three stories from the ltccs: using the ltccs for safety research

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

Daniel Blower

June 4, 2008

Purpose of PresentationPurpose 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 OverviewCrash 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:Story One:

Blind Zone Crashes and Truck MirrorsBlind 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

Source of drawing: Matthew Reed, UMTRI

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

Area visible using fender mirror

Area visible using planar mirror

HypothesisHypothesis

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

MethodMethod

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 InvolvementsMirror-relevant Crash InvolvementsLTCCSLTCCS

0.0 1.0 2.0 3.0 4.0

Backing

Start up, nonmotorist

Left turn, other in blindzone

Right turn, other in blind zone

Lane change/merge left

Lane change/merge right • 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 Comparison of Mirror-Relevant Crashes in LTCCS, TIFA/GESCrashes in LTCCS, TIFA/GES

0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5

Backing

Start up, nonmotorist

Left turn, other in blind zone

Right turn, other in blind zone

Lane change/merge left

Lane change/merge right

LTCCS

TIFA/GES

• Less over-representation on the right.

• Relationship in turns not observed.

• Overall proportion of involvements similar.

Left planar mirror A Pillar

Source of drawing: Matthew Reed, UMTRI

4.4

14.3

1.7

79.524.8

38.8

27.8

8.6

LCM Crashes, Position of Conflict LCM Crashes, Position of Conflict Vehicle and Blind ZonesVehicle and Blind Zones

Association of Fender/hood Mounted Association of Fender/hood Mounted Mirrors with LCM CrashMirrors with LCM Crash

Percentage with Left Fender Mirrors

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.

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

All crashes

LCM Right

0.0 10.0 20.0 30.0 40.0 50.0 60.0 70.0

All crashes

LCM left

CautionsCautions

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:Story Two:

Evaluating Technology Evaluating Technology to Reduce Rolloverto Reduce Rollover

and Loss of Control Crashesand Loss of Control Crashes

Current Project to Estimate Effectiveness of Current Project to Estimate Effectiveness of Advanced Stability TechnologiesAdvanced 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.

MethodMethod

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 Relevant Crashes in TIFA, GES, & LTCCS

Single-vehicle

14.6

30.0

16.5

0.0

5.0

10.0

15.020.0

25.0

30.0

35.0

40.0

TIFA GES LTCCS

pe

rce

nt

Rollovers

12.2

28.0

14.0

0.0

5.0

10.0

15.020.0

25.0

30.0

35.0

40.0

TIFA GES LTCCS

pe

rce

nt

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

Use of LTCCS CasesUse 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 Review of LTCCS Yaw & Roll Instability CrashesCrashes

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)

•Road curved

•Dry surface

•Cargo: loaded

3-axle tractor pulling bottom dump.

31,000 lbs cargo (dirt)

61,800 gross weight

Est. 40 mph

LTCCS Rollover Case for Simulation

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.

Researcher’s Narrative from LTCCS

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

LessonsLessons

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:Story Three:

Vehicle Mechanical Condition Vehicle Mechanical Condition and Crash Riskand Crash Risk

State-level Research Showed Vehicle State-level Research Showed Vehicle Mechanical Condition Related to Crash RoleMechanical 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 Brake Violations Increase Risk of Striking in Rear-end CrashesRear-end Crashes

FACT data FACT data

Brakeinspection results

Rear-end type

TotalTruck striking Truck struck

0 violations 15 26 41

1 or more violation 17 11 28

Total 32 37 69

proportion with violations

0 violations 46.9 70.3 59.4

1 or more violation 53.1 29.7 40.6

Total 100.0 100.0 100.0

chi=3.89, p=0.05

Lights Violations Increase Risk of Being Lights Violations Increase Risk of Being Struck in Rear-end CrashesStruck in Rear-end Crashes

FACT dataFACT data

Inspection resultsRear-end type

TotalTruck striking Truck struck

0 violations 28 23 51

1 or more violations 4 14 18

Total 32 37 69

Proportion of lighting violations

0 violations 87.5 62.2 73.9

1 or more violations 12.5 37.8 26.1

Total 100.0 100.0 100.0

chi=5.71, p=0.02

LTCCS Vehicle Inspection Data Much LTCCS Vehicle Inspection Data Much More ComprehensiveMore Comprehensive

Inspection category

LTCCS

FARS/TIFA OOS Violation

Brakes 21.7 42.1 1.9

Log 8.0 23.0 n/a

Lights 4.1 22.4 0.3

Load securement 3.4 4.6 n/a

Tires 3.3 14.3 0.9

Suspension 2.3 3.5 0.1

HOS 1.4 4.3 n/a

Steering 1.2 1.8 0.1

Frame 1.0 3.1 0.0

Wheels 0.8 3.5 incl. w/tires

Any OOS or violation 35.1 70.5 6.8

Brake Violations More Likely When Brake Violations More Likely When Truck is Striking Vehicle Truck is Striking Vehicle

in Rear-end Crashes in LTCCSin Rear-end Crashes in LTCCSBrake OOS

0.0 10.0 20.0 30.0 40.0

Rear-endstriking

Rear-endstruck

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.


Same pattern as Michigan FACT data

Brake violations

0.0 10.0 20.0 30.0 40.0 50.0 60.0

Rear-endstriking

Rear-endstruck

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


Different pattern from the Michigan FACT data

Lights OOS

0.0 5.0 10.0 15.0 20.0

Rear-endstriking

Rear-endstruck

Lights violations

0.0 10.0 20.0 30.0 40.0

Rear-endstriking

Rear-endstruck

Lessons to ApplyLessons 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.Thank you.

Questions?Questions?

three stories from the ltccs: using the ltccs for safety research

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