Three stories from the ltccs using the ltccs for safety research
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Three Stories from the LTCCS: Using the LTCCS for Safety Research. Daniel Blower June 4, 2008. Purpose of Presentation. Illustrate the strengths and limitations of the LTCCS using experience from three research projects: Truck mirrors and blind zones.

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Three Stories from the LTCCS: Using the LTCCS for Safety Research

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Three Stories from the LTCCS:Using the LTCCS for Safety Research

Daniel Blower

June 4, 2008

Purpose of Presentation

  • Illustrate the strengths and limitations of the LTCCS using experience from three research projects:

    • Truck mirrors and blind zones.

    • Evaluating effectiveness of advanced stability technologies.

    • Effect of truck mechanical condition on truck crashes.

Crash Data Overview

  • Trucks Involved in Fatal Accidents (TIFA)

    • Fatal crashes only; census file; survey to supplement FARS; since 1980.

  • General Estimates System (GES)

    • All police-reported crashes; sample file; nationally representative; since 1987.

  • Large Truck Crash Causation Study (LTCCS)

    • Fatal, A-, B-injury crashes; sample file; nationally-representative; 2001-2003

Story One:Blind Zone Crashes and Truck Mirrors

  • National crash data show that mirror-relevant crashes overinvolved on the right.

    • No detail on truck mirror configuration in any available crash data.

  • Large Truck Crash Causation Study data offers more detailed information.

    • Presence of side & fender mirrors.

    • Available materials such as scene diagram, photos, extensive narrative, interviews with all parties to code additional data.

Mirror and Direct Fields of View for One Truck & Driver

Blocked by left planar mirror

Blocked by A Pillar

Area visible using fender mirror

Note car fits neatly in area visible only using fender-mirror

Area visible using planar mirror

Source of drawing: Matthew Reed, UMTRI


  • Fender-mounted mirrors reduce the over-representation of right-side blind zone crashes.


  • Reproduce classification algorithm in LTCCS data.

  • Review scene diagrams/narrative to verify blind zones.

  • Code position of conflict vehicles.

    ► Are the vehicles in the blind zones?

  • Compare crash configuration with mirror configuration.

    ► Do right fender-mounted mirrors help?

Mirror-relevant Crash InvolvementsLTCCS

  • Mirror-relevant are 7.2% of all.

  • LCM Right 1.9 times LCM Left

  • Right turn 0.7 times left turn

  • Backing ~0.3%

Mirror-relevant Crash InvolvementsLTCCS

  • Mirror-relevant are 7.2% of all.

  • LCM Right 1.9 times LCM Left

  • Right turn 0.7 times left turn

  • Backing ~0.3%

Comparison of Mirror-Relevant Crashes in LTCCS, TIFA/GES

  • Less over-representation on the right.

  • Relationship in turns not observed.

  • Overall proportion of involvements similar.

LCM Crashes, Position of Conflict Vehicle and Blind Zones

Left planar mirror

A Pillar




Source of drawing: Matthew Reed, UMTRI


Association of Fender/hood Mounted Mirrors with LCM Crash

Percentage with Right Fender Mirrors

  • Trucks in LCM Right crashes somewhat more likely to have right fender mirrors.

  • Trucks in LCM Left crashes somewhat less likely to have left fender mounted mirrors.

  • Neither difference is statistically significant.

  • 29 unweighted LCM right cases.

  • 23 unweighted LCM left cases.

Percentage with Left Fender Mirrors


  • Small sample sizes limit conclusions: the size of the effects are not statistically significant.

  • LTCCS not well-suited for analysis of infrequent events.

  • Use of researcher’s summary, diagrams, photographs is labor intensive but worth the effort.

Story Two:Evaluating Technology to Reduce Rolloverand Loss of Control Crashes

Current Project to Estimate Effectiveness of Advanced Stability Technologies

  • Roll stability control & electronic stability control technologies available for trucks.

  • Goal is to reduce rollover & loss of control crashes.

  • Current project to estimate effectiveness in real-world crashes.


  • Identify scope of crashes where the technology is relevant.

  • Identify vehicle & environmental factors that contribute to the crashes.

  • Engineering evaluation of real-world crashes to estimate effect.

  • Hardware-in-the-loop simulation of technologies in real-world crashes.

Relevant Crashes in TIFA, GES, & LTCCS

(K) (K, A, B) (K, A, B)

(K) (K, A, B) (K, A, B)

Use of LTCCS Cases

  • Specific limitations:

    • Relatively few cases: 963 crashes, 1123 vehicles.

    • Questions about national representativeness. (E.g., about twice as many rollovers as expected)

  • Therefore, in light of the limitations:

    • Use TIFA/GES to determine national distribution of yaw & roll instability crash scenarios

    • Apply algorithm to classify yaw and roll cases developed in TIFA/GES to LTCCS to establish crash types

    • Exploit superior detail of LTCCS to produce exemplars of the crash types for engineering review and simulation

Review of LTCCS Yaw & Roll Instability Crashes

  • Review of:

    • 83 yaw instability cases

    • 81 roll instability cases

  • Assess for

    • Accuracy of coding

    • Suitability for Hardware in the Loop simulation

    • Crash details (radius of curvature, curve entry speed)

    • Relevance of roll & yaw control technologies (likely, probably, unlikely, unknown)

LTCCS Rollover Case for Simulation

  • Road curved

  • Dry surface

  • Cargo: loaded

  • 3-axle tractor pulling bottom dump.

  • 31,000 lbs cargo (dirt)

  • 61,800 gross weight

  • Est. 40 mph

Researcher’s Narrative from LTCCS

A single vehicle crash occurred on the southbound on-ramp for a four-lane northbound divided state highway in the early afternoon hours. This transition ramp comes off of a two-lane state highway. The ramp is one-lane with a -4/122cm (-3%) grade and a super-elevation of approximately 8/122cm (+7%). Narrow paved shoulders bordered each side of the on-ramp. Paved shoulders bordered the highway as well. The posted speed limit for the northbound highway was 65 mph (105 kmph).The on-ramp speed limit is unknown. There are no curve warning signs posted from the overpass all the way through the ramp curve. This is inadequate roadway signage for the curvature and ramp speed, and considered an associative factor for this crash. There was no traffic congestion, adverse weather conditions or sight restrictions at the time of the crash. Vehicle one, a 1995 Freightliner FLD-120 tractor pulling a 1999 Red River bottom-dump trailer, loaded with dirt was southbound on the on-ramp as it entered the curve. According to the police report, the truck was traveling at about 40 mph (64 kmph) as it drove down the ramp. As the truck approached the end of the curve, the truck began to skid in a clockwise direction, leaving 77 feet (23 meters) of scuffmarks. The trailer rolled to its left, pulling the tractor with and both units fell onto their left sides in the first lane of the eastbound highway. The units slid in an eastbound direction for another 64 feet (20 meters) before coming to rest in the first and second lanes, facing eastbound. The load of dirt was spilled into the second lane. … At the time of the crash the Freightliner was hauling 31,140 lbs (14,125 kgs) of dirt. The entire unit weighed 61,879 lbs (28,067 kgs). … This driver drives this vehicle daily and over this route daily. This driver stated that he down shifted into fourth as he was negotiating the curve when he noticed that the trailer started to rollover. The driver did not realize that he was traveling to fast for the curve with the load that he was carrying.

Engineering assessment: Roll control likely relevant; Yaw control unlikely relevant


  • Very rich crash investigations, scene & vehicle documentation support engineering analysis.

  • Both uniform and of high quality.

  • Reasons to question some national estimates from LTCCS.

  • No current alternative for rich detail available from LTCCS.

Story Three:Vehicle Mechanical Condition and Crash Risk

State-level Research Showed Vehicle Mechanical Condition Related to Crash Role

  • FACT data from Michigan, 1996-2001

  • CVSA Level 1 inspection & detailed crash events

  • Rear-end crashes:

    • Higher rates of brake violations when the truck is the striking vehicle.

    • Higher rates of light violations when truck is the struck vehicle

  • FACT program a forerunner of LTCCS

Brake Violations Increase Risk of Striking in Rear-end CrashesFACT data

Lights Violations Increase Risk of Being Struck in Rear-end CrashesFACT data

LTCCS Vehicle Inspection Data Much More Comprehensive

Brake Violations More Likely When Truck is Striking Vehicle in Rear-end Crashes in LTCCS

  • In rear-end crashes, trucks that are the striking vehicle have higher rates of brake violations and out-of-service than as the struck vehicle.

  • Neither difference is statistically significant.

  • Same pattern as Michigan FACT data

Mixed Results for Light System Violations in Rear-end Crashes, LTCCS

  • In rear-end crashes, trucks that are the struck vehicle have higher rates of light system OOS.

  • Rates the same for all lights violations.

  • Neither difference is statistically significant.

  • Different pattern from the Michigan FACT data

Lessons to Apply

  • LTCCS invaluable as source of detailed crash data.

    • Engineering reviews of crash narratives, etc.

    • Availability of critical information such as mirror configuration and mechanical condition.

  • Restricted sample sizes pose problems

  • Care must be used in choosing truck safety issues and methods to address.

  • Representativeness can be an issue.

Thank you.Questions?

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