Car-Truck Study
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Purpose of Study - PowerPoint PPT Presentation

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Car-Truck Study. Published April 2002. 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. Background.

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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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  • 5,211 killed and about 140,000 injured in crashes involving trucks (>10,000 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 Car-Truck Crashes

  • 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 Car-Truck Crashes

  • 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 Car-Truck Crashes

  • 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 Car-Truck Crashes

  • FARS

  • Trucks in Fatal Accident File (TIFA)

    • At UMTRI

    • Detailed- including police accident reports

  • Limits analysis to fatal crashes

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Failure to keep in lane Car-Truck Crashes

Failure to yield right of way

Driving too fast for conditions or in excess of posted speed


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


Improper of erratic lane change

Following improperly

94 codes

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

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Major Findings Car-Truck Crashes

  • 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



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 Than Truck Drivers

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 Car-Car CrashesUnsafe 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-Car CrashesCar-truck Crashes

100% = 13,393 for car drivers

= 4,474 for truck drivers

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Same Five UDAs Also Most Common Car-Car CrashesFactors 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-Car CrashesCar-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 Car-Car Crashes

  • 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 Car-Car Crashes

  • 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 Car-Car Crashes

  • 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 Car-Car Crashes

  • 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 Car-Car Crashes

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? Car-Car Crashes

  • 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? Car-Car Crashes

  • Emphasize share-the-road strategies

  • Await results of DOT’s 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.