For the full report and more information please visit: http://matc.unl.edu/research/research_projects.php?researchID=6 In order to improve the safety of the overall surface transportation system each of the critical areas needs to be addressed separately with more focused attention. Statistics clearly show that large truck crashes contribute significantly to an increased percentage of high severity crashes. It is therefore important for the highway safety community to identify the characteristics and contributory causes related to large truck involved crashes. During the first phase of this study fatal crash data from Fatality Analysis Reporting System database are studied to achieve that objective. In this second phase, it is proposed to analyze truck crashes of all severity levels with the intention of identifying the factors contributing to increased severities of truck crashes, which could not be achieved by analyzing fatal crashes alone. Dr. Sunanda Dissanayake, Professor at Kansas State University, presented this research during the 2012 MATC Spring Webinar Series.

1. Characteristics and Contributory
Causes Related to Large Truck
Crashes
Sunanda Dissanayake, Ph.D., P.E.
Associate Professor
Kansas State University

2. Disclaimer
• The Contents of this report reflect the view of
the authors, who are responsible for the facts
and the accuracy of the information presented
herein. This document is disseminated under
the sponsorship of the Department of
Transportation University Transportation
Center Program, in the interest of information
exchange. The U.S. Government assumes no
liability for the contents or use thereof.

3. Outline
• Introduction
• Objectives
• Methodology
• Data
• Results
• Conclusions

4. Introduction
• One ninth of all traffic fatalities in US involved
a large truck.
• However, large trucks accounted for only 3%
of registered vehicles and 7% of vehicle miles
traveled.
• Truck crashes tend to be more severe than
other crashes.
• Important to identify characteristics and what
leads to increased severities.

5. Trucks?
For the purpose of this study:
Large trucks: Trucks with gross weight of
10,000 pounds or more.

6. Objectives
• To identify characteristics and contributory
causes related to fatal truck crashes and all
truck crashes.
• To compare circumstances more common in
fatal truck crashes as compared to fatal non-
truck crashes.
• To identify the factors that are contributing
to/related with increased severity of truck
crashes.

7. Methodology and Data
• Objectives achieved by analyzing crash data
related to large trucks.
•Two phases of the study:
–One focused on fatal truck crashes from the
whole country
–Second focused on all truck crashes from
Kansas
•Statistical Modeling techniques used.

8. Analysis of Fatal Truck
Crashes
• FARS database.
• Includes all police-reported fatal crash data
from the whole country.
• Very detailed data with many coded variables.
• Fatality occurred within 30 days of the
incident.

9. Question………
• How many fatal truck crashes in the
United States each Year?

11. Analysis of Fatal Truck Crashes
Vehicle Occupants killed in Large Truck Crashes
6000
5000
4000 No. of fatalities
No. of Fatalities
in trucks
No. of fatalities
3000
in Non-trucks
Total
2000
1000
0
1998 1999 2000 2001 2002 2003 2004 2005 2006 2007
Year
Particularly devastating to the occupants of the
other vehicle.

12. Source: DRIVECAM Website
• Sad fact: Majority of the damage is to the
occupants of the other vehicle.

13. Analysis of Fatal Truck Crashes
Based on manner of collision – fewer
single vehicle truck crashes

14. Analysis of Fatal Truck Crashes –
Bayesian method – crash related
Ex. Construction/work area  LR = 2.77
Fatal truck crashes are 2.77 more likely in
construction/work areas

15. Analysis of Fatal Truck Crashes –
Bayesian method –vehicle related
Ex. Defective Brake Systems  LR = 8.22
Fatal truck crashes are 8.22 times more
likely to have defective brake systems

16. Analysis of Fatal Truck Crashes –
Bayesian method-driver related
Ex. Following Improperly  LR = 3.7
Fatal truck crashes are 3.7 more likely to
have a driver that was following improperly.

17. Phase II – All Crashes
• Data from Kansas
• KDOT’s Kansas Accident Reporting System
database
• Data related to truck crashes occurred
between 2004 and 2008 considered.
• 18,919 observations.
• Characteristics and Contributory causes
identified; severity modeling carried out.

18. BINARY LOGISTIC REGRESSION
• Variables were redefined in binary form; 1 or 0.
• Variables checked for multicollinearity.
• Binary Logistic Regression model developed
• Dependent Variable crash severity was redefined
as:
= 1, if the occupants involved in the truck crash
sustained injury of any severity level; = 0, otherwise
• Sign of the variable important, Odds Ratio used to
quantify the level of importance

19. RESULTS AND DISCUSSION
CHARACTERISTICS OF TRUCK CRASHES
Road Surface Type
Dirt
(1.1%) Brick
Gravel (0.5%)
(3.1%)
Concrete
(30.6%)
Blacktop
(64.4%)
More truck crashes on Blacktop –makes
sense !

20. Road Surface Condition Road Surface Character
Ice, Snow Mud, Dirt Curved and
packed or Sand Level Curved on
(6.2%) (0.5%) (5.5%) Grade
(5.3%)
Snow and
Slush Straight at
(3.5%) hillcrest
(1.7%)
Wet
(10.3%) Straight on
Grade
(19.3%) Straight
and level
Dry (67.3%)
(79.2%)
More Truck Crashes More Truck Crashes
under Dry road on straight and level
surface condition

21. Lane Class
Eight Lane Two Lane
Divided Divided (0.2%)
(2.3%)
Four Lane
Undivided
(9.3%) Two Lane
Undivided
(38.8%)
Six Lane
Divided
(14.1%)
Four Lane
Divided
(35.3%)
2-lane undivided very
critical

22. Light Condition
80.0% 76.0%
70.0%
Percentage of Truck Crashes
60.0%
50.0%
40.0%
30.0%
20.0%
12.5%
7.6%
10.0%
2.3% 1.5%
0.0%
Daylight Dawn Dusk Dark-Street Lights Dark-No Street
on Lights
Light Condition
Majority under daylight conditions –
exposure ?

23. Weather Condition Time of Day
Strong Freezing Snow and 25.0% 22.5%
21.0%
Percentage of Crashes
Winds Rain Winds
18.8%
(1.7%) (1.0%) (1.4%) 20.0%
15.3%
Snow 15.0%
(4.4%) 8.8%
10.0%
5.2%
5.0% 3.6% 4.8%
Rain, Mist
or Drizzle 0.0%
(6.9%)
No Adverse
Condition
(81.8%)
Time of the Day
82% -Under no 78% - 6 am to 6 pm
adverse weather

24. Age of the Truck Driver Gender of the Driver
60.0% 90.0%
78.7%
Percentage of Total Truck Crashes
48.9% 80.0%
50.0%
70.0%
Percentage of Crashes
40.0% 60.0%
31.5%
50.0%
30.0%
40.0%
20.0% 30.0%
20.0% 16.9%
9.3%
10.0% 5.7%
4.3% 10.0% 4.4%
0.1%
0.0% 0.0%
16-20 21-40 41-60 61-80 >80 Others Male Female Unknown
Age of the Truck Driver (Years) Gender of the Truck Driver
Majority – middle aged Majority - male

25. Truck Maneuver
60.0%
54.6%
50.0%
Percentage of Crashes
40.0%
30.0%
19.1%
20.0%
10.0% 8.0% 7.7%
5.3% 5.3%
0.0%
Straight-following Right turn Left turn Backing Changing lanes Others
road
Truck Maneuver
Distribution of Truck Crashes based
on Truck Maneuver

26. Manner of Collision
40.0%
35.2%
35.0%
30.0%
Percentage of Crashes
25.0%
19.7%
20.0%
16.5%
15.3%
15.0%
10.0%
4.1% 3.3%
5.0%
1.4% 1.8%
0.0%
Single Angle-Side Rear End Sideswipe Backed into Sideswipe Head On Unknown
Vehicle Impact (Same (Opposite
Direction) Direction)
Manner of Collision
More single vehicle crashes than in
fatal truck crashes

27. Vehicle Body Type Accident Class
Other non-
Sport Utility Others collision Other
Collision with Collisions
Vehicle (1.6%) parked motor
(3.6%)
(12.5%) (1.4%)
vehicle
(3.8%)
Collision with
Pickup animal
Truck (7.1%)
(20.4%)
Overturned
(7.6%) Collision with
other motor
Collision with vehicle
Van Automobile fixed object (63.2%)
(8.6%) (56.0%) (13.3%)
Distribution of Two- Distribution of Truck
Vehicle Truck Crashes Crashes based on
Based on Body Type Accident Class

28. Road Function Class
30.0%
25.1%
25.0%
Percentage of Crashes 21.9%
20.0%
15.8%
14.9%
15.0% 13.1%
10.0%
5.8%
5.0% 2.7%
0.6%
0.0%
Road Function Class
More in rural areas

29. Accident Location
60.0%
49.4%
Percentage of Crashes
50.0%
40.0%
30.0%
20.0% 16.6%
12.4%
8.0% 6.9% 5.6%
10.0%
0.9%
0.0%
Accident Location
50% - at non-
intersection locations

30. Average Annual Daily Traffic
70.00% 63.74%
60.00%
Percentage of Crashes
50.00%
40.00%
30.00%
20.00% 14.29%
10.00% 6.98% 4.95%
2.84% 3.33% 2.97% 0.90%
0.00%
Average Annual Daily Traffic (AADT)
Distribution of Truck Crashes based
on Average Annual Daily Traffic

31. Contributory Causes of Truck
Crashes
Question:
• What is the most common type of contributory
cause?
Driver related?
Roadway?
Environment related?
Vehicle defects?
Other?

32. Contributory Causes of Truck
Crashes
Truck Crashes Based on Type of Contributory Cause
Type of % of Crashes
Number of
Contributory Involving
Truck Crashes
Cause Contributory Cause
Driver Related 13,260 73%
Environment
2,360
Related 13%
Road Related 1,409 7.8%
Vehicle Related 1,112 6.1%
Pedestrian
30
Related 1.7%

33. Truck Crashes Based on Driver
Contributory Cause
Number of Percentage of Crashes Involving
Driver Related Contributory Cause
Crashes Driver Related Cause
Failed to give time and
6,458 35.50%
attention
Too fast for conditions 1,962 10.80%
Failed to yield right of way 1,644 9.00%
Improper lane change 1,196 6.60%
Followed too closely 1,178 6.50%
Made improper turn 1,016 5.60%
Disregard traffic signs, signal 770 4.20%
Avoidance or evasive action 742 4.10%
Improper backing 726 4.00%
Improper passing 487 2.70%
Wrong side or wrong way 337 1.90%
Distraction in or on the truck 327 1.80%
Fell asleep 307 1.70%
Under influence of alcohol 250 1.40%
Reckless/careless driving 197 1.10%
Ill or medical condition 105 0.60%
Exceeded posted speed limit 101 0.60%
Did not comply with license restriction 91 0.50%
Improper or no signal 77 0.40%
Impeding traffic, too slow 76 0.40%
Under influence of drugs 66 0.40%
Aggressive, antagonistic driving 46 0.30%
Improper parking 46 0.30%

34. Truck Crashes Based on
Vehicle Contributory Causes
Number of Percentage of Crashes
Vehicle Related Contributory Cause
Crashes Involving Vehicle
Related Cause
Falling Cargo 389 34.0%
Defective Tires 220 19.2%
Defective Brake System 175 15.3%
Defective Wheel(s) 128 11.2%
Trailer-coupling related 85 7.4%
Other lights 48 4.2%
Unattended or driverless (not in motion) 41 3.6%
Unattended or driverless (in motion) 22 1.9%
Defective Windows-windshield 18 1.6%
Defective Exhaust System 12 1.0%
Headlights 5 0.4%

35. Truck Crashes Based on
Environment-Related Contributory
Causes
Number of
Environment Related Contributory Cause Percentage of Crashes
Crashes
Involving Environment
Related Cause
Animal Related 966 37.8%
Rain, mist or drizzle 388 15.2%
Falling snow 352 13.8%
Strong winds 336 13.2%
Sleet, hail, freezing rain 185 7.2%
Vision obstruction - glare 93 3.6%
Vision obstruction - cultural 77 3.0%
Fog, smoke or smog 75 2.9%
Blowing sand, soil, dirt 39 1.5%
Vision obstruction - vegetation 26 1.0%
Reduced visibility due to cloud cover 17 0.7%

36. Truck Crashes Based on Road-
related Contributory Causes
Photo credit: Iowa State University

37. Truck Crashes Based on Road-
related Contributory Cause
Number of Percentage of Crashes
Road Related Contributory Cause
Crashes Involving Road Related
Cause
Icy or Slushy 686 45.7%
Wet 281 18.7%
Snow-packed 239 15.9%
Debris or Obstruction 113 7.5%
Road Under Construction/Maintenance 79 5.3%
Shoulders 69 4.6%
Ruts, Holes, Bumps 20 1.3%
Inoperative Traffic Control Device 14 0.9%

38. Binary Logistic Regression
Example of Variables Considered in the Model
Variable Mean Standard Deviation Description
=1 if the truck driver is under the influence of alcohol,
ALCOHOL 0.01586 0.1249
=0 otherwise
BRAKES 0.03547 0.18496 =1 if the crash occurred due to brakes, exhaust, headlights, windows-windshield, cargo or
tires, =0 otherwise
CARELESS 0.01813 0.13342 =1 if the truck driver is distracted or is too aggressive, =0 otherwise
CC_DR 0.69898 0.45871 =1 if the crash occurred has driver related contributory cause,
CC_ENV 0.12464 0.33032 =1 if the crash occurred has environment related contributory cause,
CC_RD 0.07448 0.26255 =1 if the crash occurred has road related contributory cause,
CC_VEH 0.0583 0.23432 =1 if the crash occurred has truck related contributory cause,
CLASS 0.63169 0.48236 =1 if the crash involves collision with a motor vehicle in transport,
=0 otherwise
COLLISION 0.17929 0.38361 =1 if the crash involved a head-on collision, =0 otherwise
CONSTR_MAINT 0.05872 0.23511 =1 if crash occurred in construction, maintenance or utility zone,
CONTROL 0.81077 0.3917 =1 if the crash site has a traffic control device, =0 otherwise
DAMAGE 0.86432 0.34246 =1 if the truck had a damage, =0 otherwise
DAY 0.87774 0.32759 =1 if crash occurred during weekdays, =0 otherwise
DRUGS_ALCOHOL 0.01617 0.12615 =1 if the truck driver is influenced with drugs or alcohol, =0 otherwise
TRAPPED 0.0195 0.13829 =1 if truck driver was trapped, =0 otherwise
EVASIVE 0.0481 0.21398 =1 if the truck driver took evasive action or is too slow, =0 otherwise
GENDR 0.78699 0.40945 =1 if the driver of the truck was a male, =0 otherwise
IMP_MAN 0.1313 0.33773 =1 if the truck driver made improper maneuver, =0 otherwise
INOPERATIVE 0.00476 0.06881 =1 if the crash occurred at construction site or has inoperative traffic control device, =0
otherwise
LIGHT 0.75961 0.42733 =1 if the light condition is daylight, =0 otherwise

39. Parameter Estimates and Odds Ratio of Large truck
Crashes in the Model 95% Wald
Estimat Standard Odds Confidence
Variable e Error
Pr > Chi-Sq
Ratio Limits For Odds
Ratio
Intercept* -1.522 0.163 <0.0001
ALCOHOL 2.04,3.4
0.979 0.135 <0.0001 2.66
* 7
CARELESS* 0.334 0.126 0.0078 1.40 1.09, 1.79
CC_DR* 0.6 0.054 <0.0001 1.82 1.64, 2.02
CC_RD* -0.332 0.084 <0.0001 0.72 0.61, 0.85
CC_VEH -0.09 0.093 0.3329 0.91 0.76, 1.10
CLASS 0.102 0.052 0.0509 1.11 1.00, 1.23
COLLISION* 0.471 0.052 <0.0001 1.60 1.45, 1.77
CONSTR_MAINT* -0.267 0.083 0.0013 0.77 0.65, 0.90
Examples CONTROL*
DAMAGE*
DAY
0.308
1.116
-0.003
0.057
0.083
0.058
<0.0001
<0.0001
0.9661
1.36
3.05
1.00
1.22, 1.52
2.60, 3.59
0.89, 1.12
EVASIVE* 0.427 0.079 <0.0001 1.53 1.31, 1.79
GENDR* -0.129 0.049 0.0079 0.88 0.80, 0.97
IMP_MAN* -0.453 0.068 <0.0001 0.64 0.56, 0.73
INOPERATIVE -0.247 0.328 0.4508 0.78 0.41, 1.48
LIGHT 0.06 0.049 0.2209 1.06 0.96,1.17
MANEUVER* 0.321 0.041 <0.0001 1.38 1.27, 1.49
MIDDLE_AGED* 0.102 0.043 0.0166 1.11 1.02, 1.20
OLD 0.092 0.14 0.5141 1.10 0.83, 1.44
ONAT_TC* -0.521 0.054 <0.0001 0.60 0.53, 0.66
1.07,
RAIN* 0.33 0.132 0.0124 1.39
1.80
RUTS -0.148 0.224 0.5091 0.86 0.56, 1.34
S_CHAR* -0.114 0.041 0.0051 0.89 0.82, 0.97
S_COND* 0.256 0.056 <0.0001 1.29 1.16, 1.44
S_TYPE* 0.132 0.04 0.0011 1.14 1.05, 1.24
SAFETY_EQUIPT* -1.378 0.075 <0.0001 0.25 0.22, 0.29
SMOG_SAND 0.355 0.218 0.1037 1.43 0.93, 2.19
SNOW 0.151 0.099 0.1261 1.16 0.96, 1.41
SPEED* 0.442 0.054 <0.0001 1.56 1.40, 1.73
SPEED_LIMIT_1* -0.801 0.051 <0.0001 0.45 0.41, 0.50
SPEED_LIMIT_2* -0.39 0.077 <0.0001 0.68 0.58, 0.79
SPEED_LIMIT_3*0.05 level
*- Significant at 0.116 0.052 0.0252 1.12 1.01, 1.24
TRAPPED* 4.417 0.344 <0.0001 82.81 42.21, 162.44
UNATTND 0.483 0.329 0.142 1.62 0.85, 3.09
VSN_OBSTRUCT* -1.326 0.132 <0.0001 0.27 0.21, 0.34
WRONG 0.014 0.058 0.8034 1.01 0.91, 1.14

40. Findings and Conclusions
• More than 80% of fatalities in large truck crashes
are occupants of the “other” vehicles.
• Relatively smaller % of single vehicle fatal truck
crashes, as compared to SV fatal non-truck
crashes.
• Many more…….
• Majority of all truck crashes in KS occurred on
blacktops, in daylight conditions, under no
adverse weather conditions.
• Contributory cause for most truck crashes- driver
related. 73%
• Most common: Failing to give time and
attention, driving too fast for conditions.

41. Findings and Conclusions
• Animal related causes and rain/mist/drizzle more
common among environment related causes.
• Falling cargo, defective tires more common
among vehicle related causes.
• Binary logistic regression provided a good
means to identify the factors leading to increased
severity of truck crashes.

42. • Odds Ratio shows the level of importance.
• Highest odds ratio of 83 - when driver is trapped
– most likely to contribute to increased severity.
• 2.7 times higher odds when driven by person
under the influence of alcohol.
• Many more…
• More focused and targeted countermeasure
ideas/programs developed based on the critical
factors.

43. CREDITS
MATC
Nishitha Bezwada and Siddhartha Kotikalapudi
Mr. Steven Buckley @ KDOT
KDOT and NHTSA
Associate Director at KSU – Dr. Hossain
Slide design © 2009, Mid-America Transportation Center. All rights reserved.

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