This document is available to the public from the National Technical Information Service, Springfield, VA 22161 

U.S. Department 

of Transportation 

National Highway 

Traffic Safety 

Administration 

DOT HS 809 569 June 2003 

Technical Report 

An Analysis of Fatal Large 

Truck Crashes 

Published by: 

National Center for Statistics and Analysis 

Advanced Research and Analysis 

 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 i

1. Report No. 

DOT HS 809 569

2. Government Accession No. 3. Recipient's Catalog No. 

5. Report Date 

March 2003 

4. Title and Subtitle 

An Analysis of Fatal Large Truck Crashes 

6. Performing Organization Code 

NPO-121 

7. Author(s) 

Ramal Moonesinghe, Anders Longthorne, Umesh Shankar, Santohk Singh, 

Rajesh Subramanian, and Joseph Tessmer 

8. Performing Organization Report No. 

9. Performing Organization Name and Address 10. Work Unit No. (TRAIS) 

Mathematical Analysis Division, National Center for Statistics and Analysis 

National Highway Traffic Safety Administration 

U.S. Department of Transportation 

NRD-31, 400 Seventh Street, S.W. 

Washington, D.C. 20590

11. Contract or Grant No. 

13. Type of Report and Period Covered 

NHTSA Technical Report 

12. Sponsoring Agency Name and Address 

Mathematical Analysis Division, National Center for Statistics and Analysis 

National Highway Traffic Safety Administration 

U.S. Department of Transportation 

NRD-31, 400 Seventh Street, S.W. 

Washington, D.C. 20590

14. Sponsoring Agency Code 

15. Supplementary Notes 

Abstract 

The objective of this study by the National Center for Statistics and Analysis (NCSA) was to examine the characteristics of 

large truck fatal crashes. Fatal crashes involving single-unit trucks and combination trucks were studied. Two-vehicle crashes 

consisting of a large truck and one other vehicle were examined for vehicle-related factors and driver-related factors. Using 

data from the Fatality Analysis Reporting System (FARS) 1996-2000 and from the University of Michigan Transportation 

Research Institute’s Trucks Involved in Fatal Accidents Survey (TIFA), characteristics of large truck crashes, including 

rollovers and jackknifes were analyzed. 

17. Key Words 

rollover, jackknife, single-unit trucks, combination 

trucks, large trucks, fatalities, logistic regression, trends 

18. Distribution Statement 

Document is available to the public through the National 

Technical Information Service, Springfield, VA 22161 

http//:www.ntis.gov

19. Security Classif. (of this report) 

Unclassified

20. Security Classif. (of this page) 

Unclassified

21. No. of Pages 

41

22. Price 

Form DOT F 1700.7 (8-72) Reproduction of complete page authorized 

 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 ii
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 iii

Table of Contents 

List of Figures and Tables iv 

EXECUTIVE SUMMARY 

1. INTRODUCTION 1

 

2. TRENDS 2 

3. CHARACTERISTICS OF LARGE TRUCK FATALITIES 7 

4. FATAL LARGE TRUCK CRASHES BY STATE 17 

5. TWO-VEHICLE CRASHES INVOLVING A LARGE TRUCK (FARS) 21 

6. ANALYSIS OF TRUCKS IN FATAL ACCIDENTS (TIFA) 25 

7. PROPENSITY TO ROLL OVER/JACKKNIFE 37 

8. CONCLUSIONS 41 

9. REFERENCES 43 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 iv

List of Figures and Tables 

Figure 1 Large Truck Fatal Involvements....................................................................................4 

Figure 2 Large Truck Fatal Involvements Per 100 Million VMT................................................4 

Figure 3 Large Truck Fatal Involvements Per 100 Thousand Registered Vehicles.....................5 

Figure 4 Relative Risk of Large Truck Fatal Involvement Compared to Passenger Cars 

 Per 100 Million Miles Traveled.....................................................................................5 

Figure 5 Relative Risk of Large Truck Fatal Involvement Compared to Passenger Cars 

 Per 100,000 Registered Vehicles ...................................................................................6 

Figure 6 Large Truck Fatal Crashes as a Percent of All Fatal Crashes........................................6 

Table 1 Fatal Crashes by Truck and Crash Types 1996-2000 ....................................................7 

Table 2 Large Truck Fatalities by Truck Type and Fatality Type 1996-2000............................7 

Table 3 Large Truck Fatalities by Truck Type, Occupant Type, and 

 Period of Week 1996-2000 ............................................................................................8 

Table 4 Large Truck Adjusted Daily Fatality Rate by Truck Type and 

 Fatality Type 1996-2000................................................................................................9 

Table 5 Large Truck Fatalities by Fatality Type and Day vs. Night 1996-2000 ......................10 

Table 6 Large Truck Fatalities by Truck Type, Fatality Type, and 

 Rural vs. Urban 1996-2000..........................................................................................11 

Table 7a Large Truck Fatalities by Truck Type, Fatality Type, Trafficway Division 

 and 2-Lane vs. Other 1996-2000 .................................................................................12 

Table 7b Large Truck Fatalities by Truck Type, Fatality Type, Trafficway Division, 

 and 2-Lane vs. Other 1996-2000 .................................................................................13 

Table 8 Large Truck Fatalities by Truck Type, Fatality Type and 

 No Traffic Controls vs. Any Traffic Control 1996-2000............................................14 

Table 9 Large Truck Fatalities by Truck Type, Fatality Type and 

 Relation to Junction 1996-2000...................................................................................15 

Table 10 Large Trucks Involved in Fatal Crashes by Truck Type and State 1996-2000 ...........18 

Table 11 Fatal Tuck Involvements per 1,000 Miles of Public Road Length 

 by State 1996-2000 ......................................................................................................20 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 v

Table 12 Impact Points for Two-Vehicle Large Truck Crashes by Truck Type 1996-2000......21 

Table 13 Related Factors for Two-Vehicle Large Truck Crashes by Truck Type 

 and Vehicle Type 1996-2000.......................................................................................22 

Table 14 Two-Vehicle Large Truck Crashes by Driver-Related Factors, Truck Type 

 and Vehicle Type 1996-2000.......................................................................................24 

Table 15a Two-Vehicle Combination Truck Fatalities by Crash Type 1996-1999 .....................26 

Table 15b Two-Vehicle Single Truck Fatalities by Crash Type 1996-1999 ................................27 

Table 16 Large Truck Fatalities by Truck Type, Fatality Type, and 

 Hours Driven Before the Crash 1996-1999 .................................................................28 

Table 17 Fatalities by Trip Distance for Large Truck Crashes by Truck Type 

 and Fatality Type 1996-1999.....................................................................................29 

Table 18 Large Truck Fatalities by Truck Type, Fatality Type and Rollover 1996-1999..........30 

Table 19 Mean Gross Weight (lbs) of Large Trucks by Truck Type, Crash Type, 

 Number of Trailers, and Rollover 1996-1999.............................................................31 

Table 20 Mean Unit Length of Large Trucks by Truck Type, Fatality Rate, 

 and Length in Feet 1996-1999 ....................................................................................32 

Table 21 Combination Truck Fatalities by Fatality Type and 

 Relation of Trailer Length 1996-1999 .........................................................................33 

Table 22 Large Truck Fatalities 1996-1999................................................................................34 

Table 23 Combination Truck Fatalities by Occupant Type and Number of Trailers 

 1996-1999 ....................................................................................................................34 

Table 24 Mean Gross Weight (lbs) of Units for Combination Trucks 

 by Type of Crash, Number of Trailers, and Jackknife 1996-1999 .............................35 

Table 25 Large Truck Fatalities by Truck Type, Fatality Type and 

 Sideswipe Direction 1996-1999..................................................................................36 

Table 26 Variables Used for Inclusion in Rollover and Jackknife Rate Models........................38 

Table 27 Rollover Propensity of Single-unit Trucks 

 Multivariate Analysis-Logit Model Results 1996-1999 .............................................39 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 vi

Table 28 Rollover Propensity of Combination Trucks 

 Multivariate Analysis-Logit Model Results 1996-1999 .............................................39 

Table 29 Jackknife Propensity of Combination Trucks 

 Multivariate Analysis-Logit Model Results 1996-1999 .............................................40 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 

EXECUTIVE SUMMARY 

In 2000, there were 4,9301

 large trucks involved in fatal crashes, 101,000 large trucks involved 

in injury crashes, and 351,000 large trucks involved in property damage-only crashes for a total 

of 457,000 large trucks involved in crashes. Large trucks are defined as trucks with a gross 

vehicle weight of at least 10,000 pounds. 

Since the late 1970s, approximately 12 to 13 percent of all traffic-related fatal crashes were the 

result of a crash involving a large truck; see Figure 6, pg. 6. 

Large truck fatalities are classified as occupant fatalities in single-vehicle crashes or multiplevehicle crashes and non–occupant fatalities. Single-vehicle fatalities, multiple-vehicle fatalities, 

and non-occupant fatalities in combination truck crashes account for 7 percent, 63 percent and 6 

percent, respectively, of all large truck fatalities. By comparison, the portion of all large truck 

fatalities associated with single-unit trucks are 2 percent, 20 percent, and 2 percent for singlevehicle, multiple-vehicle and non-occupant fatalities, respectively; see Table 2 pg. 7. 

Just over half of all large truck fatalities occur on non-divided 2-lane roadways, that is, 

conventional 2-lane roads with one lane in each direction; see Table 7b pg. 13. 

Analysis of geometrical data was used to analyze two-vehicle crashes involving a large truck. 

The data suggest that for some types of crashes, the driver of the other vehicle may have 

contributed more to the crash than did the driver of the large truck; see Tables 15a and 15b pgs. 

26-27. 

A speed limit of 55 mph or higher, poor weather, and a curved road significantly increase the 

odds of both a rollover and a jackknife for large trucks. As the weight of the large truck and its 

cargo increases, the odds of a rollover increase, but the odds of a jackknife decrease. 

Conversely, as the length of a large truck increases, the odds of a rollover decrease, but the odds 

of a jackknife increase; see Tables 27, 28, and 29, pgs.39-40. 

 

1 As Reported in Traffic Safety Facts 2000
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 1

1. INTRODUCTION 

Crashes involving large trucks are a serious traffic safety problem. In 2000, there were 4,930 

large trucks involved in fatal crashes, 101,000 large trucks involved in injury crashes, and 

351,000 large trucks involved in property damage-only crashes for a total of 457,000 large trucks 

involved in all crashes. Large trucks are defined as trucks with a gross vehicle weight of at least 

10,000 pounds. 

 

Large trucks are partitioned into two main subsets, single-unit trucks and combination trucks. A 

single-unit truck (SUT) is a truck without a trailer. A common example of a single-unit truck is 

the familiar United Parcel Service (UPS) truck. A combination truck is a truck that tows another 

vehicle, such as tractor trailers. By convention, a tractor by itself, often called a “bobtail”, is 

considered a combination truck. In addition, if a single-unit truck tows another vehicle, it is a 

combination truck. 

The Fatality Analysis Reporting System (FARS) and the Trucks Involved in Fatal Accidents 

survey (TIFA) were the sources of data for this analysis. FARS consists of a census of all fatal 

crashes that occurred on a public roadway, and is not a representative sample of all crashes on 

US roadways. Fatalities are included in FARS if they occur within 30 days of the crash to which 

they are associated. 

The TIFA survey is conducted by the Center for National Truck Statistics at the University of 

Michigan Transportation Research Institute. The file contains a random sample of large trucks, 

specifically straight trucks without trailers and tractor trailers (as recorded in FARS), that were 

involved in a fatal crash within the United States. TIFA data collection is augmented through 

telephone interviews with individuals who have knowledge of the truck at the time of the crash. 

Interviews are typically carried out with the driver, owner, safety director of the carrier operating 

the truck, the reporting police officer, and other involved parties. The combination of the FARS 

records and the additional data collected by these telephone interviews forms the TIFA file. The 

most recent TIFA data are from 1999. 

TIFA also includes geometrical information, which can be used to classify two-vehicle crashes 

between a large truck and a passenger vehicle. These classified crashes help to determine which 

vehicle contributed more to the crash. For example, there were 1,696 fatalities in head-on 

crashes involving a large combination truck and a passenger vehicle where the passenger vehicle 

was in the combination truck’s lane. There were only 177 fatalities in head-on crashes involving 

a large combination truck and a passenger vehicle where the combination truck was in the 

passenger vehicle’s lane: see (Tables 15a and 15b) pgs. 26-27. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 2
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 3

2. TRENDS

Since the inception of FARS in 1975, the number of large truck fatal involvements had a 

minimum value of 3,977 in 1975 and a maximum of 6,084 in 1979. In 2000 4,930 large trucks 

were involved in fatal crashes; see Figure 1 pg 4. 

Since 1989, the number of large trucks involved in fatal crashes has ranged from 4,035 in 1992 

to 4,984 in 1989. To gain additional insight, the raw data of Figure 1 are adjusted by the vehicle 

miles traveled, (VMT), Figure 2, pg 4 and number of registered vehicles, Figure 3, pg5. In both 

cases there is a general downward trend since 1979. 

From Figures 2 and 3 one sees that the number of large trucks involved in fatal crashes when 

adjusted for VMT or registered vehicles has been declining since 1979. Over the past twenty 

years, many improvements have been made in traffic safety contributing to the 

observed reductions seen in Figures 2 and 3. 

The data of Figures 2 and 3 also exist for passenger cars. The relative risk2

 of large truck fatal 

involvements compared to passenger cars appears in Figures 4 and 5 pgs 5 and 6.. When the 

data are adjusted by VMT, Figure 4, one sees that the relative risk of a crash involving a large 

truck compared to a passenger car is 1.20 to 1.55. In other words, large trucks are 20 percent to 

55 percent more likely to be involved in a fatal crash than a passenger car. Note that between 

1975 and 1985 the relative risk is generally above 1.4, but between 1986 and 2000 the relative 

risk is generally below 1.4. 

When adjusting for the number of registered vehicles, one sees that the relative risk of a crash 

involving a large truck, compared to a passenger car, is two to three times as great. 

Figure 6, pg 6, shows the percent of large truck fatal crashes as a percent of all fatal crashes. 

Since the late 1970s, approximately 12 to 13 percent of all traffic-related fatal crashes are the 

result of a crash involving a large truck. Figures 5 and 6 suggest that the decrease in fatalities 

associated with large trucks may be due to the overall improvement in highway safety. 

 

2 The relative risk is defined as ((number of large truck fatal involvements ÷ number of registered large trucks) ÷ 

(number of passenger car fatal involvements ÷ number of registered passenger cars)). 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 4

Figure 1. Large Truck Fatal Involvements

3000

3500

4000

4500

5000

5500

6000

6500

1975197719791981198319851987198919911993199519971999

Source: NHTSA, NCSA, FARS 1975-2000

 

Figure 2. Large Truck Fatal Involvements Per 

100 Million VMT

2

2.5

3

3.5

4

4.5

5

5.5

6

1975197719791981198319851987198919911993199519971999

Source: NHTSA, NCSA, FARS, and FHWA, VMT data 1975-2000
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 5

Figure 3. Large Truck Fatal Involvements

Per 100,000 Registered Vehicles

60

65

70

75

80

85

90

95

100

105

110

1975197719791981198319851987198919911993199519971999

Source: NHTSA, NCSA, FARS 1975-2000

Figure 4. Relative Risk of Large Truck Fatal Involvement 

Compared to Passenger Cars 

Per 100 Million Miles Traveled 

1.1

1.15

1.2

1.25

1.3

1.35

1.4

1.45

1.5

1.55

1.6

1975197719791981198319851987198919911993199519971999

Source: NHTSA, NCSA, FARS, and FHWA, VMT data 1975-2000
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 6

Figure 5. Relative Risk of Large Truck Fatal Involvement 

Compared to Passenger Cars

Per 100,000 Registered Vehicles

1.8

2

2.2

2.4

2.6

2.8

3

3.2

1975197719791981198319851987198919911993199519971999

Source: NHTSA, NCSA, FARS 1975-2000

Figure 6. Large Truck Fatal Crashes as a 

Percent of All Fatal Crashes

8

9

10

11

12

13

14

1975197719791981198319851987198919911993199519971999

Source: NHTSA, NCSA, FARS 1975-2000
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 7

3. CHARACTERISTICS OF LARGE TRUCK FATALITIES 1996-2000

The portion of large truck single-vehicle crashes to all large truck crashes is much smaller than 

the portion of single-vehicle crashes involving other vehicles. Over the five year period, 1996-

2000, one out of six large truck crashes, 18 percent, is a single-vehicle crash, whereas 62 percent 

of crashes not involving a large truck are single-vehicle crashes. 

Table 1 

Fatal Crashes by Truck and Crash Types 1996-2000

Crash Type

Truck Type Single Multiple Total % Single % Multiple

Vehicle Vehicle Vehicle Vehicle 

 Large Truck Crashes 4,057 18,628 22,685 18% 82% 

 Non-Large Truck Crashes 100,747 63,042 163,789 62% 38% 

 Total 104,804 81,670 186,474 56% 44% 

 Source: NHTSA, NCSA, FARS 

Fatalities due to large truck crashes may be partitioned into three distinct types: occupant 

fatalities of single-vehicle crashes, occupant fatalities of multiple-vehicle crashes, and nonoccupant fatalities, i.e., a pedestrian or a cyclist is killed. In the remainder of this report, these 

crash fatalities will be referenced as Single-vehicle, Multiple-vehicle, and Non-Occupant 

fatalities. The distribution of large truck fatalities by this partition appears in Table 2. 

Approximately 90 percent (= 22,462/(22,462+2,460)) of occupant fatalities in large truck fatal 

crashes occur in multiple-vehicle crashes. 

Table 2 

Large Truck Fatalities by Truck Type and Fatality Type 1996-2000

Fatality Type

Truck Type Single Multiple Non % Single % Multiple % Non 

 Vehicle Vehicle Occupant Vehicle Vehicle Occupant

 

 Combination Trucks 1,790 17,066 1,431 7% 63% 6% 

 Single-unit Trucks 670 5,396 642 2% 20% 2% 

 Total 2,460 22,462 2,073 9% 83% 8% 

 Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 8

The 1996-2000 FARS data for large trucks are partitioned by day of the week, Saturday-Sunday 

and Monday-Friday; see Table 3. Fatality type is partitioned into non-occupant fatalities and 

occupant fatalities. Most large truck crashes with a non-occupant fatality do not have any other 

type of fatality. Most large truck non-occupant fatalities are usually pedestrians or cyclists. 

Large truck crashes involving an occupant fatality have different characteristics than nonoccupant fatality crashes. Occupant fatalities have been sup-partitioned into single-vehicle 

crashes and multiple-vehicle crashes due to the different characteristics of large truck singlevehicle crashes and multiple-vehicle crashes. 

A smaller portion of large combination truck occupant fatalities occur from Monday to Friday 

(about 83 percent) than the portion of large single-unit truck fatalities (about 88 percent). The 

difference between large truck occupant fatalities and large truck non-occupant fatalities is 

consistent across truck types, i.e., combination trucks and single-unit trucks. 

Table 3 

Large Truck Fatalities by Truck Type, Occupant Type, 

and Period of Week 1996-2000 

Combination Trucks-Combined Day of Week

Fatality Type Sat+Sun Mon-Fri Total Sat+Sun(%) Mon-Fri(%) 

 

Occupant

Single-vehicle 312 1,478 1,790 17% 83%

Multiple-vehicle 2,952 14,114 17,066 17% 83%

Total 3,264 15,592 18,856 17% 83%

 

Non-Occupant 248 1,183 1,431 17% 83%

Single-unit Trucks-Combined Day of Week

Fatality Type Sat+Sun Mon-Fri Total Sat+Sun(%) Mon-Fri(%) 

Occupant 

Single-vehicle 90 580 670 11% 89%

Multiple-vehicle 651 4,745 5,396 12% 88%

Total 741 5,325 6,066 12% 88%

 

Non-Occupant 72 570 642 11% 89%

 Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 9

The adjusted daily fatality rate, is computed by dividing the Sat+Sun period column of Table 3, 

by 520 (=2 days of the week times 52 weeks per year times 5 years) and dividing the Mon-Fri 

period column, of Table 3, by 1,300 (= 5 days of the week times 52 weeks per year times 5 

years). Table 4 is the result. The adjusted daily fatality rate for combination trucks is 

approximately twice as high for Mon-Fri period compared to the Sat+Sun period. For single-unit 

trucks, the Mon-Fri period adjusted daily fatality rate is almost three times as high as the 

Sat+Sun period rate. 

Table 4 

Large Truck Adjusted Daily Fatality Rate 

by Truck Type and Fatality Type 1996-2000 

Combination Trucks

Fatality Type Sat+Sun Mon-Fri 

Occupant

Single-vehicle 0.60 1.14

Multiple-vehicle 5.68 10.86

Total 6.28 11.99

Non-Occupant 0.48 0.91

Single-unit Trucks

Fatality Type Sat+Sun Mon-Fri 

Occupant

Single-vehicle 0.17 0.45

Multiple-vehicle 1.25 3.65

Total 1.42 4.10

Non-Occupant 0.14 0.44

Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 10

The “Day” partition is determined by the light condition and refers to daylight, dawn or dusk. 

The “Night” partition refers to night and night but lighted. 

Single-unit trucks are more likely to have crashes during the day, by about 19 percent, than 

combination trucks. This is true for all crash groups; see Table 5. 

Table 5 

Large Truck Fatalities by Fatality Type and Day vs. Night 

1996-2000

Combination Trucks-Day vs. Night

Fatality Type Day Night Total Day(%) Night(%) 

 

Occupant

Single-vehicle 1,000 790 1,790 56% 44%

Multiple-vehicle 11,097 5,969 17,066 65% 35%

Total 12,097 6,759 18,856 64% 36%

Non-Occupant 757 674 1,431 53% 47%

Single-unit Trucks-Day vs. Night

Fatality Type Day Night Total Day(%) Night(%) 

Occupant

Single-vehicle 473 169 642 81% 19%

Multiple-vehicle 4,479 917 5,396 83% 17%

Total 4,952 1,086 6,038 82% 18%

Non-Occupant 545 125 670 74% 26%

Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 11

The FARS crash data are partitioned by crash location, rural and urban, using data provided by 

the Federal Highway Administration. Larger portions of combination truck fatalities occur in 

rural areas (71 percent) than single-unit truck fatalities (60 percent). The data show that 

approximately 3 out of 4 large truck single-vehicle occupant fatalities occur in rural areas, (79 

percent for single-vehicle, combination truck fatalities and 74 percent for single-vehicle, singleunit truck fatalities). There is a shift away from rural crashes where non-occupants are 

concerned. Less than half of the non-occupant fatalities involving combination trucks, 45 

percent, occur in rural areas. The rural non-occupant fatalities involving single-unit trucks drops 

to 26 percent. 

Table 6 

Large Truck Fatalities By Truck Type, Fatality Type, and Rural vs. Urban 

1996-2000

Combination Trucks

Fatality Type Rural Urban Total Rural(%) Urban(%) 

 

Occupant 

Single-vehicle 1,397 376 1,773 79% 21%

Multiple-vehicle 12,306 4,644 16,950 73% 27%

Total 13,703 5,020 18,723 73% 27%

 

Non-Occupant 633 789 1422 45% 55%

Grand Total 14,336 5,809 20,145 71% 29%

Single-unit Trucks

Fatality Type Rural Urban Total Rural(%) Urban(%) 

 

Occupant 

Single-vehicle 491 178 669 74% 26%

Multiple-vehicle 3,314 2,035 5.349 62% 38%

Total 3,805 2,213 6,018 63% 37%

 

Non-Occupant 163 475 638 26% 74%

Grand Total 3,968 2,688 6,656 60% 40%

 Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 12

Almost half, 48 percent, of fatalities involving combination trucks occur on non-divided 2-lane 

trafficways3

, that is, conventional 2-lane roads with one lane in each direction. 

Table 7a 

Large Truck Fatalities by Truck Type, Fatality Type, Trafficway Division, 

and 2-Lane vs. Other 1996-2000

Combination Trucks 

 

Fatality Type Division 2-Lane Other Total 2-Lane(%) Other(%) Total(%) 

Occupant 

Single-vehicleNot Divided 748 50 798 42% 3% 45%

Divided 683 299 982 38% 17% 55%

Total 1,431 349 1,780 80% 20% 100%

Occupant 

Multiple-vehicleNot Divided 8,464 1,017 9,481 50% 6% 56%

Divided 4,592 2,889 7,481 27% 17% 44%

Total 13,056 3,906 16,962 77% 23% 100%

Non-Occupant 

Not Divided 448 127 575 32% 9% 41%

Divided 458 372 830 33% 26% 59%

Total 906 499 1,405 65% 35% 100%

Combination Trucks

Not Divided 9,660 1,194 10,854 48% 6% 54%

Divided 5,733 3,560 9,293 28% 18% 46%

Total Combination Trucks 15,393 4,754 20,147 76% 24% 100%

 Source: NHTSA, NCSA, FARS 

 

3 Roadways are defined as a continuous cross section of pavement but do not include the shoulders. Trafficways 

are from right-of-way to right-of-way and may have one or more roadways and include the shoulders. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 13

Just over half of all large truck fatalities and 59 percent of all large single-unit truck fatalities 

occur on non-divided 2-lane roadway, that is, conventional 2-lane roads with one lane in each 

direction. 

Table 7b 

Large Truck Fatalities by Truck Type, Fatality Type, Trafficway Division, 

and 2-Lane vs. Other 1996-2000

Single-unit Trucks 

 

Fatality Type Division 2-Lane Other Total 2-Lane(%) Other(%) Total(%)

Occupant 

Single-vehicleNot Divided 447 15 462 68% 2% 70%

Divided 124 76 200 19% 11% 30%

Total 571 91 662 86% 14% 100%

Occupant 

Multiple-vehicleNot Divided 3,184 428 3,612 59% 8% 67%

Divided 975 773 1,748 18% 14% 32%

Total 4,159 1,201 5,360 77% 22% 100%

Non-Occupant 

Not Divided 298 110 408 47% 18% 65%

Divided 100 119 219 16% 19% 35%

Total 398 229 627 63% 37% 100%

Single-unit Trucks

Not Divided 3,929 553 4,482 59% 8% 67%

Divided 1,199 968 2,167 18% 15% 33%

Total Single-unit Trucks 5,128 1,521 6,649 77% 23% 100%

All Large Trucks 

Not Divided 13,589 1,747 15,336 51% 7% 57%

Divided 6,932 4,528 11,460 26% 17% 43%

Grand Total All Large Trucks 20,521 6,275 26,796 77% 24% 100%

 Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 14

A partial list of traffic control devices includes: traffic lights, warning/flashing lights, stop signs, 

yield signs, warning signs, school signs, officers, crossing guards, and flagmen. The portion of 

combination truck fatalities at traffic controls (27 percent) is less than the portion of single-unit 

truck fatalities at traffic controls (33 percent). The approximate 7 percent difference in fatalities 

is constant for crash types: multi-vehicle and non-occupant. 

Table 8 

Large Truck Fatalities by Truck Type, Fatality Type and 

No Traffic Controls vs. Any Traffic Control 1996-2000

Combination Trucks

Fatality Type No Controls Any Controls Total No Controls(%) Any Controls(%)

 

Occupant 

Single-vehicle 1,511 279 1,790 84% 16%

Multiple-vehicle 12,222 4,844 17,066 72% 28%

Total 13,733 5,123 18,856 73% 27%

 

Non-Occupant 1,117 314 1,431 78% 22%

Single-unit Trucks

Fatality Type No Controls Any Controls Total No Controls(%) Any Controls(%)

 

Occupant

Single-vehicle 113 670 83% 17%

Multiple-vehicle 

557 

3,506 1,890 5,396 65% 35%

Total 4,063 2,003 6,066 67% 33%

 

Non-Occupant 448 194 642 70% 30%

 Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 15

Junctions are intersections, driveways, ramps, crossings, etc. Approximately 80 percent of large 

truck single-vehicle crashes, both combination trucks and single-unit trucks, occur away from a 

junction. The percent of fatalities of single-unit trucks for both multi-vehicle related fatalities 

and non-occupant fatalities is 8 to 9 percent lower than the corresponding percent for 

combination trucks. 

Table 9 

Large Truck Fatalities by Truck Type, Fatality Type and 

Relation to Junction 1996-2000

Combination Trucks

Fatality Type Non-Junction Any Junction Total Non-Junction(%) Any Junction(%) 

 

Occupant 

Single-vehicle 1,431 359 1,790 80% 20%

Multiple-vehicle 10,733 6,330 17,063 63% 37%

Total 12,164 6,689 18,853 65% 35%

 

Non-Occupant 1,007 424 1,431 70% 30%

Single-unit Trucks

Fatality Type Non-Junction Any Junction Total Non-Junction(%) Any Junction(%) 

 

Occupant 

Single-vehicle 564 106 670 84% 16%

Multiple-vehicle 2,994 2,402 5396 55% 45%

Total 3,558 2,508 6,066 59% 41%

 

Non-Occupant 394 247 641 61% 39%

 Source: NCSA, NHTSA, FARS 

 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 16
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 17

4. FATAL LARGE TRUCK CRASHES BY STATE 

Table 10 lists the frequency of large trucks involved in fatal crashes by state from 1996 to 2000. 

Eleven states account for 51 percent of the combination trucks involved in fatal crashes, and ten 

states account for 52 percent of the single-unit trucks involved in fatal crashes. Texas had more 

combination trucks involved in fatal crashes than any other state. However, Texas also has more 

miles of public roads than any other state, 300,507 miles; see Table 11. 

A coding problem in the classification of large trucks may exist within the FARS data. Note, for 

example, the case of Mississippi, in Table 10, which reports 522 large combination truck fatal 

crashes, but only 2 single-unit truck crashes. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 18

Table 10 

Large Trucks Involved in Fatal Crashes by Truck Type and State 1996-2000 

Combination Trucks Single-unit Trucks 

State No. Veh. Cum. %Total State No. Veh. Cum %Total

1 TEXAS 1,639 1,639 8.9% FLORIDA 484 484 8.0%

2 CALIFORNIA 1,337 2,976 7.2% CALIFORNIA 446 930 7.4%

3 FLORIDA 1,021 3,997 5.0% TEXAS 437 1,367 7.3%

4 OHIO 775 4,772 4.8% NEW YORK 327 1,694 5.3%

5 GEORGIA 749 5,521 4.0% GEORGIA 305 1,999 5.2%

6 NORTH CAROLINA 709 6,230 3.9% PENNSYLVANIA 288 2,287 4.7%

7 INDIANA 674 6,904 3.6% NORTH CAROLINA 244 2,531 4.1%

8 ILLINOIS 673 7,577 3.6% OHIO 203 2,734 3.4%

9 PENNSYLVANIA 651 8,228 3.6% MICHIGAN 192 2,926 3.1%

10 ALABAMA 621 8,849 3.5% INDIANA 183 3,109 3.1%

11 TENNESSEE 592 9,441 3.2% ILLINOIS 182 3,291 3.0%

12 MISSOURI 588 10,029 3.2% KENTUCKY 179 3,470 3.0%

13 MISSISSIPPI 522 10,551 2.8% MISSOURI 176 3,646 2.4%

14 MICHIGAN 519 11,070 2.8% TENNESSEE 161 3,807 2.7%

15 LOUISIANA 469 11,539 2.6% VIRGINIA 158 3,965 2.5%

16 SOUTH CAROLINA 458 11,997 2.5% NEW JERSEY 142 4,107 2.4%

17 ARKANSAS 451 12,448 2.5% WISCONSIN 134 4,241 2.3%

18 NEW YORK 409 12,857 2.2% ALABAMA 133 4,374 2.2%

19 VIRGINIA 398 13,255 2.2% MARYLAND 124 4,498 2.0%

20 OKLAHOMA 393 13,648 2.1% LOUSIANA 119 4,617 2.0%

21 ARIZONA 376 14,024 2.0% WASHINGTON 110 4,727 1.8%

22 IOWA 328 14,352 1.8% IOWA 97 4,824 1.7%

23 KENTUCKY 311 14,663 1.7% MINNESOTA 90 4,914 1.5%

24 KANSAS 306 14,969 1.6% OKLAHOMA 87 5,001 1.5%

25 MINNESOTA 303 15,272 1.6% ARIZONA 81 5,082 1.3%

26 WISCONSIN 302 15,574 1.6% MASSACHUSETTS 80 5,162 1.3%

27 OREGON 239 15,813 1.3% COLORADO 78 5,240 1.3%

28 NEW JERSEY 238 16,051 1.3% KANSAS 76 5,316 1.3%

29 COLORADO 229 16,280 1.2% OREGON 71 5,387 1.2%

30 WASHINGTON 229 16,509 1.2% WEST VIRGINIA 67 5,454 1.1%

31 MARYLAND 220 16,729 1.2% ARKANSAS 66 5,520 1.1%

32 NEW MEXICO 205 16,934 1.1% CONNECTICUT 58 5,578 0.9%

33 NEBRASKA 198 17,132 1.1% SOUTH CAROLINA 57 5,635 0.9%

34 WEST VIRGINIA 181 17,313 0.9% MAINE 46 5,681 0.8%

35 UTAH 176 17,489 0.9% NEBRASKA 46 5,727 0.8%

36 NEVADA 143 17,632 0.8% IDAHO 37 5,764 0.6%

37 MASSACHUSETTS 111 17,743 0.6% NEVADA 35 5,799 0.6%

38 IDAHO 106 17,849 0.6% NEW MEXICO 34 5,833 0.6%

39 WYOMING 96 17,945 0.5% UTAH 33 5,866 0.6%

40 CONNECTICUT 84 18,029 0.4% SOUTH DAKOTA 26 5,892 0.5%

41 MONTANA 77 18,106 0.4% MONTANA 23 5,915 0.4%

42 SOUTH DAKOTA 61 18,167 0.4% DELAWARE 22 5,937 0.4%

43 DELAWARE 59 18,226 0.3% VERMONT 18 5,955 0.3%

44 MAINE 58 18,284 0.3% NEW HAMPSHIRE 15 5,970 0.3%

45 NORTH DAKOTA 54 18,338 0.3% RHODE ISLAND 15 5,985 0.3%

46 NEW HAMPSHIRE 38 18,376 0.2% WYOMING 12 5,997 0.2%

47 VERMONT 32 18,408 0.2% HAWAII 10 6,007 0.2%

48 ALASKA 16 18,424 0.1% ALASKA 8 6,015 0.2%

49 HAWAII 12 18,436 0.1% WASHINGTON, DC 6 6,021 0.1%

50 WASHINGTON, DC 7 18,443 0.0% NORTH DAKOTA 5 6,026 0.1%

51 RHODE ISLAND 6 18,449 0.0% MISSISSIPPI 2 6,028 0.0%

Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 19

For each state, Table 11 lists the number of large trucks involved in fatal crashes, the miles of 

public road, and the annual rate of large trucks involved in fatal crashes per 1,000 miles of public 

road. California, Delaware, Florida, Georgia, Louisiana, Maryland, New Jersey, and North 

Carolina, all have a large number of trucks involved in fatal crashes and an annual rate of at least 

1.9 trucks involved in fatal crashes per 1,000 miles of public road. The number of vehicle miles 

traveled, VMT, for large trucks is not available by state, which means that the popular measure 

of fatal crashes per 100 million vehicle miles traveled cannot be calculated. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 20

Table 11 

Fatal Truck Involvements per 

1,000 Miles of Public Road Length by State 1996-2000

State No. Vehicles Public Road Length Annualized Rate/1000 Miles

1 DELAWARE 81 5,747 2.8 

2 FLORIDA 1,505 115,956 2.6 

3 MARYLAND 344 30,322 2.3 

4 CALIFORNIA 1,783 166,973 2.1 

5 NEW JERSEY 380 35,941 2.1 

6 LOUISIANA 588 60,828 1.9 

7 NORTH CAROLINA 953 99,302 1.9 

8 GEORGIA 1,054 113,894 1.9 

9 INDIANA 857 93,605 1.8 

10 WASHINGTON, DC 13 1,425 1.8 

11 TENNESSEE 753 87,259 1.7 

12 ARIZONA 457 54,454 1.7 

13 OHIO 978 116,371 1.7 

14 ALABAMA 754 94,247 1.6 

15 PENNSYLVANIA 939 119,384 1.6 

16 VIRGINIA 556 70,327 1.6 

17 SOUTH CAROLINA 515 64,901 1.6 

18 MISSISSIPPI 524 73,318 1.4 

19 TEXAS 2,076 300,507 1.4 

20 CONNECTICUT 142 20,788 1.4 

21 WEST VIRGINIA 248 36,339 1.4 

22 KENTUCKY 49 74,121 1.3 

23 NEW YORK 736 112,659 1.3 

24 ILLINOIS 855 138,246 1.2 

25 MISSOURI 764 122,831 1.2 

26 MICHIGAN 711 121,722 1.2 

27 MASSACHUSETTS 191 35,265 1.1 

28 ARKANSAS 517 97,562 1.1 

29 HAWAII 22 4,257 1.0 

30 NEVADA 178 35,871 1.0 

31 UTAH 209 41,456 1.0 

32 MAINE 104 22,664 0.9 

33 OREGON 310 66,879 0.9 

34 OKLAHOMA 480 112,511 0.9 

35 WASHINGTON 339 80,256 0.8 

36 NEW MEXICO 239 59,913 0.8 

37 WYOMING 108 26,777 0.8 

38 WISCONSIN 436 111,906 0.8 

39 IOWA 425 112,904 0.8 

40 COLORADO 307 85,149 0.7 

41 NEW HAMPSHIRE 53 15,173 0.7 

42 VERMONT 50 14,265 0.7 

43 RHODE ISLAND 21 6,052 0.7 

44 IDAHO 143 45,802 0.6 

45 MINNESOTA 393 131,996 0.6 

46 KANSAS 382 133,963 0.6 

47 NEBRASKA 244 92,798 0.5 

48 ALASKA 24 12,667 0.4 

49 MONTANA 100 64,662 0.3 

50 SOUTH DAKOTA 87 83,410 0.2 

51 NORTH DAKOTA 59 86,615 0.1 

Source: NHTSA, NCSA, FARS 

 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 21

5. TWO-VEHICLE CRASHES INVOLVING A LARGE TRUCK (FARS) 

Over 95 percent of two-vehicle crashes involving a large truck involve either the front of the 

truck and/or the front of the other vehicle. The point of impact of the large truck is the front of 

the truck in approximately two out of three two-vehicle crashes involving a large truck. About 

half of these crashes are front-to-front crashes. 

Table 12 

Impact Points for Two-Vehicle Large Truck Crashes by Truck Type 

1996-2000 

Combination Trucks 

 Impact Point of -------------------Impact Point of the Other Vehicle--------------- 

 the Comb. Truck Front Side Rear % Front % Side % Rear Total 

 Front 3,219 2,894 778 30% 27% 7% 64% 

 Side 1,648 230 35 15% 2% 0% 17% 

 Rear 1,755 80 25 16% 2% 0% 18% 

 Total 6,622 3,204 838 61% 31% 7% 100% 

Single-unit Trucks 

 Impact Point of ------------------Impact Point of the Other Vehicle---------------- 

 the SUT Front Side Rear % Front % Side % Rear Total 

 Front 1,223 1,199 174 34% 33% 5% 72% 

 Side 346 50 6 10% 1% 0% 11% 

 Rear 577 31 6 16% 1% 0% 17% 

Total 2,146 1,280 186 60% 35% 5% 100% 

 Source: NHTSA, NCSA, FARS 

 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 22

Within the police accident report, officers can refer to the condition of vehicle components, i.e., 

the vehicle-related factors. The report may indicate that a component is inadequate, inoperative, 

faulty, damaged or defective. The condition may be due to owner/user neglect, poor or substandard maintenance, tampering or defective manufacturing. The vehicle-related factor(s) noted, 

within the police accident report, indicates the existence of the condition(s). The condition may 

or may not have played a role in the crash. The table below is for two-vehicle crashes consisting 

of a large truck and one other vehicle. 

The first sub-table provides data on any reported vehicle-related factors. The brake system data, 

of the second sub-table, is a proper subset of any vehicle-related factor. Looking at any vehiclerelated factors, one notes that 70 percent of the reported vehicle factors, cited by the investigating 

officer, were attributed to a large truck. However, there were only 833 factors listed for twovehicle crashes involving a large truck from 1996 to 2000. In the special case of brake system 

citations, 86 percent of the reported brake system vehicle factors were attributed to a large truck. 

It is of interest to compare Table 13 with Tables 14, 15a and 15b. Table 13 reports on 

mechanical problems cited. Most of the citations are against the truck. This, in part, may be due 

to the vigilance of the investigating officer. 

Table 13 

Related Factors for Two-Vehicle Large Truck Crashes by 

Truck Type and Vehicle Type 1996-2000

Any Vehicle-Related Factor

 

Truck type Truck Other Total Truck(%) Other(%) 

 

Combination 388 216 604 64% 36%

Single-unit 160 69 229 77% 23%

Total 548 285 833 70% 30%

Brake System

 

Truck type Truck Other Total Truck(%) Other(%) 

 

Combination 193 30 223 87% 13%

Single-unit 69 11 80 86% 14%

Total 262 41 303 86% 14%

 Source: NHTSA, NCSA, FARS 

On the other hand, Tables 14, 15a and 15b report on actions taken by the drivers of the vehicle. 

These four tables examine two independent parts of large truck crashes, namely maintenance and 

driver actions. There does not appear to be an association between the two. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 23

Related factors are also collected for drivers involved in fatal crashes. The data of Table 14 are 

for two-vehicle crashes involving a large truck and another vehicle. The first sub-table provides 

data for any driver-related factor. The following three sub-tables provide similar data for the 

driver-related factors of speeding, drowsy/asleep/inattentive, and failure to yield. These three 

sub-tables are mutually exclusive proper subsets of the set of any driver-related factors. 

Considering any driver-related factor, one notes that 26 percent of the citations are attributed to 

the drivers of the large trucks. Similarly, the portion of factors attributed to speeding, drowsy/ 

asleep/inattentive, and failure to yield, are 22 percent, 20 percent, and 24 percent, respectively. 

Regardless of the variable examined, the driver of the other vehicle, that is the non-large truck 

vehicle, has the preponderance of driver-related factors cited. For example, 74 percent for any 

driver-related factor is coded for the other vehicle. 

The TIFA survey is conducted by the Center for National Truck Statistics at the University of 

Michigan Transportation Research Institute. The file contains a random sample of large trucks, 

specifically straight trucks without trailers and tractor trailers (as recorded in FARS) that were 

involved in a fatal crash in the United States. 

The TIFA data collection is accomplished through a detailed examination of the police accident 

report and telephone interviews with individuals who have knowledge of the truck at the time of 

the crash. Interviews are typically carried out with the driver, owner, safety director of the carrier 

operating the truck, the reporting police officer, and other involved parties. The combination of 

the FARS records, the police accident report, and the additional data collected by these telephone 

interviews forms the TIFA file. The most recent TIFA data are from 1999. 

Crashes involving large trucks often leave physical evidence. Some of this physical evidence is 

captured in the TIFA crash data, which is not dependent on the reports of the driver or any other 

individual. In many fatal crashes, the point of impact combined with the relative position of the 

vehicles, suggests that one driver contributed more to the crash than the other driver; for example, 

a head-on crash in which one vehicle is in its proper lane and the other vehicle is not. For the 

purpose of analysis, it is reasonable to assume that the principal contributing error of the crash can 

be attributed to the driver of the vehicle in the incorrect lane. To be sure, one can construct 

situations where this would not be the case, but they would be exceptions rather than the rule. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 24

Table 14 

Two-Vehicle Large Truck Crashes by Driver-Related Factors, Truck Type, 

and Vehicle Type 1996-2000

Any Driver-Related Factor

 

Truck type Truck Other Total Truck(%) Other(%) 

 

Combination 2,943 8,896 11,839 25% 75%

Single-unit 1,133 2,869 4,002 28% 72%

Total 4,076 11,765 15,841 26% 74%

Speeding

 

Truck type Truck Other Total Truck(%) Other(%) 

 

Combination 463 1,738 2,201 22% 78%

Single-unit 142 555 697 20% 80%

Total 605 2,293 2,898 22% 78%

Drowsy/Asleep/Inattentive

 

Truck type Truck Other Total Truck(%) Other(%) 

 

Combination 354 1,462 1,816 19% 81%

Single-unit 123 439 562 22% 78%

Total 477 1,901 2,378 20% 80%

Failure to Yield

 

Truck type Truck Other Total Truck(%) Other(%) 

 

Combination 600 2,032 2,632 23% 77%

Single-unit 268 785 1,053 25% 75%

Total 868 2,817 3,685 24% 76%

 Source: NHTSA, NCSA, FARS 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 25

6. ANALYSIS OF TRUCKS IN FATAL ACCIDENTS (TIFA)

The physical evidence of two-vehicle rear-end, sideswipe and head-on crashes combined with the 

relative position of the vehicles suggest that one driver may have contributed to the crash more 

than the other. Drivers of the striking vehicle for rear-end crashes may contribute more to crashes 

than drivers of the struck vehicles. Drivers of sideswipe vehicles that encroached into the lane of 

the other sideswiped vehicle may contribute more to crashes than drivers of vehicles that 

remained in the proper lane. Drivers of vehicles for head-on crashes where the vehicle is in the 

lane of the oncoming vehicle may contribute more to crashes than drivers of vehicles that remain 

in the proper lane. Drivers of vehicles that turn across the path of an oncoming vehicle may 

contribute more to the crash than drivers of the oncoming vehicle, although right-of-way 

considerations can be a complicating factor. The straight path crashes require more information 

than that which is available here to determine which driver contributed most to the crash. The 

data on straight path crashes do not identify right-of-way violations. 

Tables 15a and 15b contain the TIFA fatality crash type data from 1996 to 1999 for two-vehicle 

crashes consisting of one large truck and one passenger vehicle. The first ten data rows of both 

tables consist of five pairs of similar crash types. The highlighted row, within each pair, identifies 

the more prevalent crashes of the pair, that is, the set of crashes with the most fatalities. In general 

this means that the highlighted crashes have more passenger vehicle driver fatalities (columns 2 

and 3), more truck driver fatalities (columns 4 and 5) and more total fatalities (columns 6 and 7). 

For some crash types, there are more than five times the fatalities for the gray highlighted row of 

crashes. The one exception to this rule is combination trucks, specifically truck driver fatalities 

for rear-end crashes; see the heavy boxed area of Table 15a. 

For each pair of rows, the highlighted rows are crashes where the passenger vehicle drivers seem 

to have contributed more to the crash than the driver of the large truck. These results are based on 

the point of impact combined with the relative position of the vehicles, and confirm the results 

based on the driver-related factors. These data suggest that a contributing factor of two-vehicle 

crashes involving a large truck and a passenger vehicle is the poor judgment of the driver of the 

passenger vehicle. For example, there were 1,085 fatalities in two-vehicle crashes involving a 

sideswipe of a large combination truck and another vehicle in which the other vehicle encroached 

into the truck’s lane, but only 58 fatalities involving a sideswipe of a large combination truck and 

another vehicle where the large combination truck encroached into the other vehicles lane. 

With this information available, examine Table 1 again. One sees that 18 percent of fatal crashes 

involving large trucks are single-vehicle crashes; where as 62 percent of fatal non-large truck 

crashes are single-vehicle crashes. This suggests that a problem with some two-vehicle large 

truck crash types may lie with the drivers of the non-large truck vehicles involved in the crash. 

In the case of straight path crashes more information is needed before any determination is made. 

When examining fatal two-vehicle crashes involving a large truck and a passenger vehicle, where 

one vehicle backs into another, ones sees far more fatalities where the large truck driver backed 

into the passenger car, rather than the other way around. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 26

 

Table 15a 

Two-Vehicle Combination Truck Fatalities by Crash Type 1996-1999

Passenger 

Vehicle 

Driver 

Fatalities

Truck 

Driver 

Fatalities 

Total Fatalities 

Crash Type

N (%) N (%) N (%) 

Rear-end, truck striking passenger vehicle 207 3% 25 15% 427 4% 

Rear-end, passenger vehicle striking truck 786 11% 1 1% 1,070 11%

Sideswipe opposite direction, truck encroached 69 1% 6 3 % 101 1% 

Sideswipe opposite direction, passenger vehicle encroached 843 12% 6 3% 1,085 11% 

Sideswipe same direction, truck encroached 21 0 % 9 5% 58 1% 

Sideswipe same direction, passenger vehicle encroached 114 2% 11 6% 193 2% 

Head-on truck in passenger vehicle lane 130 2% 3 2% 177 2% 

Head-on passenger vehicle in truck lane 1,324 19% 14 8% 1,696 17% 

Truck turned across path of passenger vehicle 332 5% 1 1% 465 5% 

Passenger vehicle turned across path of truck 566 8% 10 6% 829 8% 

Other turning related 54 1% 0 0% 87 1% 

Straight path, truck into passenger vehicle 931 13% 20 12% 1,416 14% 

Straight path, passenger vehicle into truck 453 6% 5 3% 634 6% 

Truck backed into passenger vehicle 70 1% 0 0% 87 1% 

Passenger vehicle backed into truck 1 0% 0 0% 2 0% 

Other crash type 821 12% 55 32% 1,337 13% 

Unknown crash type 304 4% 7 4% 428 4% 

Total Combination Trucks 7,026 100 % 173 100% 10,092 100% 

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 27

 Table 15b 

Two-Vehicle Single-unit Truck Fatalities by Crash Type 1996-1999 

Passenger 

Vehicle 

Driver 

Fatalities 

Truck 

Driver 

Fatalities 

Total Fatalities 

Crash Type

N (%) N (%) N (%) 

Rear-end, truck striking passenger vehicle 39 2% 1 2% 60 2% 

Rear-end, passenger vehicle striking truck 269 13% 3 5% 367 12% 

Sideswipe opposite direction, truck encroached 22 1% 1 2% 32 1% 

Sideswipe opposite direction, passenger vehicle encroached 201 9% 2 3% 276 9% 

Sideswipe same direction, truck encroached 3 0% 3 5% 14 0% 

Sideswipe same direction, passenger vehicle encroached 12 1% 3 5% 25 1% 

Head-on truck in passenger vehicle lane 76 4% 2 3% 113 4% 

Head-on passenger vehicle in truck lane 461 22% 4 7% 551 18% 

Truck turned across path of passenger vehicle 90 4% 0 0% 148 5% 

Passenger vehicle turned across path of truck 255 12% 0 0% 334 11% 

Other turning related 13 1% 5 9% 14 1% 

Straight path, truck into passenger vehicle 395 19% 7 12% 595 20% 

Straight path, passenger vehicle into truck 112 5% 12 21% 178 6% 

Truck backed into passenger vehicle 11 0% 0 0% 11 0% 

Passenger vehicle backed into truck 1 0% 1 2% 5 0% 

Other crash type 147 7% 14 24% 259 9% 

Unknown crash type 22 1% 0 0% 32 1% 

Total Single-unit Trucks 2,129 100% 58 100% 3,014 100% 

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 28

More large truck crash fatalities occur in the first hour after a break of at least eight hours than 

during any other hour. In general, as the number of hours increase, after the required break of at 

least eight hours, there are fewer fatal crashes. Note that some columns are for one hour and 

some columns are for multiple hours. The category “12+" collapses data for 12 or more hours. 

Table 16 

Large Truck Fatalities by Truck Type, Fatality Type, and Hours Driven 

Before the Crash 1996-1999

Combination Trucks 

Fatality Type Hours Driven Before the Crash

 

Occupant 1 2 3-4 5-6 7-8 9-10 11 12+ Unknown

Single-vehicle 233 158 207 137 71 28 2 10 587

Multiple-vehicle 2,407 1,649 2,310 1,549 790 352 24 48 5,528

 

Non-Occupant 194 86 163 126 90 22 1 9 457

 

Single-unit Trucks

Fatality Type Hours Driven Before the Crash

 

Occupant 1 2 3-4 5-6 7-8 9-10 11 12+ Unknown

Single-vehicle 86 41 71 29 15 4 1 0 240

Multiple-vehicle 859 328 439 322 199 43 6 10 1,966

 

Non-Occupant 87 34 56 26 12 4 3 0 253

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 29

The distributions of the intended one-way trip distance reflect the difference in travel patterns 

between the two types of large trucks. The entire one-way trip distance is coded even if the trip 

requires multiple days of travel. The known intended one-way trip distance for single-unit truck 

fatalities is concentrated at the local level, that is within a radius of 50 miles, whereas the 

distribution of combination truck fatalities by intended one-way trip distance is much flatter and 

more uniform. 

Table 17 

Fatalities by Trip Distance for Large Truck Crashes by 

Truck Type and Fatality Type 1996-1999

Combination Trucks

Fatality Type Trip Distance (In Miles)

Occupant Local 51-100 101-200 201-500 >500 Unknown

 

Single-vehicle 283 157 160 257 299 277

Multiple-vehicle 3,229 1,842 1,743 2,466 2,762 2,615

 

Non-Occupant 271 126 104 176 204 267

 

Single-unit Trucks

 Fatality Type Trip Distance (In Miles)

 

Occupant Local 51-100 101-200 201-500 >500 Unknown

Single-vehicle 236 58 15 17 6 155

Multiple-vehicle 2,294 344 145 97 36 1,237

 

Non-Occupant 258 31 11 8 4 163

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 30

Over 64 percent of the single-vehicle occupant fatalities occurred in crashes with a rollover, but 

less than 2 percent of the non-occupant fatalities occurred in crashes with a rollover. 

Table 18 

Large Truck Fatalities by Truck Type, 

Fatality Type and Rollover 1996-1999

Combination Trucks

Fatality Type Rollover

 

Occupant No Yes 

Single-vehicle 531 902

Multiple-vehicle 13,427 1,230

Non-Occupant 1,119 29

Single-unit Trucks

Fatality Type Rollover

 

Occupant No Yes 

Single-vehicle 164 323

Multiple-vehicle 3,704 468

Non-Occupant 474 1

Grand Total 

Fatality Type Rollover 

 No Yes 

Single-vehicle 695(36%) 1,225(64%)

Multiple-vehicle 17,131(91%) 1,698(9%)

 Non-Occupant 1,593(98%) 30(2%)

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 31

The mean gross weight is positively associated with rollovers. Combination trucks involved in 

fatal crashes that experience a rollover have trailers with higher gross mean weights than 

combination trucks that do not experience a rollover. A similar result exists for single-unit trucks. 

Namely, single-unit trucks that experience a rollover during a fatal crash have higher mean power 

unit gross weights than those that do not rollover (see Tables 27 and 28 for the effect of weight on 

a large truck’s propensity to rollover in a single-vehicle fatal crash). Contrast this result with 

jackknifes, Tables 24 and 29, where the relationship is in the opposite direction. 

Table 19 

Mean Gross Weight (lbs) of Large Trucks by Truck Type, Crash Type, 

Number of Trailers, and Rollover 1996-1999

Combination Trucks

Crash Type Power Unit 1st Trailer 2nd Trailer 

 Rollover No Rollover Rollover No Rollover Rollover No Rollover

Single-vehicle 

1 Trailer 17,397 16,994 50,551 33,184 N/A N/A 

2 Trailers 14,431 14,982 23,406 23,244 23,578 21,722

 

Multiple-vehicle 

1 Trailer 17,947 17,297 46,938 35,343 N/A N/A 

2 Trailers 15,861 15,766 25,273 23,613 22,216 21,142

 

Single-unit Trucks

Crash Type Power Unit 1st Trailer 2nd Trailer 

 Rollover No Rollover Rollover No Rollover Rollover No Rollover

Single-vehicle 28,341 22,978 

Multiple-vehicle 30,469 25,688 N/A N/A N/A N/A 

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 32

There is no appreciable difference in the length of large trucks involved in fatal crashes 

between single-vehicle crashes and multiple-vehicle crashes. However, the mean length of 

the power unit of combinations trucks with two trailers is approximately 3 feet less than the 

length of the power unit of combination trucks with a single trailer, the overall length of a 

combination truck with two trailers is 9 feet longer. The mean length of each unit of a 

combination truck with 2 trailers is shorter than the mean length of each unit of a combination 

truck with a single trailer, but the overall length is longer. 

Table 20 

 Mean Unit Length of Large Trucks by Truck Type, 

Fatality Type, and Length in Feet 1996-1999

Combination Trucks 

Fatality Type Length in Feet 

 Power Unit 1st Trailer 2nd Trailer 

 

Single-vehicle 

1 Trailer 24.0 44.6 N/A 

2 Trailers 21.0 29.8 27.2

Multiple-vehicle 

1 Trailer 24.3 44.7 N/A 

2 Trailers 21.6 29.5 27.0

Single-unit Trucks 

Fatality Type Length in Feet 

 Power Unit 1st Trailer 2nd Trailer 

 

Single-vehicle 26.8 N/A N/A 

Multiple-vehicle 26.8 N/A N/A 

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 33

Most of the fatalities attributed to crashes involving combination trucks with two trailers have 

trailers of equal length. This pattern is consistent for all fatality types, occupant and non-occupant 

fatalities. 

Table 21 

Combination Truck Fatalities by Fatality Type 

and Relation of Trailer Length 1996-1999

Combination Trucks 

Relation of Trailer Lengths 

Fatality Type 1st < 2nd 1st = 2nd 1st > 2nd

Occupant 

Single-vehicle 1 51 12

Multiple-vehicle 12 466 143

 

Non-Occupant 1 55 14

 Source: NHTSA, NCSA, FARS, TIFA 

 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 34

Approximately 10 percent of combination truck occupant fatalities are associated with a 

jackknife; see Table 22. Over 90 percent of these jackknife fatalities involved a combination 

truck with a single trailer; see Table 23. Only 4 percent of combination truck non-occupant 

fatalities are associated with a jackknife. Of these jackknife fatalities, 83 percent involved a 

combination truck with a single trailer. 

Table 22 

Large Truck Fatalities 1996-1999

Combination Trucks by Jackknife*

 Fatality Type Jackknife 

 

Occupant No Yes 

Single-vehicle 1139 157

Multiple-vehicle 12,138 1,312

Total 13,277(90%) 1,469(10%)

Non-Occupant 968(96%) 36(4%)

 Source: NCSA, NHTSA, FARS, TIFA 

 * Some combination trucks are not articulated, e.g., bobtails. 

 

Table 23 

Combination Truck Fatalities by 

Occupant Type and Number of Trailers 

1996-1999

Combination Truck Jackknife 

Jackknife by Number of Trailers 

 Fatality Type No. of Trailers 

 

Occupant 1 >1 

Single-vehicle 145 12

Multiple-vehicle 1,198 114

Total 1,343(91%) 126(9%)

Non-Occupant 30(83%) 6(17%)

 Source: NCSA, NHTSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 35

The mean total trailer weight, of large combination trucks that experience a jackknife, tends to be 

less than the mean total trailer weight of large combination trucks that do not experience a 

jackknife. This finding suggests that as the total trailer weight decreases, the probability of a 

jackknife increases (see Table 29 for the effect of weight on a large combination truck’s 

propensity to experience a jackknife in a single-vehicle fatal crash). This is confirmed by the 

multivariate analysis; see Table 29. The exception is single-vehicle crashes with one trailer; 

however, the difference in mean trailer weight is less than 150 pounds. This result can be 

contrasted with the relation between weight and rollover. As weight increases, rollovers increase 

and jackknives decrease; see Tables 19, 24, 27, 28 and 29. 

Table 24 

Mean Gross Weight (lbs) of Units for Combination Trucks 

by Type of Crash, Number of Trailers, and Jackknife 1996-1999

 Power Unit 1st Trailer 2nd Trailer 

 No Jackknife Jackknife No Jackknife Jackknife No Jackknife Jackknife

Single-vehicle 

1 Trailer 16,980 17,432 40,709 40,857 N/A N/A 

2 Trailers 14,829 14,616 24,011 20,563 22,864 22,344

 

Multiple-vehicle 

1 Trailer 17,169 16,756 37,501 28,366 N/A N/A 

2 Trailers 15,735 15,471 25,390 16,615 22,586 14,787

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 36

Most occupant fatalities related to large truck sideswipe crashes occur with opposite direction 

sideswipes. Approximately 76 percent of occupant sideswipe-related fatalities involving a 

combination truck are opposite direction sideswipes. For single-unit trucks, the portion is 82 

percent. Non-occupant fatalities involving a sideswipe are quite rare and no conclusions should 

be drawn from the data. 

Table 25 

Large Truck Fatalities by Truck Type, 

Fatality Type, and Sideswipe Direction 

1996-1999

Combination Trucks

Fatality Type Sideswipe

 

Occupant Same 

Direction

Opposite 

Direction 

Multiple-vehicle 727(24%) 2,348(76%)

Non-Occupant 6 4

Single-unit Trucks

Fatality Type Sideswipe

 

Occupant Same 

Direction

Opposite 

Direction 

Multiple-vehicle 114(18%) 516(82%)

Non-Occupant 4 0

 Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 37

7. PROPENSITY TO ROLL OVER/JACKKNIFE 

Rollover and jackknife crashes are complex events influenced by driver characteristics, the 

driving environment, the vehicle, and the interaction among the three. This section investigates 

the effects of the driving environment and the vehicle on a large truck’s propensity to roll over or 

jackknife in a single-vehicle fatal crash. 

The National Highway Traffic Safety Administration (NHTSA) has developed a five-star rating 

system to inform consumers about the rollover resistance of passenger cars, light multipurpose 

passenger vehicles, and trucks. The ratings are derived from the relationship between measured 

values of the static stability factor (SSF) and corresponding rollover rates determined from singlevehicle crash data. SSF is defined as the vehicle’s track width, T, divided by twice its center of 

gravity height, H; i.e., SSF=T/2H. For large trucks, the height of an unloaded vehicle with a 

driver as the only occupant is used in this calculation. However, the actual center of gravity does 

fluctuate with the load. Therefore, instead of using the SSF, the weight (including the cargo 

weight) and the dimensions of the truck are used in the analysis. Single large truck fatal crashes 

served as the exposure measure for assessing the relative magnitude of the rollover (jackknife) 

problem, i.e., number of rollover (jackknife) events / number of single-large-truck fatal crashes. 

The crashes included in the analysis are single-vehicle fatal crashes for large trucks in TIFA 

between 1996 and 1999. 

The binary response model, for rollovers (jackknifes), states that the probability of a rollover 

(jackknife), given that a single-truck fatal crash has occurred, is a function of selected explanatory 

variables. If Y denotes the dependent variable in a binary-response model for rollovers 

(jackknifes), Y is equal to 1 if there is a rollover (jackknife) and 0 otherwise. The statistical 

problem is to estimate the probability that Y=1, considered as a function of the explanatory 

variables. TIFA data are analyzed using a logit model, which is a widely used binary-response 

model. The logit model is as follows: 

 Pr(Y=1| X= x) = 1/ [1+exp(α + β x)]. 

Taking the natural logarithm of both sides, this model can be written as 

 ln(P / (1-P)) = α + β x 

where P/ (1-P) is the odds ratio. TIFA is a stratified random sample of large truck fatal crashes. 

Therefore, the RLOGIST procedure in the SUDAAN software is used to estimate the parameters 

in the logit model. All single-vehicle crashes within the TIFA survey were used in this analysis. 

The explanatory variables used in the models are WEATHER, LIGHT, SPLIMIT, CURVE, 

WEIGHT, LENGTH, and WIDTH; see Table 26. An analysis of the parameters of the model 

showed that the variable WIDTH is not significant in predicting rollovers of large trucks. 

Multiple-vehicle crashes are far more complex than single-vehicle crashes. Unfortunately, the 

additional necessary variables to analyze rollovers and jackknifes in multiple-vehicle crashes are 

not available, hence the analysis is limited to single-vehicle crashes. Table 27 and Table 28 give 

results obtained for single-unit trucks and combination trucks, respectively, for single-vehicle 

fatal crashes. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 38

Table 26 

Variables Used for Inclusion in 

Rollover and Jackknife Rate Models 

VARIABLE DEFINITION 

ROLLOVER ROLLOVER = 1 if single-truck fatal crash involved a rollover; 

ROLLOVER = 0 otherwise. 

SPLIMIT Posted speed limit in Miles Per Hour. 

CURVE CURVE = 2 if roadway alignment is curved; Curve = 1 otherwise. 

WEATHER WEATHER = 1 if no adverse atmospheric condition; WEATHER = 2 

otherwise. 

LIGHT LIGHT = 1 if daylight or dark but lighted; LIGHT = 2 otherwise. 

WEIGHT Total weight of the truck (including the cargo weight) in pounds. 

LENGTH Length of the truck in feet 

WIDTH Width of the truck in inches. 

Source: NHTSA, NCSA, FARS, TIFA 

In a single-vehicle fatal crash, the odds of a rollover on a curved road are approximately six times 

the odds of a rollover on a straight road for both single-unit trucks and combination trucks. The 

odds of a rollover for a single-unit truck during adverse weather conditions are three times the 

odds of a rollover in good weather. However, the odds of a rollover, for combination trucks, are 

37 percent higher during adverse weather conditions than in good weather. 

Poor lighting conditions are associated with a 12 percent increase in the predicted odds of a 

rollover for combination trucks, whereas the odds of a rollover decline by 40 percent for singleunit trucks. A 10 mph increase in the posted speed limit contributes to a 172 percent = 

(exp(10x0.1)) increase in the odds of a rollover for single-unit trucks and a 49 percent = 

(exp(10x0.04)) increase in the odds of a rollover for combination trucks. An increase of 10 

percent in cargo weight increases the odds of a rollover by 10 percent = (exp(1.03*ln(1.1))) and 

23 percent = (exp(2.18*ln(1.1))) for single-unit trucks and combination trucks, respectively. On 

the other hand, an increase of 10 percent in length of a truck reduces the odds of a rollover by 10 

percent = (exp(-1.16*ln(1.1))) and 21 percent = (exp(-2.42*ln(1.1))) for single-unit trucks and 

combination trucks, respectively. This may be due to the fact that a truck’s physical center of 

gravity height increases as the cargo weight increases, and decreases as the length of the truck 

increases. These results are consistent with Table 19. 

In the multivariate analysis of fatal passenger vehicle crashes, one often sees that bad weather 

decreases the propensity of a rollover. In the case of large truck fatal crashes, the opposite is true: 

bad weather increases the propensity of rollover. One hypothesis to explain this difference is that 

during bad weather, the less experienced drivers of the passenger vehicle may reduce their travel 

speed more than professional large truck drivers. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 39

Table 27 

Rollover Propensity of Single-unit Trucks 

Multivariate Analysis-Logit Model Results 1996-1999

EFFECTS BETA 

COEFF. 

ODDS 

RATIO 

SE BETA T-TEST P-VALUE 

INTERCEPT -12.2 0.0 1.06 -11.49 < 0.0001 

SPLIMIT 0.10 1.10 0.00 22.23 < 0.0001 

CURVE 1.78 5.91 0.15 11.61 < 0.0001 

WEATHER 1.10 3.00 0.23 4.68 <0.0001 

LIGHT -0.51 0.60 0.16 -3.22 0.0013 

ln(WEIGHT) 1.03 2.80 0.10 10.12 < 0.0001 

ln(LENGTH) -1.16 0.31 0.37 -3.18 0.0015 

Source: NHTSA, NCSA, FARS, TIFA 

Table 28 

Rollover Propensity of Combination Trucks 

Multivariate Analysis-Logit Model Results 1996-1999

EFFECTS BETA 

COEFF. 

ODDS 

RATIO 

SE BETA T-TEST P-VALUE 

INTERCEPT -16.64 0.0 0.88 -18.95 < 0.0001 

SPLIMIT 0.04 1.04 0.00 14.20 < 0.0001 

CURVE 1.80 6.03 0.07 27.61 < 0.0001 

WEATHER 0.31 1.37 0.08 3.96 <0.0001 

LIGHT 0.11 1.12 0.06 1.95 0.0516 

ln(WEIGHT) 2.18 8.80 0.07 31.41 < 0.0001 

ln(LENGTH) -2.42 0.09 0.18 -13.34 < 0.0001 

Source: NHTSA, NCSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 40

We now investigate the effects of the factors listed in Table 26 on the propensity of a large 

combination truck jackknife, in a single-vehicle fatal crash. 

The binary response model for a jackknife indicates that the probability of a jackknife, given that a 

fatal crash involving a single combination truck has occurred, is a function of the selected explanatory 

variables. If Y denotes the dependent variable in a binary-response model for jackknifes, Y is equal 

to 1 if there is a jackknife and 0 otherwise. The logit model estimates the probability that Y=1, 

considered as a function of the explanatory variables. Table 29 gives results obtained for combination 

trucks involved in single-vehicle crashes. 

In a single-vehicle fatal crash, the odds of a jackknife are 3.22 times higher during adverse weather 

conditions. The odds of a jackknife on a curved roadway are 86 percent higher than the odds of a 

jackknife on a straight roadway. Poor lighting conditions increase the odds of a jackknife by 43 

percent. A 10 mph increase in the posted speed limit increases the odds of a jackknife by 49 percent 

(exp(10x0.04)) for combination trucks. An increase of 10 percent in the total weight of the truck 

corresponds to a 2 percent (exp(-0.23*ln(1.1))) decline in the odds of a jackknife. Whereas a 10 

percent increase in the total length of the truck corresponds to an increase of 14 percent 

(exp(1.33*ln(1.1))) in the odds of a jackknife for combination trucks (these results are also consistent 

with Table 24). Thus, one sees that as the number of trailing units increase, the total length of the 

truck increases, and the propensity for a jackknife increases. 

Table 29 

Jackknife Propensity of Combination Trucks 

Multivariate Analysis-Logit Model Results 1996-1999

EFFECTS BETA 

COEFF. 

ODDS 

RATIO 

SE BETA T-TEST P-VALUE 

INTERCEPT -8.27 0.0 1.43 -5.78 < 0.0001 

SPLIMIT 0.04 1.04 0.00 8.54 < 0.0001 

CURVE 0.62 1.86 0.08 8.19 < 0.0001 

WEATHER 1.17 3.22 0.09 13.55 <0.0001 

LIGHT 0.36 1.43 0.07 4.85 <0.0001 

ln(WEIGHT) -0.23 0.80 0.10 -2.21 0.0271 

ln(LENGTH) 1.33 3.79 0.43 3.11 0.0019 

Source: NCSA, NHTSA, FARS, TIFA 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 41

8. CONCLUSIONS 

No significant clusters of large truck crashes became apparent during the analysis. However, we 

have been able to extract a great deal of interesting characteristics of large truck crashes contained in 

the agency’s large fatal crash files. More detailed information is required, much of which is currently 

being collected for the Large Truck Crash Causation Study. We have been able to extract the 

following conclusions: 

• Just over half of all large truck fatalities occur on non-divided 2-lane roadways. Clearly, 

the large truck fatal crash problem is neither on interstates, nor on major roadways; it is on 

non-divided 2-lane roads. 

• When the geometry of fatal crashes is analyzed, one sees that the relative positions of the 

vehicles, just prior to the crash, can be a contributing factor to the crash. For example, 

using all fatalities as an outcome measure, approximately 10 times as many fatalities result 

in sideswipe opposite direction crashes where the passenger vehicle encroached into the 

truck’s lane, compared to sideswipe opposite direction crashes where the truck encroached 

into the passenger vehicle’s lane. This might suggest that the drivers of the passenger 

vehicles are somewhat more reckless or over confident than the large truck drivers. 

• A speed limit of 55 mph or higher, poor weather, and a curved road significantly increase the 

odds of both a rollover and a jackknife for large trucks. As the weight of the large truck and 

its cargo increases, the odds of a rollover increase, but the odds of a jackknife decrease. 

Conversely, as the length of a large truck increases, the odds of a rollover decrease, while the 

odds of a jackknife increase. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 42
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 43

9. REFERENCES 

Blower, D., The Relative Contribution of Truck Drivers and Passenger Vehicle Drivers to TruckPassenger Vehicle Traffic Crashes Center for National Truck Statistics, The University of 

Michigan Transportation Research Institute, UMTRI 98-25, June 1998. 

Blower, D. and Pettis, L., Trucks Involved in Fatal Accidents Codebook 1994 Center for National 

Truck Statistics, The University of Michigan Transportation Research Institute, UMTRI-96-24, 

1996. 

Blower, D. and Pettis, L., Trucks Involved in Fatal Accidents Codebook 1995 Center for National 

Truck Statistics, The University of Michigan Transportation Research Institute, UMTRI-97-10, 

1997. 

Blower, D. and Pettis, L., Trucks Involved in Fatal Accidents Codebook 1996 Center for National 

Truck Statistics, The University of Michigan Transportation Research Institute, UMTRI-98-14, 

1998. 

Blower, D., Masters, R., Pettis, L., Trucks Involved in Fatal Accidents Codebook 1997 Center for 

National Truck Statistics, The University of Michigan Transportation Research Institute, UMTRI99-18, 1999. 

Highway Statistics 97, FHW -PL-98-020, HPM-40/10-98(4M)P, November 1998. 

Tessmer, J.M., FARS Analytic Reference Guide 1975-2002, DOT HS 808 792, U.S. Department 

of Transportation, Washington D.C., 2002. 

Traffic Safety Facts 1994, National Highway Traffic Safety Administration, National Center for 

Statistics and Analysis, 1995. 

Traffic Safety Facts 1995, National Highway Traffic Safety Administration, National Center for 

Statistics and Analysis, 1996. 

Traffic Safety Facts 1996, National Highway Traffic Safety Administration, National Center for 

Statistics and Analysis, 1997. 

Traffic Safety Facts 1997, National Highway Traffic Safety Administration, National Center for 

Statistics and Analysis, DOT HS 808 766, 1998. 

Traffic Safety Facts 1998, National Highway Traffic Safety Administration, National Center for 

Statistics and Analysis, DOT HS 808 983, 1999. 

Traffic Safety Facts 1999, National Highway Traffic Safety Administration, National Center for 

Statistics and Analysis, DOT HS 809 100, 2000. 
 National Center for Statistics and Analysis ♦ 400 Seventh St., S.W., Washington, D.C. 20590 44

Traffic Safety Facts 2000, National Highway Traffic Safety Administration, National Center for 

Statistics and Analysis, DOT HS 809 337, 2001.