More Likely to Commit Unsafe
Driver Acts Than Truck Drivers

• Of all UDAs identified, 75 were assigned to car
  drivers and only 25 to truck drivers
• 80 of car drivers in the sample were assigned at
  least 1 UDA compared to 27 of truck drivers

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Five Most Frequent Driver Factors
100 61,466 for car-car crashes
17,867 for car-truck crashes
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UDAs Similar Between Fatal Car-Truck Crashes and
Fatal Car-Car Crashes

• This finding implies that effective programs to
  promote safe driving in general can also be used
  to promote safe driving near trucks.
• However, it must be emphasized that mistakes
  around trucks can have much more severe
  consequences.

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Five UDAs Account for Most Unsafe Acts

• Failing to keep in lane (21)
• Failing to yield right of way (16)
• Excessive speed (12)
• Failing to obey traffic control devices and laws
  (9)
• Inattention (8)

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Five Most Frequent Driver Factors Car-truck
Crashes
100 13,393 for car drivers 4,474
for truck drivers
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Same Five UDAs Also Most Common Factors for
Truck Drivers

• Failing to keep in lane (12)
• Failing to yield right-of way (14)
• Excessive speed (11)
• Failing to obey traffic control devices and laws
  (8)
• Inattention (6)

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Detailed Review of Fatal Car-truck Crash Records

• Selected sample of over 500 fatal car-truck
  crashes with one of the 4 driver factors from
  FARS 1995-1998
• Obtained crash files from TIFA records from
  center for national truck statistics
• Reviewed for behavioral sequences, driver
  characteristics, other actions/conditions

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Results From Detailed Review

• Crashes in which car driver was drowsy, asleep,
  fatigued or following improperly - male car
  drivers more likely than female
• Male and female car drivers equally likely in
  fatal crash in which they made improper lane
  change or in which their vision was obscured
• Younger car drivers- more likely to be drowsy,
  asleep, fatigued
• Older drivers - more likely to have obscured
  vision
• Younger truck drivers more likely than older to
  follow too closely

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Results From Detailed Review

• Younger car drivers - alcohol, speed
• Older car drivers - failure to yield
  right-of-way, improper turns, intersection
  problems
• Younger truck drivers more likely than older
  alcohol, speed, drugs (number of cases small)

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Conclusions

• Unsafe driver actions in fatal car-truck crashes
  attributed more to car drivers than to truck
  drivers
• Driver-factors in fatal car-truck crashes
  consistent with broader crash risks
• Most driver-related factors equally likely in
  fatal car-truck and car-car crashes
• Profile of causes and characteristics of fatal
  car-truck crashes similar to those for car-car
  crashes

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Important Limitations

• FARS data is based on police reports
• Potential survivor bias (98 of deaths are car
  occupants)
• Study is based on fatal crashes only
• Only two-vehicle crashes in sample
• Very difficult to determine causality

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The Good News
When driving near large trucks, car drivers are
largely in control of their own safety. Car
drivers who know the characteristics of large
trucks and drive accordingly are likely to be
safe.
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What Next?

• Teach drivers about trucks
• Stopping distance, blind spots, turning
  characteristics...
• Teach car drivers about 5 unsafe actions
• Failing to keep in lane
• Failing to yield right-of way
• Excessive speed
• Failing to obey traffic control devices and laws
• Inattentive

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What Next?

• Emphasize share-the-road strategies
• Await results of DOTs Truck Causation study

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The AAA Foundation for Traffic Safety is a
501(c)(3) public charity located in Washington,
DC that is dedicated to research and education
about the causes of traffic crashes. It is
supported by by donations from AAA/CAA Clubs,
AAA/CAA members, and other organizations
associated with the American Automobile
Association/Canadian Automobile Association.