U.S. Department 

of Transportation 

National Highway 

Traffic Safety 

Administration 

DOT HS 809 676 November 2003 

Technical Report 

The Relationship between Occupant 

Compartment Deformation and 

Occupant Injury 

Published By: 

National Center for Statistics and Analysis 

Research and Development
 National Center for Statistics and Analysis, 400 Seventh St., S.W., Washington, DC 20590 1

This publication is distributed by the U.S. Department of Transportation, National 

Highway Traffic Safety Administration, in the interest of information exchange. The 

opinions, findings and conclusions expressed in this publication are those of the author(s) 

and not necessarily those of the Department of Transportation or the National Highway 

Traffic Safety Administration. The United States Government assumes no liability for its 

contents or use thereof. If trade or manufacturers’ names are mentioned, it is only 

because they are considered essential to the object of the publication and should not be 

construed as an endorsement. The United States Government does not endorse products 

or manufacturers. 
Technical Report Documentation Page

1. Report No. 

DOT HS 809 676

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

5. Report Date 

November 2003 

4. Title and Subtitle 

The Relationship between Occupant Compartment Deformation 

and Occupant Injury 6. Performing Organization Code 

NPO - 121 

7. Author(s) 

Eigen, Ana María; Glassbrenner, Donna 

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 

NPO-121, 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 

NPO-121, 400 Seventh Street, S.W. 

Washington, D.C. 20590

14. Sponsoring Agency Code 

15. Supplementary Notes 

The authors wish to acknowledge the invaluable collaboration of John Hinch, Susan Partyka, and Randa Samaha for their 

problem identification, insight into problem development, and advisory role throughout the elaboration of this project. 

Abstract 

In collaboration with and at the request of the Federal Highway Administration (FHWA), this report examines the relationship 

between occupant compartment deformation and injury to the occupant. An evaluation criterion for roadside safety hardware 

is the extent of deformation and the accompanying intrusion into the occupant compartment. This is particularly an issue with 

pickup trucks in impacts with longitudinal barriers. For impacts with longitudinal barriers, deformation and intrusion are 

typically in the wheel well and floor pan areas. The FHWA has set a guideline of 15 cm (6 in.) as the pass/fail point providing 

the only quantitative threshold available for testing. Unfortunately, there is no established relationship between occupant 

compartment deformation and intrusion and injury severity. Thus, it is difficult to assess the guidelines set forth by FHWA. 

The subsequent work seeks to address this topic via data evaluation and statistical analyses. 

In this report, The National Automotive Sampling System – Crashworthiness Data System was used to examine intrusion 

magnitude thresholds and their associated injury severities. Significance testing on the intrusion-injury relationship was 

performed for a variety of objects contacted and intruding components. It was found that lower limb injuries were the most 

prevalent for the toe pan, forward of the A-pillar, and floor pan intrusions. Additionally, the risk of moderate injury severity 

and greater increases as the intrusion magnitude increases. 

17. Key Words 

occupant compartment deformation, passenger vehicles, 

toe pan, forward of A-pillar, and floor pan deformations, 

guardrails, bridge rails, roadside hardware 

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 

37 

22. Price 

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

TABLE OF CONTENTS 

1. Executive Summary........................................................... 1

2. Introduction....................................................................... 2

Summary..................................................................................................................................... 2 

Conclusions................................................................................................................................. 3 

3. Database Selection Rationale............................................ 4

4. CDS Definitions................................................................. 5

Unique Crash Identifiers............................................................................................................. 5 

Object Contacted Associated with the Highest Severity ............................................................ 5 

Intruded Component ................................................................................................................... 5 

Intrusion Magnitude.................................................................................................................... 5 

Intrusion Area ............................................................................................................................. 6 

Seating Position .......................................................................................................................... 6 

Age.............................................................................................................................................. 6 

Injury Severity ............................................................................................................................ 6 

Body Region ............................................................................................................................... 7 

5. Cases Selected from CDS .................................................. 8

Methodology............................................................................................................................... 8 

Years of Study............................................................................................................................. 8 

Relevant Vehicle Selection......................................................................................................... 8 

Occupant Demography ............................................................................................................... 9 

Resultant Injury Dataset Merge Caveats................................................................................... 10 

Methodological Adjustments based Upon Limitations............................................................. 10 

6. Results.............................................................................. 13

7. Significance Tests............................................................ 14

Background............................................................................................................................... 14 

Struck Object Categorization for Significance Testing ............................................................ 14 

Component Categorization for Significance Testing................................................................ 14 

Intrusion Categorization for Significance Testing.................................................................... 14 

Injury Categorization for Significance Testing......................................................................... 14 

Relationship between Intrusion and Injury Scenarios .............................................................. 14 

Sample Output .......................................................................................................................... 15 

8. Analysis of Moderate to Maximum Injuries................... 19

Results by Intruding Component .............................................................................................. 21 

9. Summary of Results......................................................... 24

Vehicle Striking Vehicle........................................................................................................... 24 

Fixed Object Struck .................................................................................................................. 24 

10. Recommendations for Future Study ............................... 25

Examine Several More Years of NASS - CDS......................................................................... 25 

Expand Search by Generalizing Scope to Include GES ........................................................... 25 
 ii

Work with Anecdotal Data ....................................................................................................... 25 

Control for Vehicle Body Types............................................................................................... 25

Examine All Toe Pan, Floor Pan, or Forward of the A-Pillar Cases........................................ 26 

11. Appendix.......................................................................... 27

A. Data Sets ........................................................................................................................... 27 

B. Selected CDS Definitions ................................................................................................. 29 

C. Number of Nearside Occupant, Age 13 Years and Older, Injuries that were Associated 

with a Relevant Intrusion.......................................................................................................... 33 

D. Relevant Intrusions Resulting from Impact with Other Vehicle ...................................... 36 

E. Relevant crashes.................................................................................................................. 37 

12. References ....................................................................... 38
 iii

List of Tables and Figures 

Table 1: Intrusion Magnitude as reported in NASS - CDS....................................................................6

Table 2: Abbreviated Injury Scale Definitions and Lower Extremity Injury Examples.....................7

Table 3: Number of Vehicles with Nearside Occupant Intrusion Pursuant to a Guardrail Impact, 

by Intrusion Magnitude (Sample size given in parenthesis.) .............................................................11

Table 4: Number of Vehicles with Nearside Occupant Intrusion Pursuant to a Toe Pan, Floor Pan, 

or Forward of the A-Pillar Intrusion, by Object Contacted and Intrusion Magnitude.............12

(Sample size given in parenthesis.) ..........................................................................................................12

Table 5: Frequency of Levels of Nearside Occupant Injury at Two Intrusion Levels for Intrusion 

into Toe Pan, Floor Pan, or Forward of the A-Pillar ....................................................................15

by a Fixed Object.......................................................................................................................................15

Figure 1: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by Other 

Vehicle with Toe Pan, Forward of A-Pillar, and/or Floor Pan Intrusions ..................................16

Figure 2: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by Other 

Vehicle with Toe Pan Intrusion.......................................................................................................17

Figure 3: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by NonVehicle with Toe Pan, Forward of A-Pillar, and Floor Pan Intrusion.........................................17

Figure 4: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by NonVehicle with Toe Pan Intrusion.......................................................................................................18

Table 6: P-values of the Significant Intrusion-Nearside Occupant Injury Relationships .................18

for Toe Pan, Floor Pan, or Forward of the A-Pillar..............................................................................18

Table 7: AIS 2+ Nearside Occupant Injuries by Object Contacted, Intruding Component.............19

Table 8: AIS 3+ Nearside Occupant Injuries by Object Contacted, Intruding Component.............20

and Injured Body Region .........................................................................................................................20

Figure 5: Distribution of AIS 2+ Nearside Occupant Injuries from Toe Pan, Floor Pan, and 

Forward of the A-Pillar Intrusion for Vehicles Striking a Fixed Object ....................................20

Figure 6: Distribution of AIS 3+ Nearside Occupant Injuries from Toe Pan, Floor Pan, and 

Forward of the A-Pillar Intrusion for Vehicles Striking a Fixed Object ....................................21

Figure 7: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 2 in 

Vehicles with Toe Pan Striking Vehicle..........................................................................................22

Figure 8: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 2 in 

Vehicles with Toe Pan, Forward of A-Pillar, and/or Floor Pan Intrusion Striking Non-Vehicle

............................................................................................................................................................22

Figure 9: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 3 in 

Vehicles with Toe Pan Striking Vehicle..........................................................................................23

Figure 10: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 3 in 

Vehicles with Toe Pan, Forward of A-Pillar, and/or Floor Pan Intrusion Striking Non-Vehicle

............................................................................................................................................................23

Table 9: Intrusion into Occupant Compartment by Intruding Component, AIS 1 ...........................33

Table 10: Intrusion into Occupant Compartment by Intruding Component, AIS 2.........................34

Table 11: Intrusion into Occupant Compartment by Intruding Component, AIS 3.........................35

Table 12: Intrusion into Occupant Compartment by Intruding Component, AIS 4.........................35

Table 13: Relative Frequency of Bifurcated Nearside Occupant Injury Levels Occurring at 

Bifurcated Intrusion Levels in Crashes with Impacts with Other Vehicles Inducing Toe Pan, 

Floor Pan, and/or Forward of the A-Pillar Damage......................................................................36

Table 14: Relative Frequency of Bifurcated Nearside Occupant Injury Levels Occurring at 

Bifurcated Intrusion Levels in Crashes with Impacts with Non-Vehicles (Fixed Objects) 

Inducing Toe Pan, Floor Pan, and/or Forward of the A-Pillar Damage .....................................37
1. Executive Summary 

This report is presented in response to a request from and in collaboration with the Federal 

Highway Administration (FHWA). In an effort to reduce the severity of single vehicle run-offthe-road crashes, the FHWA requires that all roadside features installed on the National Highway 

System be crashworthy, a determination based on satisfactory performance of the device under 

specified impact conditions. The specific tests that must be run and the evaluation criteria to be 

met for each category of roadside hardware are defined in the National Cooperative Highway 

Research Program (NCHRP) Report 350, “Recommended Procedures for the Safety 

Performance Evaluation of Highway Features.” This report sets forth many guidelines for 

systematically evaluating the safety performance of roadside hardware, one of which is the 

degree of intrusion into the occupant compartment of the vehicle used to test the device. 

Unfortunately, the current guidelines on allowable intrusion are very subjective and have lead to 

inconsistent conclusions regarding the acceptability of many types of roadside hardware. 

National Highway Traffic Safety Administration’s (NHTSA) National Center for Statistics and 

Analysis (NCSA) has conducted an analysis using NASS-CDS data to evaluate the relationship 

between occupant compartment intrusion and occupant injury. FHWA and the roadside safety 

community can use these relationships to evaluate acceptable thresholds of intrusion resulting 

from crash tests. It should be noted that if a piece of guardrail or any other type of external 

roadside feature intrudes into the passenger compartment, the result is failure of the prescribed 

test. Finally, the information contained in this report may be incorporated into the revision to 

NCHRP Report 350 that is now underway. 
 2

2. Introduction 

There are many types of roadside hardware located along the edge of the nation’s highway 

system. These items included guardrails and bridge rails, sign and luminaire supports, and crash 

cushions, to name a few. These systems are designed to reduce the severity of a crash or to 

shield a motorist from a more hazardous object or feature. The role of selecting appropriate 

devices typically lies with the individual State Departments of Transportation. The States often 

work together, sponsoring research to develop safe systems and installation methodologies, and 

methods to evaluate the performance of new roadside safety systems. The definitive guidelines 

for evaluating roadside systems are contained in the National Cooperative Highway Research 

Program (NCHRP) Report 350, “Recommended Procedures for the Safety Performance 

Evaluation of Highway Features.” This methodology was developed based on the needs 

identified by chief administrators of the highway and transportation departments, by committees 

of American Association of State Highway and Transportation Officials (AASHTO), and the 

Federal Highway Administration (FHWA). The FHWA requires that all roadside features 

installed on the National Highway System meet the evaluation criteria contained in Report 350. 

Although most of the evaluation criteria recommended in NCHRP Report 350 are specific and 

unambiguous, some are highly subjective. In particular, Chapter 5 of NCHRP Report 350, Table 

5.1, evaluation criteria “D,” states, in part, “Deformations of, or intrusions into, the occupant 

compartment that could cause serious injuries should not be permitted.” The location and extent 

of occupant compartment intrusion that might cause “serious injury” is not quantified, nor is a 

definition of “serious injury” offered. There are no uniform guidelines that a researcher or 

highway agency can use to assess whether deformation or intrusion resulting from crash damage 

will result in serious injury. To provide some degree of uniformity among the various testing 

agencies, FHWA has arbitrarily set 15 cm deformation of the occupant compartment as the 

threshold beyond which serious injury may result. This determination does not specifically 

address the location of the deformation or the size of the vehicle involved in the crash. 

The highway safety community is in the process of updating NCHRP Report 350 (Powers, 

2003), and is interested in quantifying the current deformation and intrusion evaluation criteria. 

For this reason, the National Center for Statistics and Analysis (NCSA) has worked in 

conjunction with FHWA to undertake this study. The results of this study can be directly 

applicable to that goal. 

Summary 

The study seeks to: 

• Examine the 15 centimeter floor pan/wheel well intrusion guideline used to evaluate 

roadside safety and occupant injury. 

NCSA undertook an examination of the National Automotive Sampling System (NASS) – 

Crashworthiness Data System (CDS) to review real world crash experience in response to a 

request from the FHWA. Passenger vehicles with damage to the toe pan, forward of the A-pillar, 

and floor pan were isolated for analysis, without regard to the object struck, as surrogates for 

occupant compartment deformation induced by longitudinal roadside hardware intrusion. 
 3

Crashes in which a vehicle contacted another vehicle were also examined because of the sample 

size issues. 

Conclusions listed below were based on analysis of the following NASS – CDS variables: 

Vehicle Type: Passenger vehicles (passenger cars and light trucks). 

Occupant Ages: Greater than or equal to 13 years old. 

Seating Positions: Driver and front right passenger seat. 

Intruding Component: Toe pan, forward of the A-pillar, and floor pan. These are 

referenced throughout this report as relevant intrusion. In CDS, forward of the A-pillar 

and front side panel are used to describe the attribute of interest, therefore, these are used 

interchangeably in the text. 

Relevant Crashes: Crashes in which the case vehicle strikes a fixed (non-vehicle) object 

resulting in toe pan, forward of the A-pillar, or floor pan intrusion. 

Intrusion: Occupant compartment deformation induced by relevant intrusion. 

Injury Severity: Abbreviated Injury Scale (AIS) ranging from AIS 1, minor, through 

AIS 6, maximum (untreatable). 

Object Contacted: No limitation. Selected Intruding Components acted as roadside

hardware object struck surrogate. 

Years: Crashes occurring during the years 1991 – 2000 and recorded in NASS - CDS. 

Conclusions 

Based on Chi-Square tests, the data indicates that many moderate to maximum injuries occur at 

intrusions into the occupant compartment that are less deep than the 15 centimeter threshold set 

forth by the FHWA. Sample size issues preclude a more detailed analysis and obviate 

controlling for other factors, such as belt use, age of vehicle occupant, or vehicle body type. The 

analysis is also based on an aggregation of fixed objects that may exhibit different deformation 

characteristics, which upon aggregation disappear. Finally, these results are based upon an 

assessment of life-impairment, consistent with lower limb injuries, rather than risk of mortality; 

however, impairment and mortality are addressed when interpreting the results. 
 4

3. Database Selection Rationale 

A comprehensive crash report was required for this study. An integrated examination of the 

vehicle, roadway environment, and occupant demography was necessary to address the possible 

improvement to the current guardrail intrusion guideline. NCSA compiles and maintains two 

databases under the aegis of NASS. NASS - General Estimates System (GES) is a representative 

sample of crashes occurring in the United States. The NASS - CDS is a nationally representative 

database concentrating on crashes of greatest concern to the highway safety community and the 

public. 

GES and CDS are based on the police accident report (PAR). GES, however, relies only on the 

police officer’s interpretation of the event. A NASS researcher does not examine the vehicle or 

interview occupants. For these reasons, a more subjective and less detailed account is compiled. 

This is not conducive to addressing questions specific to crashworthiness performance of 

roadside hardware. Additionally, the question of injury severity is assessed on a non-medical 

scale (KABCO), whose score is assigned by the law enforcement official on the scene. 

The NASS – CDS is a comprehensive description of approximately 4,500 nationally 

representative crash events each year. This data set is based on the PAR only in so far as the 

selection criteria. Upon selection, the work of the investigation staff begins. The comprehensive 

crash scene and vehicle review combines with the occupant demography and injury accounts. 

The CDS was chosen owing to its: thorough tow-away vehicle inspection, inclusive injuryspecific data for occupants of towed vehicle, and multi-variable link of occupant injury to 

vehicle damage. By examining the complete crash file, the study can encompass the most 

general crash environment components to the most specific occupant injury attributes via the 

continuity of the year, primary sampling unit (PSU, a geographical area dictated by the sample 

design), case identification number, occupant number, and injury number. An additional 

refinement which links the occupant to the injury occurs with the intrusion area, that is 

equivalent to the seating position, and the intrusion number, that links to the injury record. 

CDS was chosen for this analysis for several reasons. The weightiest was the thorough vehicle 

inspection undertaken by NASS researcher. Further, deformations into the occupant 

compartment are defined and linked to occupant injury and injury severity. GES, although a 

superior research tool, did not meet the needs of this study. By providing, substantial data on 

general transportation safety trends, its strength and one of its purposes, it sacrifices the ability to 

provide an in-depth study of the crash, the strength of CDS and one of its purposes. In this 

regard, both were designed to perform different functions. For the sake of uniformity of the data 

set compiled for this study, the entire analysis contained in this paper was performed using the 

CDS data. 
 5

4. CDS Definitions 

Several variables unique to CDS are included and adapted for this study. Their definitions and 

contribution to the study are outlined in this section. 

Unique Crash Identifiers 

Each crash in CDS is uniquely identified by three elements: year, primary sampling unit (PSU), 

and case identification (caseid) number. The year in which the crash occurs is reported by the 

year variable. The PSU is a geographical subdivision inherent to the sampling plan of the CDS. 

The caseid is a combination of the case number assigned to the crash and the stratum. The 

stratum is a classification based on the sampling plan generated by the Automated Case Selection 

System. Additional elements exist to link vehicles, occupants, and injuries to the appropriate 

crash. A unique vehicle number (vehno) is assigned to each vehicle in a crash. Further, 

occupants are linked to a vehicle, uniquely numbered, and assigned to a seat within the vehicle. 

Each occupant sustaining injuries has a numbered listing of injuries, which can be associated 

with the injury source, body region, and injury severity. 

Object Contacted Associated with the Highest Severity 

The objects contacted retained were those with impacts occurring at the highest delta-v. Delta-v 

is the change in velocity experienced by the case vehicle during an impact and used as a severity 

measure in planar crashes. In general, these objects were categorized as vehicle and non-vehicle. 

Vehicle identifies any multi-vehicular crashes whose most severe crash is attributable to contact 

with another vehicle. Non-vehicle contacts are those impacts with manmade and naturally 

occurring roadside hardware. 

Intruded Component 

The intruding object is said to reduce the occupant space for a specified vehicle sector. In 

response to the guardrail surrogate definition, toe pan, forward of the A-pillar, and floor pan 

were selected. The toe pan is defined as the front portion of the floor that angles up to meet the 

dash panel. The side panel forward of the A1/A2 pillar refers to the interior panel located on the 

side of the vehicle and forward of the front doors. This includes areas directly below the 

instrument panel sometimes referred to as a “kick panel.” Finally, the floor pan, including the 

sill, refers to the floor of the vehicle. This includes the lower portion of the passenger 

compartment. Damage to the three components was used to represent damage from collisions 

with guardrails. 

Intrusion Magnitude 

The intrusion magnitude is defined by a categorical variable that establishes ranges of values for 

intrusion induced by impact. These range from three centimeters through 61 centimeters or 

greater of recorded intrusion. Those cases defined as 61 centimeters and greater are quantifiable 

events measured by the NASS researcher. For this reason, these cases are retained. The 

unquantifiable events are grouped owing to the high severity and rarity of occurrence. The term 

catastrophic is reserved for deformations with severity beyond codification. An unknown 

category exists to indicate intrusions of unspecified magnitude. For purposes of statistical 
 6

analysis, the catastrophic and unknown cases were eventually excluded. These cases were not 

assigned numeric values by which to assess the deformation because the damage was considered 

immeasurable or the vehicle may no longer have been available for measurement by the 

researcher. It should also be noted, as stated above, these represent ranges and not the precise 

values allowing for larger cell sizes when performing analysis. Please reference Table 1. 

Table 1: Intrusion Magnitude as reported in NASS - CDS 

CDS Code Intrusion Magnitude Ranges 

1 3 through 7 centimeters 

2 8 through 14 centimeters 

3 15 through 29 centimeters 

4 30 through 45 centimeters 

5 46 through 60 centimeters 

6 61 centimeters or greater 

7 Catastrophic 

.U Unknown 

Source: NCSA, NHTSA, NASS – CDS, 1991 - 2000 

Intrusion Area 

This area is defined by occupied row and position affected by the intrusion. The definitions 

correspond to those set forth by the seating position described below. 

Seating Position 

Seating positions adjacent to the selected intruded components were retained for this study. 

These were the front left (driver) and the front right (passenger) seats. Rear and center seating 

positions were omitted owing to their lack of proximity to the intruding components. 

Age 

The age variable is reported in one-year increments from zero (less than one year old) through 96 

years old. Ages of 97 years and greater are subsumed within a single code. Owing to their rare 

occurrence, this does not misstate the analysis. The exclusion of those children less than 13 

years old was deemed necessary owing to their developing state. This issue is discussed more 

precisely in subsequent sections. 

Injury Severity 

The CDS offers injury classification on two scales. The first is the KABCO scale, which is a 

visual classification based on a police officer’s observation and reported on the PAR. The 

ranking is in descending order with: killed (K), incapacitating injury (A), non-incapacitating 

injury (B), possible injury (C), and no injury (O). The Abbreviated Injury Scale (AIS), the 

second scale, is a medically assessed classification of injuries based on hospital records. 

Occupants with multiple injuries receive a rating for each injury. This ranking measures threat to 

life induced by injuries sustained over six levels. For completeness, “unknown” and “not 

collected” categories exist. A variant of this is the MAIS that shares the ranking, however, 

reports the level of maximum injury severity. The absence of an injury is understood to be 

defined by an AIS 0 rating, however, this is not recorded in CDS. MAIS 0, however, exists to 

describe those occupants who do not sustain injury. It has been noted in the CDS that occupants 

with injuries of severity less than 6 have expired. It should also be noted that AIS 6 injuries 
 7

generally result in fatality; however, CDS uses a treatment variable to assess the outcome of an 

occupant. To put these rating into a physiological context Table 2 offers an example of injuries 

to the body regions most frequently injured in relevant crashes. These examples are also meant 

to accentuate the life threatening nature of these injuries predicated on the increasing risk of 

fatality as one ascends the AIS scale. It should be noted, however, that life threatening injuries 

to the lower limb are extremely rare. For this reason, the AIS 6 example may seem somewhat 

generic. Table 2 suggests the life devastating rather than life threatening nature of lower 

extremity injuries. 

Table 2: Abbreviated Injury Scale Definitions and Lower Extremity Injury Examples 

AIS 

Code 

Injury 

Severity 

Description 

Lower Extremity Example of Injury by AIS Level 

0 Uninjured No body region listed in absence of an injury. 

1 Minor Ankle Sprain 

2 Moderate Hip Dislocation 

3 Serious Femur Fracture 

4 Severe Major Laceration of Femoral Artery 

5 Critical 

Pelvic Fracture, substantial deformation and displacement with associated vascular 

disruption or with major retroperitoneal hematoma; “open book” fracture, blood loss 

greater than 20 % by volume. 

6 Maximum 2° or 3° (or charring to head or trunk or incineration with ≥ 90 % of total body surface. 

7 Unknown Traumatic lower extremity injury died without further evaluation; no autopsy. 

Source: NCSA, NHTSA, NASS – CDS, 1991 - 2000 

Body Region 

The body region variable classifies the injured segment of the body. This allows an injured body 

region to be associated with interior or exterior sources of contact. Additionally, the body region 

may be linked to an intruding component. The distinction between injury sources and intruding 

components lies with the file in which it is reported and the matching with the occupant injury. 

The injury source resides in the occupant injury file and corresponds to a specific injury. The 

intruding component is reported in the vehicle interior file and is linked to a seating position. An 

occupant is reported to occupy a seating position thereby linking an intrusion location with an 

occupant and his injuries. The intruding component is a condensed listing of injury sources and 

associated with seating position. The occupant injuries are attributed to the expanded listing of 

injury sources. If relevant, the intruding component may be linked to one or more injuries and 

may correspond to more than one injury source. 
 8

5. Cases Selected from CDS 

Methodology 

Nearside occupant experience was examined. The parameters by which cases were selected 

varied without sacrificing injury reporting. Based on the intruded areas, an association of the 

nearside occupant injuries attributable to these intruding components was drawn to populate the 

data set. 

Years of Study 

The study spanned the crash reporting years 1991 through 2000 because the fleet age is generally 

accepted to be about ten years and the technology specific to guardrail intrusion present in these 

vehicles would be comparable owing to the CDS selection criteria. The fleet age is unattainable 

using CDS owing to the sample design and case selection criteria. Instead, the selection of crash 

data reported over the ten most recent years is intended to serve as a surrogate for the stipulated 

fleet age. It should also be noted that the ten year time frame is used to ensure an adequate 

sample size. 

Relevant Vehicle Selection 

The vehicle data was restricted to CDS case vehicles (towed passenger vehicles) in non-rollover 

crashes with toe pan, forward of A-Pillar, and/or floor pan intrusion. For reference, this report 

will identify crashes where the case vehicle strikes a fixed object resulting in intrusion to the toe 

pan, floor pan, or forward of the A-Pillar relevant crashes. Cases in which another vehicle is 

struck are also retained for comparative purposes to establish potential common features in 

intrusion threshold evaluation. 

CDS case vehicles are further defined as those, which are involved in, tow away passenger 

vehicle crashes on United States public roadways and reported in NASS selected PARs. 

Although general vehicle and crash environment data may exist for vehicles other than the case 

vehicle in multi-crash environments, specific vehicle and occupant level data will be absent. 

Passenger vehicles are considered in this study because: CDS intrusion and injury data are 

limited to towed light vehicles and the FHWA guideline is relevant only to light vehicles. The 

adequacy of guardrails protecting the entire vehicle fleet mix is the ultimate goal of these 

guardrail guidelines. 

The tow-away vehicle restriction was imposed on the query (forming the basis for this work) 

because of the investigation that ensues. Upon reaching the tow yard, a NASS investigator is 

deployed to examine the vehicle and compile all quantitative data relevant to the crash. From 

this data, other more subtle inferences, based upon experience, may be drawn which are very 

useful in crash reconstruction. 

A restriction based upon the crash configuration is imposed to assure true surrogates in the 

research. Non-planar crashes are excluded owing to the uniqueness of the event, the lack of 

repeatability in laboratory settings, and to their aberrant nature. Additionally, distinguishing 
 9

nearside impact from rollover damage may be difficult, especially following a series of quarter 

turns. 

From the object contacted listing, two categories were created. These were meant to isolate 

vehicle impacts and non-vehicle impacts. Since over 50 attributes are associated with the object 

contacted, small cell sizes were pervasive. For this reason, any impact for which object 

contacted was considered vehicle was retained as such. Among the selected intruding 

components, the impact with another vehicle accounted for slightly more than half of the 

reported impacts. The remaining struck objects were considered non-vehicle impacts. 

The intruded areas were selected upon the FHWA test guideline. These areas also correspond 

with the prevalence in lower limb injuries typically occurring with lower occupant compartment 

deformations. Toe pan and floor pan strikes may be the most obvious selections, however, the 

rationale for forward of the A-pillar is compelling; although upper body injury may be found, the 

majority of the interactions occur with the lower limb. Since the three relevant intrusions are 

considered surrogates for the intrusion and injury patterns caused by a guardrail, these formed 

one of two categories describing intruding components. The second group contemplates the toe 

pan only. The frequency with which this intrusion appears and the damage profile for the 

roadside hardware with respect to the vehicle dictate this selection. 

The intrusion levels were devised based upon the categorical variables defined in CDS (per 

Table 1.) Each level is designed to describe greater intrusion thereby discarding the lower levels 

of intrusion. The groups will, therefore, consist of ever shrinking sample size. 

Occupant Demography 

The occupant data restrictions included are: occupied front right and/or left seating positions, 

age 13 years and greater, seating position matches intrusion location (near-side), intrusion linked 

to an injury, and MAIS. 

The front right and/or left seating positions are specified for several reasons. First, these 

occupants are in vehicle-specified seats equipped with manual and possibly passive restraints. 

The rear seat occupants, as well as any center seating positions, are not generally vulnerable to 

the occupant compartment deformation induced by guardrails, based upon CDS data. Further, 

most of the guardrail crashes with occupant compartment intrusion were frontal or frontal offset 

endangering the lower frontal portion of the vehicle thereby reasserting the selection of the 

intruding components. Structurally, the rear seat occupants are protected from frontal and side 

impact induced by guardrails (10, 11, 12, 1, and 2 o’clock directions of force) by the B-pillar and 

components forward of the B-pillar. The center seating positions should be shielded from this 

type of intrusion owing to their distance from any of the affected sides. 

An age restriction was imposed upon the occupants to address the majority of occupants within 

the vehicle, especially the front seat. Additionally, the physiological development of those 

occupants less than 13 years old might tend to distort the injury patterns of the overall population 

affected by the nearside guardrail impact. NHTSA also recommends that children, ages zero 

through 12 years old, be placed in a rear seating position. As mandated by CDS categorization 

of the age variable, occupant age is coded to 96 years old. If the occupant has reached 97 years 
 10

or older, the age is recorded as 97. Few occupants are categorized with the code of 97. For this 

reason, the demography retains age representation and no cases are sacrificed owing to their 

advanced, yet unspecified age. 

Intrinsic to the coding of CDS, the seating position is set equal to the intrusion area to ensure 

nearside contacts. The intrusion area is assigned an intrusion number that is referenced in the 

occupant injury file. This reference is a linking variable between the relevant intrusion and the 

associated injury. 

The injury data was also qualified to ensure the most accurate intrusion data. Any case with a 

maximum injury severity of abbreviated injury scale (MAIS) 0 through 6 was retained. The 

MAIS is a measurement of risk to life with zero accounting for no injury though six yielding a 

maximum risk to life. The intervening scores are of ascending order and are used to determine 

the severity of injuries sustained as a result of the crash. 

Resultant Injury Dataset Merge Caveats 

As with any data system, cautions must be issued when interpreting the vehicle and occupant 

records within the injury dataset. The following discussion should ensure that any attempt of 

replication would yield the same results. 

Within the data set, an occupant appears as many times as: a qualifying injury record exists or a 

qualifying intruding component record exists. These are inherent to the CDS. This flexibility is 

allowed owing to the unique link existing upon stipulating the year, PSU, case identification 

number, vehicle number, occupant number, and injury number. 

Methodological Adjustments based Upon Limitations

A study of roadside hardware crashes was impossible owing to the inadequate sample size. 

From 1991 through 2000, 69 cases were reported in which a vehicle striking the guardrail was 

the most severe event in the crash. CDS subsumes guardrails within a category known as other 

guardrail, however, guardrails are presumed to comprise the majority of this subset. The 

disaggregation of this category is unavailable without review of photographs and case records. 

An interim report prepared by the George Washington University’s, NHTSA/FHWA National 

Crash Analysis Center (NCAC) for the NCHRP Project 22-15 on compatibility of vehicles and 

roadside hardware, identified and studied the other barrier category. The study concluded that 

the majority of crashes truly involved guardrails impacts including: guardrails, their end 

treatments, and/or their transitions. By way of photographic and case review, the researchers 

were not only able to disaggregate the various guardrail types, they were able to identify whether 

end treatments and/or transitions played a part in the impact. In the absence of sufficient 

guardrail cases, relevant crashes were proposed and outlined below. 

Roadside hardware crashes could not be studied because of their inadequate sample size. A 

natural enlargement of other types of fixed objects that was similar to roadside hardware did not 

exist. Crashes into fixed objects of any kind that resulted in occupant compartment deformation 

into a location where roadside hardware was likely to intrude were aggregated. For comparison, 
 11

the relationship for crashes into other vehicles that intruded into these components was 

examined. 

The relevant case attributes were selected based upon biomechanical grounds. First, the 

intrusions into the passenger compartment inflicted by the guardrails generally occurred in the 

lower regions of the vehicle. As a corollary to this argument, the intrusion into the lower regions 

of the vehicle placed the lower limbs at greater risk for injury. Finally, guardrail impacts had the 

potential for intrusion in the front section of the vehicle. For this reason, the front left and right 

occupants were chosen owing to their proximity to this intrusion. The intruding components, 

most closely addressing the above concerns, were selected: toe pan, floor pan, and forward of 

the A-Pillar. Sample size concerns obligate the FHWA method of examining guardrail intrusion 

compartment into the occupant compartment to be substituted by this method considered 

complementary. As seen in CDS, the majority of guardrail impacts and their possible intrusions 

result in frontal and frontal offset general areas of damage. If any deformation occurs, these 

crashes will generally result in lower occupant compartment deformation, which in the event of 

injury, generally affect the lower extremities. 

It was necessary to determine whether many crashes into roadside hardware sustained intrusions 

into the passenger compartment of less than 15 centimeters. As seen in Tables 3 and 4, this 

became evident for both guardrail and relevant intrusions. It should be noted that this study 

focuses on occupant compartment intrusion and injuries induced by this occurrence. This study 

is meant to examine the interaction between occupant compartment deformation and occupant 

injury, therefore, guardrail impact crashes in which no resultant occupant compartment intrusion 

occurs are excluded because these fall outside of the scope suggested by FHWA during the 

preparation of the analysis. Further, the 15 centimeter threshold will be tested above and below 

these recorded intrusion points because all of the relevant crashes were selected on based upon 

intruding component. It should also be noted that uninjured occupant data for relevant crashes

in which occupant compartment deformation occurs are retained. 

Table 3: Number of Vehicles with Nearside Occupant Intrusion Pursuant to a Guardrail Impact, 

by Intrusion Magnitude (Sample size given in parenthesis.) 

Intrusion Magnitude 

Object 

Contacted 3-7 CM 8-14 CM 15-29 CM 30-45 CM 46-60 CM 

61 OR 

MORE CM Total 

Other Barrier* 5,800 965 2,790 562 68 155 10,339 

(n = 20) (n = 14) (n = 20) (n = 11) (n = 2) (n = 2) (n = 69) 

*No specific category exists in CDS to capture guardrails only, however, they are subsumed within the 

Other Barrier category and comprise a substantial number of these cases.

Source: NCSA, NHTSA, NASS – CDS, 1991 - 2000 
 12

Table 4: Number of Vehicles with Nearside Occupant Intrusion Pursuant to a Toe Pan, Floor Pan, 

or Forward of the A-Pillar Intrusion, by Object Contacted and Intrusion Magnitude 

(Sample size given in parenthesis.) 

Intrusion Magnitude 

Object 

Contacted 3-7 CM 8-14 CM 15-29 CM 30-45 CM 46-60 CM 

61 OR 

MORE 

CM Total 

Vehicle 91,143 86,478 37,264 8,388 4,051 1,235 228,559 

(n = 305) (n = 254) (n = 269) (n = 115) (n = 46) (n = 24) (n = 1013) 

Non-Vehicle 46,912 36,859 27,034 9,711 3,453 2,385 126,353 

(n = 118) (n = 136) (n = 173) (n = 95) (n = 54) (n = 36) (n = 612) 

Total 138,055 123,337 64,298 18,099 7,504 3,620 354,912 

(n = 423) (n = 390) (n = 442) (n = 210) (n = 100) (n = 60) (n = 1625) 

*No specific category exists in CDS to capture guardrails only, however, they are subsumed within the

Other Barrier category and comprise a substantial number of these cases.

Source: NCSA, NHTSA, NASS – CDS, 1991 - 2000 

Over the period 1991 through 2000, 1,567 crashes and 1,625 vehicles involved with relevant 

intrusions were captured, per Table 4. These represented approximately 349,000 crashes and 

354,912 vehicles when the case weighting factors were applied. Of these crashes, the most 

severe event attributable to: fixed object impacts, relevant crashes were 612 (126,000) cases and 

other vehicles were 955 (223,000) cases with their respective vehicle counts reported in Table 4. 

It was acknowledged that factors such as restraint use and occupant age would affect injury 

patterns, however, control for these factors was impossible because of the sample sizes. It was 

assessed whether these factors confounded the data enough to mask a relationship between 

intrusion and injury rather than controlling for them. 

As a final preliminary note, it is generally accepted that high severity injuries aid in identifying 

problem areas. In CDS, however, injury severity is based upon risk of death rather than 

impairment. Of the relevant intrusions, 98 percent of the resulting injuries were attributable to 

lower limb injuries. In general, these injuries are of low risk of mortality, therefore the injury 

severity is low. For this reason, AIS 4 injuries produced in relevant intrusions account for 0.08 

percent of all the injuries produced in relevant intrusions. 

Based on the relevant CDS crashes, it is suggested that mortality may not be the most suitable 

measure for occupant outcome. Lower limb injuries, although of low severity, have the potential 

to produce incapacitating injuries. For this reason it is proposed that the study of injuries greater 

than or equal to AIS 2 should be undertaken. In keeping with the spirit of the guideline rather 

than the corresponding AIS 3 definition of serious injury, a shift from life ending to life 

devastating injuries might better capture the nature of guardrail intrusion into the occupant 

compartment. 
 13

6. Results 

Based on the methodology established for the current phase of research, the resultant data set 

was summarized and subsequently tested for significance. These results are based on injury 

outcomes and crash parameters. 

The injury distribution attributable to the selected intruding components was concentrated at the 

AIS 1 and 2 severities. A small number of injuries were found with injury severity AIS 3 and 4. 

The lower injury severities are consistent with lower limb injuries, as few are life threatening. 

As expected from intrusions in the lower regions of the vehicle, lower limb injuries were the 

most prevalent. Ninety-eight percent of injuries resulting in toe pan, forward of the A-pillar, or 

floor pan intrusions induced lower extremity injuries. Injuries of maximum severity zero were 

retained to adequately represent the crash population, since these were the uninjured segment of 

the intrusion population. 

Contacts with other vehicles tended to induce the majority of the toe pan, forward of A-pillar, 

and floor pan intrusions. These contacts are based on the injuries carrying the highest injury 

severity for each occupant. For this reason, in the event of contact inducing more than one injury 

at the maximum injury level, there may exist more than one entry per contact. This is calculated 

to be approximately 1.9 AIS 2+ injuries per occupant for this data set. Approximately, 53 

percent of intrusions involved another vehicle. By definition, these are generally multi-vehicular 

crashes (non-parked vehicles). Among moderate to maximum occupant injuries occurring in 

vehicles striking trees (small and large, aggregated) with toe pan intrusion, these accounted for 

42 percent of this subset. In contrast, within the same injury severity group but for occupants 

affected by any of the three components, the prevalence of tree contact drops to 24 percent. For 

the selected components, the majority of intrusions were of magnitude 8 through 29 centimeters. 

By components, the toe pan was found to experience the majority of intrusions (80 percent) 

when compared to forward of the A-pillar (6 percent) and floor pan (14 percent) intrusions. 

Not surprisingly, a relationship was found to exist between occupant compartment intrusion and 

injury, even without controlling for important, and seemingly confounding, variables such as 

safety belt usage, age of vehicle occupant, or vehicle body type. This relationship was true for 

fixed objects and vehicles. This suggested that factors were not substantially confounding the 

data. Statistically significant relationships were found for non-minor injuries with intrusions of 8 

to 15 centimeters. This suggested that there was an association between intrusions lower than 

the NCHRP guideline and injury. It was found that 34 percent of relevant crashes into roadside 

hardware had intrusion greater than 15 centimeters, 61 percent had intrusion greater than 8 

centimeters, and 35 percent had intrusion 8 to 15 centimeters. 

The most important result was found to be that the data indicated that many moderate to 

maximum injuries occurred at intrusions less than 15 centimeters. However, the analysis was 

performed without controlling for important variables, such as safety belt usage and age of 

injured occupant. In addition, the result was based on crashes into fixed objects and other 

vehicles, and so might not apply to roadside hardware, per se. 
 14

7. Significance Tests 

Background 

The injury dataset consisted of MAIS 0 through 4 injuries. Significance testing was conducted 

on impact (vehicle or non-vehicle) and component (aggregate of three components or toe pan) by 

intrusion (six categories of magnitude) and injury severity (four combinations of AIS values). 

This operation was performed using SUDAAN (Survey Data Analysis, Software for Statistical 

Analysis of Correlated Data), in conjunction with SAS (Statistical Analysis System). 

Struck Object Categorization for Significance Testing 

The struck objects were separated into two levels, vehicle and non-vehicle, based on CDS data. 

The vehicle category was defined as any vehicle-to-vehicle contact related to injury via intrusion. 

The non-vehicle category subsumed any other object contacted. These included poles, posts, 

natural and man-made roadside hardware, or miscellaneous struck objects related to injury via 

intrusion. 

Component Categorization for Significance Testing 

Two levels of intruding component were devised based on CDS data. The first was an aggregate 

of toe pan, forward of the A-Pillar, and floor pan. The second was comprised solely of the toe 

pan. 

Intrusion Categorization for Significance Testing 

The intrusion magnitude was separated into six categories based on the CDS data. These are as 

follow: 3 centimeters and greater, 8 centimeters and greater, 15 centimeter and greater, 30 

centimeters and greater, 46 centimeters and greater, greater than 61 centimeters. Catastrophic 

and unknown levels of intrusion were omitted owing to their non-numeric and qualitative nature. 

Injury Categorization for Significance Testing 

Four levels of injury severity were used based on CDS data. These are as follow: from AIS 1 

through AIS 6, from AIS 2 through AIS 6, from AIS 3 through AIS 6, from AIS 4 through AIS 

6. The unknown injury level was omitted from the data set. 

Relationship between Intrusion and Injury Scenarios 

In Table 5, the output tests the relations for an impact with a non-vehicle, a fixed object, 

resulting in occupant compartment intrusion from the floor pan, toe pan, or forward of the APillar at intrusion magnitudes above and below 15 centimeters were analyzed for moderate to 

maximum injury severities (AIS ≥ 2) and minor injury severities (AIS ≤ 1). When comparing 

the p-value resulting from the chi square test with the established p-value of 0.05, the 

relationship was found to be significant. This test criterion was applied to all p-values to 

determine significance. (Please reference Section 11, Subsection D for vehicle impacts and 

Subsection E for the output governing fixed object impacts. 

For example in Table 5, AIS ≥ 2, when intrusion is greater than or equal to 15 centimeters in 

relevant crashes, 36 percent of the injuries were of moderate to maximum severity while 64 
 15

percent were of minor severity or the occupant was uninjured. When the intrusion was less than 

15 centimeters, 9 percent of the occupant injuries were of moderate to maximum and 91 percent 

sustained minor injuries or were uninjured. These data indicate a relationship between intrusion 

and injury that is significant with 99.97, (100 %– p-value for the χ

2 test), percent confidence. 

Again, this analysis does not take into account other factors that are related to injury, such as 

safety belt usage. 

Table 5, AIS ≥ 3 also yields a 99.97, (100 %– p-value for the χ

2 test), percent confidence in the 

relationship, however, this is based on a very small sample size. It should be noted that intrusion 

greater than 15 centimeters is present. The zero percent is a minute, rounded value. 

Sample Output 

Table 5: Frequency of Levels of Nearside Occupant 

Injury at Two Intrusion Levels for Intrusion into 

Toe Pan, Floor Pan, or Forward of the A-Pillar 

by a Fixed Object 

Injury 

Severity Intrusion ≥ 15 cm Intrusion < 15 cm 

AIS ≥ 2 36% 9% 

AIS < 2 64% 91% 

p-value for χ

2

 test: 0.0269

AIS ≥ 3 5 % 0 % 

AIS < 3 95 % 100 % 

p-value for χ

2

 test: 0.0284

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000 

Vehicle data has been retained in Appendix 11, Subsection D; however, non-vehicular intrusion 

into the occupant compartment is considered a more adequate surrogate for the guardrail 

intrusion. First, vehicles are geometrically different in mass and design from a guardrail. 

Further, these will deform in a different fashion than the guardrail. Second, the vehicle inflicting 

the intrusion may be moving thereby causing a damage profile unlike that of a stationary object. 

Figures 1 through 4 depict the distribution of significant values of intrusion magnitude and injury 

severity. A concentration of values is evident from 15 centimeters through 61 centimeters. For 

non-vehicle impacts, however, the significant injury severity is consistently distributed from 15 

centimeters through 46 centimeters. As expected, few extreme cases above 61 centimeters exist. 

For vehicle impacts with other vehicles inducing toe pan intrusion, cases are concentrated from 

15 through 61 centimeters. Table 6 accompanies these charts for greater clarity of distribution 

and relevant p-values. The arrows are included in each figure as a reminder of the threshold 

dictated by the current guideline. 

Figures 1 through 4 graphically depict the significant intrusion and injury relationships. For 

example, the significant relationship from Table 5 is indicated by the dot in Figure 3 at the point 

where intrusion is greater than or equal to 15 centimeters and AIS greater than or equal to 2. 

However, in Figure 3, no relationship was found when, for example, intrusion is greater than or 

equal to 15 centimeters and AIS greater than or equal to 4. This might be because of the small 

number of cases. 
 16

Taken together, Figures 1 through 4 indicate a relationship between occupant compartment 

intrusion and injury. They also indicate that many moderate to maximum injuries occur below 

the current NCHRP intrusion threshold of 15 centimeters. These are graphic representation of 

the data presented in Table 6 and may be used interchangeably. It is considered that each 

representation method appeals to different styles of data assimilation. 

The data points on the graphs indicate a significant relationship between the given intrusion and 

injury levels. Based on the outcomes shown in Figures 1 through 4, an indication of relationship 

between intrusion and injury is evident for injuries with as little as eight centimeters of intrusion. 

It should be noted that lack of significance should not be interpreted as zero but instead it may 

indicate an absence of data. 

Figure 1: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by Other 

Vehicle with Toe Pan, Forward of A-Pillar, and/or Floor Pan Intrusions 

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000

A diamond indicates a significant relationship between the given intrusion and 

injury levels

1

2

3

4

Intrusion Magnitude

Injury Severity

(AIS >= Indicated Value)

Intrusion Threshold 

>=8 cm >=15 cm >=30 cm >=46 cm <61 cm
 17

Figure 2: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by Other 

Vehicle with Toe Pan Intrusion 

1

2

3

4

Intrusion Magnitude

Injury Severity

(AIS >= Indicated Value)

>=8 cm >=15 cm >=30 cm >=46 cm >61 cm

Intrusion Threshold

A diamond indicates a significant relationship between the given intrusion and injury 

levels

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000 

Figure 3: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by NonVehicle with Toe Pan, Forward of A-Pillar, and Floor Pan Intrusion 

1

2

3

4

Intrusion Magnitude

Injury Severity

(AIS >= Indicated Value)

>=8 cm >=15 cm >=30 cm >=46 cm >61 cm

Intrusion Threshold

A diamond indicates a significant relationship between the given intrusion and injury 

levels

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000 
 18

Figure 4: Significant Intrusion-(Nearside Occupant) Injury Relationship for Contact by NonVehicle with Toe Pan Intrusion 

1

2

3

4

Intrusion Magnitude

Injury Severity

(AIS >= Indicated Value >=8 cm >=15 cm >=30 cm >=46 cm >61 cm

Intrusion Threshold

A diamond indicates a significant relationship between the given intrusion and injury levels

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000

Table 6 presents a numeric summarization of Figures 1 through 4. Each dot in Figures 1 through 

4 may represent more than one significant relationship, as seen in Table 6. Relevant are the 

many significant relationships found at the various intrusion and injury levels. Also, the 

significant values of intrusion exist as of eight centimeters and greater, as dictated by the current 

guardrail intrusion guideline, and are consistently persistent through 46 centimeters. 

Table 6: P-values of the Significant Intrusion-Nearside Occupant Injury Relationships 

for Toe Pan, Floor Pan, or Forward of the A-Pillar 

Contact by Other 

Vehicle with Toe Pan, 

Forward of A-Pillar, 

and/or Floor Pan 

Intrusions 

Contact by Other 

Vehicle with Toe Pan 

Intrusion 

Contact by Non-vehicle 

with Toe Pan, Forward 

of A-Pillar, and/or Floor 

Pan Intrusions 

Contact by Non-vehicle 

with Toe Pan Intrusion

Intrusion Injury p-value Intrusion Injury p-value Intrusion Injury p-value Intrusion Injury p-value

≥8 cm AIS ≥ 1 0.0007 ≥8 cm AIS ≥ 3 0.0330 ≥8 cm AIS ≥ 2 0.0269 ≥8 cm AIS ≥ 3 0.0363

≥8 cm AIS ≥ 2 0.0129 ≥15 cm AIS ≥ 1 0.0008 ≥8 cm AIS ≥ 3 0.0284 ≥15 cm AIS ≥ 1 0.0100

≥8 cm AIS ≥ 3 0.0040 ≥15 cm AIS ≥ 2 0.0000 ≥15 cm AIS ≥ 1 0.0036 ≥15 cm AIS ≥ 2 0.0172

≥15 cm AIS ≥ 1 0.0000 ≥15 cm AIS ≥ 3 0.0002 ≥15 cm AIS ≥ 2 0.0159 ≥15 cm AIS ≥ 3 0.0131

≥15 cm AIS ≥ 2 0.0000 ≥30 cm AIS ≥ 1 0.0025 ≥15 cm AIS ≥ 3 0.0175 ≥30 cm AIS ≥ 1 0.0190

≥15 cm AIS ≥ 3 0.0001 ≥30 cm AIS ≥ 2 0.0035 ≥30 cm AIS ≥ 1 0.0014 ≥30 cm AIS ≥ 2 0.0012

≥30 cm AIS ≥ 1 0.0009 ≥30 cm AIS ≥ 3 0.0113 ≥30 cm AIS ≥ 2 0.0005 ≥30 cm AIS ≥ 3 0.0409

≥30 cm AIS ≥ 2 0.0003 ≥46 cm AIS ≥ 1 0.0190 ≥30 cm AIS ≥ 3 0.0254 ≥46 cm AIS ≥ 1 0.0102

≥30 cm AIS ≥ 3 0.0007 ≥46 cm AIS ≥ 2 0.0107 ≥46 cm AIS ≥ 1 0.0015 ≥46 cm AIS ≥ 2 0.0171

≥46 cm AIS ≥ 1 0.0053 ≥61 cm AIS ≥ 1 0.0003 ≥46 cm AIS ≥ 2 0.0049 ≥61 cm AIS ≥ 1 0.0472

≥46 cm AIS ≥ 2 0.0037 ≥61 cm AIS ≥ 2 0.0004 ≥46 cm AIS ≥ 3 0.0485

≥46 cm AIS ≥ 3 0.0286 ≥61 cm AIS ≥ 1 0.0079

≥61 cm AIS ≥ 1 0.0001

≥61 cm AIS ≥ 2 0.0001

 

 

 

 

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000 
 19

8. Analysis of Moderate to Maximum Injuries 

Based on the significance tests, it was concluded that injuries of severity (AIS) 2 and greater 

merited further study. This is also consistent with the spirit of the NCHRP’s “serious injury” 

stipulation, as applied to lower limb injuries. It should be noted that the roadside safety 

community also contemplates the traditional AIS definition when defining serious injury 

resulting from occupant compartment deformation pursuant to a guardrail intrusion. For this 

reason, both definitions are presented in this section. In Section 11, Subsection C, injury 

concentrations were evident in the band of occupants sustaining AIS 2 injuries. This is 

consistent with lower limb injuries and dictated by their prevalence in this crash type. Further, 

occupant compartment intrusion magnitudes 8 through 29 centimeters posed greatest AIS 2 

injury frequency. AIS 1 injury, as in all crash types with injured occupants, are the most 

prevalent (121,000) but nearly equivalent to the AIS 2 injuries (108,000.) 

Tables 7 and 8 describe intrusion magnitude associated with nearside occupant injury 

distribution based on categories of object contacted and intruding component, for AIS 2+ and 

AIS 3+ severities. Figures 5 and 6 describe nearside occupant injury distribution, for AIS 2+ and 

AIS 3+ severities. The overwhelming representation of lower limb injury is of particular interest 

in each figure, as is its prevalence among the relevant intrusion. It should be noted that the 

extremely low frequencies might represent as few as one case indicating a potentially rare 

situation. (Please recall that CDS is a weighted sample of tow away crashes.) 

Table 7: AIS 2+ Nearside Occupant Injuries by Object Contacted, Intruding Component 

and Injured Body Region

Non-Vehicle 

UPPER 

EXTREMITY CHEST HEAD

LOWER 

EXTREMITY ABDOMINAL 

Toe Pan 0 0 0 48,166 48 

Forward of A-Pillar 54 47 0 1,260 0 

Floor Pan 0 55 0 8,200 0 

Selected Intruding Components 54 102 0 57,626 48 

Vehicle 

UPPER 

EXTREMITY CHEST HEAD

LOWER 

EXTREMITY ABDOMINAL 

Toe Pan 66 0 16 50,057 0 

Forward of A-Pillar 185 1,517 65 3,822 603 

Floor Pan 0 0 0 8,358 0 

Selected Intruding Components 251 1,517 81 62,237 603 

Source: NCSA, NHTSA, NASS – CDS, 1991 - 2000
 20

Table 8: AIS 3+ Nearside Occupant Injuries by Object Contacted, Intruding Component 

and Injured Body Region

Non-Vehicle 

UPPER 

EXTREMITY CHEST HEAD 

LOWER 

EXTREMITY ABDOMINAL 

Toe Pan 0 0 0 4,266 0 

Forward of A-Pillar 54 0 0 317 0 

Floor Pan 0 0 0 676 0 

Selected Intruding Components 54 0 0 5,259 0 

Vehicle 

UPPER 

EXTREMITY CHEST HEAD 

LOWER 

EXTREMITY ABDOMINAL 

Toe Pan 66 0 16 7,350 0 

Forward of A-Pillar 0 826 22 471 90 

Floor Pan 0 0 0 425 0 

Selected Intruding Components 66 826 38 8,246 90 

Source: NCSA, NHTSA, NASS – CDS, 1991 - 2000

Figure 5: Distribution of AIS 2+ Nearside Occupant Injuries from Toe Pan, Floor Pan, and 

Forward of the A-Pillar Intrusion for Vehicles Striking a Fixed Object 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

UPPER

EXTREMITY

CHEST HEAD LOWER

EXTREMITY

ABDOMINAL 

Injured Body Region

Distribution of AIS 2+ Injuries

Toe Pan

FRONT SIDE PANEL

FLOOR PAN

Source: NCSA, NHTSA, NASS – CDS, 1991 - 2000
 21

Figure 6: Distribution of AIS 3+ Nearside Occupant Injuries from Toe Pan, Floor Pan, and 

Forward of the A-Pillar Intrusion for Vehicles Striking a Fixed Object 

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

UPPER EXTREMITY

CHEST 

HEAD 

LOWER EXTREMITY

ABDOMINAL 

Injured Body Region

Distribution of AIS 3+ Injuries

Toe Pan

FRONT SIDE PANEL

FLOOR PAN

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000 

Based on Tables 7 and 8, it is evident that the lower limb is the most vulnerable. Nearly 100 

percent of the AIS 2 through 6 injuries for occupants in vehicles with toe pan intrusion induced 

by a fixed object affects the lower limb. Intrusion from forward of the A-pillar inflicts injuries 

upon upper body regions, as well as lower extremities. The floor pan induces lower limb injury 

patterns similar to the other intruding components. The aggregate, relevant intrusion yields the 

same result with regard to the probability of injury. 

Vehicle-to-vehicle contacts are retained in view of their prevalence; however, the focus of this 

work has been the non-vehicle contact. It is surmised that non-vehicle intrusion more closely 

resembles the geometry of a guardrail as described in the previous section. 

Results by Intruding Component 

The intruding components were divided into toe pan and all components combined (relevant 

intrusion.) The toe pan was found to pose a greater risk of injury. A caveat must be issued with 

regard to several confounding factors. These factors may include but are not restricted to deltav, crash conditions, and restraint use. 

As expected, the risk of injuries of moderate severity and greater resulting from nearside toe pan 

intrusion increases as the intrusion magnitude increases, per Figure 7. The greater the 

deformation of the occupant compartment the more vulnerable the nearside occupant becomes. 

The percentages represent the likelihood that an AIS 2 through 6 injury will occur at each of the 
 22

six intrusion magnitude levels. It should be noted that severe injuries, AIS 4, are the highest 

reported for the previously defined intrusion configurations. Since the lower injury severities are 

culpable for irreparable orthopedic damage, these injuries may be interpreted as life devastating, 

as opposed to life threatening. 

Figure 7: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 2 in 

Vehicles with Toe Pan Striking Vehicle 

31% 41%

67% 63% 78% 77%

0%

20%

40%

60%

80%

100%

Greater than

or equal to 3

cm

Greater than

or equal to 8

cm

Greater than

or equal to 15

cm

Greater than

or equal to 30

cm

Greater than

or equal to 46

cm

Greater than

61 cm

Intrusion Magnitude

Relative Frequency of 

AIS 2+

Injury 

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000

Upon combining the relevant intrusion in Figure 8, the results are found to be consistent but not 

statistically significant. The p-values yielded from the Chi-Square testing were used to 

determine the lack of significance. Although, yielding values above the 0.05 confidence level, 

the patterns were seen to be consistent with those found in the toe pan only scenario. One 

possible explanation for the consistent results is that strengthening the guideline may benefit toe 

pan more than other components. 

Figure 8: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 2 in 

Vehicles with Toe Pan, Forward of A-Pillar, and/or Floor Pan Intrusion Striking Non-Vehicle 

26% 36%

49% 54%

79% 77%

0%

20%

40%

60%

80%

100%

Greater than

or equal to 3

cm

Greater than

or equal to 8

cm

Greater than

or equal to 15

cm

Greater than

or equal to 30

cm

Greater than

or equal to 46

cm

Greater than

61 cm

Relative Frequency of AIS 

Intrusion Magnitude

2+

Injury 

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000 
 23

In comparison, note the percentages reported for AIS 3 and greater in Figures 9 and 10 are much 

smaller but increase, as would be expected, for increasing intrusion magnitudes. The standard 

errors for these calculations are exceedingly high unlike those for the AIS 2 and greater 

calculations. The relative frequencies are based on a very small sample size. Also, the y-axes of 

Figures 9 and 10 report a lower maximum value for the y-axis than do Figures 7 and 8. This was 

chosen to avoid obscuring the smaller relative frequencies. These findings are included to 

comply with a literal interpretation of injury severity based upon the guideline, as it corresponds 

to the AIS definition. 

Figure 9: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 3 in 

Vehicles with Toe Pan Striking Vehicle 

4% 6%

11% 15%

31%

9%

0%

5%

10%

15%

20%

25%

30%

35%

Greater than

or equal to 3

cm

Greater than

or equal to 8

cm

Greater than

or equal to 15

cm

Greater than

or equal to 30

cm

Greater than

or equal to 46

cm

Greater than

61 cm

Intrusion Magnitude

Relative Frequency of AIS 3+ 

Injury

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000 

Figure 10: Relative Frequency of Nearside Occupant Injuries Greater than or Equal to AIS 3 in 

Vehicles with Toe Pan, Forward of A-Pillar, and/or Floor Pan Intrusion Striking Non-Vehicle

3% 5% 9% 13%

29%

9%

0%

5%

10%

15%

20%

25%

30%

35%

Greater than

or equal to 3

cm

Greater than

or equal to 8

cm

Greater than

or equal to 15

cm

Greater than

or equal to 30

cm

Greater than

or equal to 46

cm

Greater than

61 cm

Intrusion Magnitude

Relative Frequency of AIS 3+ 

Injury

Source: NCSA, NHTSA, NASS – CDS, 1991 – 2000
 24

9. Summary of Results 

The data indicate that many moderate to maximum injuries occur at occupant compartment 

intrusions less than 15 centimeters, the current FHWA guideline. However, the analysis was 

performed without controlling for important variables, such as safety belt usage and age of 

injured occupant. In addition, the result was based on crashes into fixed objects and other 

vehicles, and so might not apply to roadside hardware, per se. This was based on relevant 

crashes that resulted in approximately 58,000 non-vehicle nearside occupant injuries and 62,000 

vehicle nearside occupant injuries. 

In addition, it was found that a predominance of injuries to the lower limb was evident. The data 

set was reflecting a succession of unlike events. Finally, a non-uniform vehicle fleet may alter 

the results, slightly. 

The non-vehicle contacts represented contact with a disparate collection of objects. Hence, 

distinct behavior can be expected from the various contacting objects. The intrusion induced 

will also vary based upon the object. 

Statistically significant relationships were found for non-minor injuries with occupant 

compartment intrusions of 8 to 15 centimeters. This suggested that there was an association 

between intrusions lower than the NCHRP testing protocol, as interpreted by FHWA, and injury. 

It was found that 26 percent of relevant crashes into roadside hardware had intrusion greater 

than or equal to 15 centimeters, 61 percent had intrusion greater than or equal to 8 centimeters, 

and 35 percent had intrusion 8 through 14 centimeters. 

Vehicle Striking Vehicle 

About half of the injuries are attributable to a vehicle striking another vehicle, a multi-vehicle 

crash (contact with non-parked vehicles.) Owing to the complexity of this crash configuration, 

many factors occur simultaneously thereby weakening the relationship of injury severity and 

intrusion magnitude. However, several unique events generally occur in this scenario. Finally, 

the many variations within the current fleet mix cause incompatibilities in the intrusion patterns. 

Fixed Object Struck 

As a result of the many different attributes described by the object contacted variable and the 

overwhelming representation of vehicle impacts, an analysis of similarly performing groups of 

objects was undertaken for all non-vehicle objects struck. This aggregation tends to yield a 

disparate collection of objects that behave in different fashions when struck and impart distinct 

intrusion and injury patterns. 

The guideline (Powers, 2003) prevents many injuries, however, reducing the allowable intrusion 

in the guideline could prevent many more injuries. The injuries of severity (AIS) 2 and greater 

appear to be most related to intrusions. Injuries of AIS 3 and greater could potentially be more 

attributable to increasing delta-v. As expected the intrusion magnitude increased as the injury 

severity rose. (Please reference Section 11, Subsection C.) 
 25

10. Recommendations for Future Study 

Based on the results, there may be several paths to improve the data set supporting any proposed 

guideline change. Possible solutions could include: examining more years in CDS, expanding 

search by generalizing scope to include GES, working with anecdotal data, controlling for 

vehicle body types, and/or examining all cases involving intrusion into the toe pan, floor pan, or 

forward of the A-Pillar. 

Examine Several More Years of NASS - CDS 

This approach would yield more data. It may also be more responsive to the current vehicle fleet 

mix. Additionally, more cases were reported in earlier years of CDS. Finally, more experience 

in user needs would be present. 

These advantages are tempered by the fewer variables available to qualify a crash in earlier 

years. Technological advances allow for much better data quality and accuracy in later years of 

CDS owing to greater and more precise instrumentation. 

Expand Search by Generalizing Scope to Include GES 

The immediate benefit exists in the greater number of cases. The GES is a nationally 

representative sample of crashes occurring in the United States. 

GES, although the repository for more cases, are less specific. Owing to the broader nature, 

vehicle inspections are absent thereby forfeiting any intrusion data. The non-medically assessed 

injury severity scale is based on the police officer’s assessment of the occupant. 

Work with Anecdotal Data 

Although few cases exist in individual non-vehicular objects contacted, these could be viewed 

anecdotally to ascertain injury patterns and their related intrusions. These cases could stimulate 

research and study into related areas or establish surrogates that exhibit statistical significance. 

Data of this sort would not merit statistical analysis. Additionally, there may be limited 

applicability for the anecdotal data. 

Control for Vehicle Body Types 

Controlling for vehicle body types would allow accurate conclusions and extrapolations to be 

made regarding the impacted vehicle based on the striking vehicle’s geometry. The current form 

of the study aggregates all vehicles without regard for the body type of the striking or struck 

vehicles. It is proposed to aggregate corporate cousins (vehicle classified as geometrically 

similar although produced by different manufacturers) rather than by vehicle body type. 

With the advent of smaller vehicles, the incompatibility is not only seen amongst the vehicle 

classes but with the protective roadside hardware. It is theorized that guardrails standards were 

designed to protect an older vehicle fleet that was different to the one active today. Further, 

some smaller vehicles may be exposed to damage, if softer structures, unintended structures are 

making contact with the guardrail. As a corollary, larger vehicles may not be afforded the 
 26

intended protection and could even damage the roadside appurtenance, if an inappropriate 

vehicle structure makes contact with it. SUVs, for instance, may not be adequately protected. 

Further, the guardrail pursuant to an SUV impact may sustain damage. Via real-world crash 

outcomes and subsequently testing to generate simulations, it would be prudent to establish that 

the guardrail will not induce vehicle damage owing to possibly outdated design 

standards/parameters. 

An overpowering disadvantage is the small data sets associated with each vehicle body type. 

Analysis may become inappropriate. 

Examine All Toe Pan, Floor Pan, or Forward of the A-Pillar Cases 

The intrusion to nearside occupant injury relationship can be further studied by controlling for 

key factors, such as age and safety belt use. Similar patterns have been established in the vehicle 

and fixed objects data subsets. It is, therefore, proposed that the vehicle and fixed objects 

subsets should be combined to obtain a sufficient sample for a controlled analysis. 

A minor disadvantage exists in the loss of struck object definition, however, this is counteracted 

by the sample size benefits to be obtained. 
 27

11. Appendix 

A. Data Sets 

The following data sets were consulted in the preparation of this report. Although data found in 

the Fatality Analysis Reporting System and National Automotive Sampling System - General 

Estimates System were excluded from the analysis, the content was considered during the 

preparation of the preliminary phase and in subsequent recommendations. 

Fatality Analysis Reporting System 

National Automotive Sampling System 

National Automotive Sampling System (NASS) case collection began in 1979. NASS is 

composed of two systems - the Crashworthiness Data System (CDS) and the General Estimates 

System (GES). Both systems are based on cases selected from a sample of police crash reports. 

CDS data focus on passenger vehicle crashes, and are used to investigate injury mechanisms to 

identify potential improvements in vehicle design. GES data focus on the bigger overall crash 

picture, and are used for problem size assessments and tracking trends. The system was 

established as part of an effort to reduce motor vehicle crashes, injuries, and deaths on our 

nation's highways. NASS enjoys a wide audience: government scientists, engineers, public 

health professionals, and university researchers. 

NASS – GES 

GES provides basic injury data based on a nationally representative probability sample of policereported crashes. For a case to become eligible for GES, it must have a completed PAR, the 

crash must involve at least one motor vehicle traveling on a traffic way, and result in property 

damage, injury, or death. GES started sampling cases in 1988. 

Data are reported in three files. These files are the Accident, Vehicle, and Person Files. The 

injury data are based on the injury severity scale with the categories including K (killed), A 

(incapacitating injury), B (non-incapacitating injury), C (possible injury), and O (no injury). 
 28

NASS - CDS 

CDS yields a comprehensive description of the crash events based on the PAR. These cases are 

then investigated to obtain a complete file on the vehicles involved in the crash, the geometry of 

the crash location, the interaction of the vehicles with the geometry/location attributes, the 

demography of the passenger vehicle occupants, and the injury mechanisms/patterns, if any 

exist, for each of the occupants. With regard to this report, the strength of CDS lies in the injury 

severity ratings and the associated injury sources. The abbreviated injury scale (AIS) is used to 

assess risk of fatality. The AIS injury categories are defined as follows: 

 

 AIS 1 – Minor 

 AIS 2 – Moderate 

 AIS 3 – Serious 

 AIS 4 – Severe 

 AIS 5 – Critical 

 AIS 6 – Maximum (untreatable) 

Currently, CDS integrates 11 files: Accident Description, Accident, Event, General Vehicle, 

Occupant Assessment, Occupant Injury, Person Profile, Accident Type, Vehicle Exterior, 

Vehicle Profile, Vehicle Interior. The Accident Description, Person Profile, Accident Type, and 

Vehicle Profile are text descriptions of the people, crash, and vehicles as summarized by the 

investigator. The Accident and Event files convey the most general crash elements such as 

roadway geometry, crash type, numbers of vehicles and occupants, offending roadside elements, 

and general vehicle classifications. The General Vehicle, Vehicle Exterior, and Vehicle Interior 

files convey vehicle related attributes of the crash. The Occupant Assessment and Occupant 

Injury files compile the crash demography placing the occupant in the vehicle and associating 

him with crash attributes and injury mechanisms. 

The elements used for the study were taken from the Occupant Assessment and Occupant Injury 

files. These files indicated the age, seating position, injury level and injury type for each 

occupant within the struck vehicle. These elements were then merged with the Vehicle Interior 

file to retain only nearside occupant injuries associated with relevant intrusion. 
 29

B. Selected CDS Definitions 

The following variables were used in part or unrestricted for the intrusion analysis. The entire 

description is retained to elucidate the finer points of the query. Object contacted, vehicle body 

type, injury severity, and injured body region variables were each compacted to capture a greater 

number of cases and to ease statistical analysis. The following definitions are taken from the 

CDS format files. 

Object Contacted 

VALUE OBJCONT 

 . = 'NO EVENT/CDC' 

 01 = 'VEHICLE NO. 1' 02 = 'VEHICLE NO. 2' 

 03 = 'VEHICLE NO. 3' 04 = 'VEHICLE NO. 4' 

 05 = 'VEHICLE NO. 5' 06 = 'VEHICLE NO. 6' 

 07 = 'VEHICLE NO. 7' 08 = 'VEHICLE NO. 8' 

 09 = 'VEHICLE NO. 9' 10 = 'VEHICLE NO. 10' 

 11 = 'VEHICLE NO. 11' 

 31 = 'ROLLOVER-OVERTRN' 56 = 'OTHER BARRIER' 

 32 = 'ROLLOVER-ENDOVER' 

 33 = 'FIRE/EXPLOSION' 57 = 'FENCE' 

 34 = 'JACKKNIFE' 58 = 'WALL' 

 35 = 'INTRAUNIT DAMAGE' 59 = 'BUILDING' 

 36 = 'NONCOLLISION INJ' 60 = 'DITCH/CULVERT' 

 38 = 'OTH NONCOLLISION' 61 = 'GROUND' 

 39 = 'UNK NONCOLLISION' 62 = 'FIRE HYDRANT' 

 63 = 'CURB' 

64 = 'BRIDGE' 

68 = 'OTH FIXED OBJECT' 

 41 = 'SMALL TREE' 

 69 = 'UNK FIXED OBJECT' 

 42 = 'LARGE TREE' 70 = 'NOT IN TRAN LGTVEH' 

 43 = 'BUSH' 71 = 'NOT IN TRAN HVYVEH' 

 44 = 'EMBANKMENT' 

 72 = 'PEDESTRIAN' 45 = 'BREAKAWAY POLE' 73 = 'CYCLIST' 

 74 = 'OTH NONMOTORIST' 

75 = 'VEHICLE OCCUPANT' 50 = 'SMALL POLE' 76 = 'ANIMAL' 

 77 = 'TRAIN' 

 51 = 'MEDIUM POLE' 78 = 'TRAILER, DISCONN' 

 79 = 'OBJ FELL FRM VEH' 

 52 = 'LARGE POLE' 88 = 'OTH NONFIXED OBJ' 

 89 = 'UNK NONFIXED OBJ' 

 53 = 'UNK SIZE POLE' 

 98 = 'OTHER EVENT' 

 54 = 'CONCRETE BARRIER' 55 = 'IMPACT ATENUATOR' 

 .U = 'UNK EVENT/OBJECT'; 
 30

Vehicle Body Type 

BODYTYPE 

 01 = 'CONVERTIBLE' 

 02 = '2DR SEDAN/HT/CPE' 

 03 = '3DR/2DR HATCHBAK' 

 04 = '4-DR SEDAN/HDTOP' 

 05 = '5DR/4DR HATCHBAK' 

 06 = 'STATION WAGON' 

 07 = 'HATCHBACK DR UNK' 

 08 = 'OTHER AUTOMOBILE' 

 09 = 'UNK AUTO TYPE' 

 10 = 'AUTO BASE PICKUP' 11 = 'AUTO BASED PANEL' 

 12 = 'LARGE LIMOUSINE' 

 13 = 'THREE-WHEEL AUTO' 

 14 = 'COMPACT UTILITY' 

 15 = 'LARGE UTILITY' 

 16 = 'UTILITY STAWAGON' 19 = 'UTILITY UNK BODY' 

 20 = 'MINIVAN' 

 21 = 'LARGE VAN' 

 22 = 'STEP VAN <10K LB' 

 23 = 'VAN BASE MTRHOME' 

 24 = 'VAN BASED SCHBUS' 25 = 'VAN BASED OTHBUS' 

 28 = 'OTHER VAN TYPE' 

 29 = 'UNKNOWN VAN TYPE' 

 30 = 'COMPACT PICKUP' 

 31 = 'LARGE PICKUP' 

 32 = 'PICKUP/CAMPER' 33 = 'CONVERT PICKUP' 

 39 = 'UNK PICKUP TRUCK' 

 40 = 'CAB CHASSIS' 

 41 = 'TRUCK BASE PANEL' 

 42 = 'LT TRK MOTORHOME' 

 45 = 'OTH LIGHT TRUCK' 48 = 'UNK LIGHT TRUCK' 

 49 = 'UNK LIGHT VEH' 

 50 = 'SCHOOL BUS' 58 = 'OTHER BUS' 

 59 = 'UNKNOWN BUS' 

 60 = 'STEP VAN >10K LB' 61 = 'SU TRUCK 10-19.5' 

 62 = 'SU TRUCK 19.5-26' 

 63 = 'SU TRUCK >26K LB' 

 64 = 'SU TRUCK GVW UNK' 

 65 = 'MH TRK MOTORHOME' 

 67 = 'BOBTAIL TRACTOR' 68 = 'TRK-TRAC 1 TRAIL' 

 69 = 'TRK-TRAC 2 TRAIL' 

 70 = 'TRK-TR UNK TRAIL' 

 78 = 'UNK MED/HVY TRK' 

 79 = 'UNKNOWN TRUCK' 

 80 = 'MOTORCYCLE' 

 81 = 'MOPED' 

 82 = '3 WHEEL MC/MOPED' 

 88 = 'OTH MOTORED CYCL' 

 89 = 'UNK MOTORED CYCL' 

 90 = 'ATV AND ATC' 

 91 = 'SNOWMOBILE' 

 92 = 'FARM EQUIPMENT' 

 93 = 'CONSTRUCT EQUIP' 

 97 = 'OTHER VEHICLE TYPE' 
 31

 98 = 'NOT APPLICABLE' 

 .N = 'NOT COLLECTED' 

 .U = 'UNKNOWN BODY TYPE'; 

Seating Position 

VALUE SEATPOS 

 11 = 'FRONT LEFT SIDE' 31 = 'THIRD LEFT' 

 12 = 'FRONT MIDDLE' 32 = 'THIRD MIDDLE' 

 13 = 'FRONT RIGHT SIDE' 33 = 'THIRD RIGHT' 

 14 = 'FRONT OTHER' 34 = 'THIRD OTHER' 

 15 = 'FRONT ON/IN LAP' 35 = 'THIRD ON/IN LAP' 

 21 = 'SECOND LEFT' 41 = 'FOURTH LEFT' 

 22 = 'SECOND MIDDLE' 42 = 'FOURTH MIDDLE' 

 23 = 'SECOND RIGHT' 43 = 'FOURTH RIGHT' 24 = 'SECOND OTHER' 44 = 'FOURTH OTHER' 

 25 = 'SECOND ON/IN LAP' 45 = 'FOURTH ON/IN LAP' 

 97 = 'UNENCLOSED AREA' 

 98 = 'OTHER SEAT' .U = 'UNKNOWN';

Intrusion Location 

VALUE INLOC 

 11 = 'FRONT LEFT' 

 12 = 'FRONT MIDDLE' 13 = 'FRONT RIGHT' 

 21 = 'SECOND LEFT' 

 22 = 'SECOND MIDDLE' 

 23 = 'SECOND RIGHT' 

 31 = 'THIRD LEFT' 

 32 = 'THIRD MIDDLE' 

 33 = 'THIRD RIGHT' 

 41 = 'FOURTH LEFT' 

 42 = 'FOURTH MIDDLE' 43 = 'FOURTH RIGHT' 

 97 = 'CATASTROPHIC' 

 98 = 'OTH ENCLOSE AREA' .U = 'UNKNOWN'; 
 32

Intruding Component 

VALUE INCOMP 

 01 = 'STEER ASSEMBLY' 

 02 = 'INSTR PANEL LEFT' 

 03 = 'INSTR PANEL CTR' 

 04 = 'INSTR PANEL RT' 

 05 = 'TOE PAN' 

 06 = 'A-PILLAR' 

 07 = 'B-PILLAR' 

 08 = 'C-PILLAR' 

 09 = 'D-PILLAR' 

 10 = 'FRONT SIDE PANEL' 11 = 'DOOR PANEL' 

 12 = 'REAR SIDE PANEL' 

 13 = 'ROOF/CONVERT TOP' 

 14 = 'ROOF SIDE RAIL' 

 15 = 'WINDSHIELD' 

 16 = 'WINDSHIELD HDR' 17 = 'WINDOW FRAME' 

 18 = 'FLOOR PAN' 

 19 = 'BACKLIGHT HEADER' 

 20 = 'FRONT SEAT BACK' 

 21 = 'SECOND SEAT BACK' 

 22 = 'THIRD SEAT BACK' 23 = 'FOURTH SEAT BACK' 

 24 = 'FIFTH SEAT BACK' 

 25 = 'SEAT CUSHION' 

 26 = 'BACK DOOR/PANEL' 

 27 = 'OTHER COMPONENT' 

 30 = 'HOOD' 31 = 'OUTSIDE SURFACE' 

 32 = 'OTH EXTERIOR OBJ' 

 33 = 'UNK EXTERIOR OBJ' 

 97 = 'CATASTROPHIC' 

 98 = 'UNLIST COMPONENT' 

 .U = 'UNKNOWN'; 

Intruding Magnitude 

VALUE INMAG 

 1 = '3-7 CENTIMETERS' 2 = '8-14 CENTIMETERS' 

 3 = '15-29 CENTIMETER' 

 4 = '30-45 CENTIMETER' 5 = '46-60 CENTIMETER' 

 6 = '61 OR MORE CM' 

 7 = 'CATASTROPHIC' .U = 'UNKNOWN'; 
 33

Dominant Crush Direction 

VALUE CDRIR 

 1 = 'VERTICAL' 

 2 = 'LONGITUDINAL' 

 3 = 'LATERAL' 

 7 = 'CATASTROPHIC' 

 .U = 'UNKNOWN'; 

Injury Severity Scales 

VALUE INJSEV 

 0 = 'O NO INJURY' 

 1 = 'C POSSIBLE INJ' 

 2 = 'B NONINCAPAC' 

 3 = 'A INCAPACITATING' 

 4 = 'K KILLED' 

 5 = 'U SEVERITY UNK' 

 6 = 'DIED PRIOR' 

 .U = 'UNKNOWN';

VALUE AIS 

 0 = 'NOT INJURED' 

 1 = 'MINOR INJURY' 2 = 'MODERATE INJURY' 

 3 = 'SERIOUS INJURY' 

 4 = 'SEVERE INJURY' 

 5 = 'CRITICAL INJURY' 

 6 = 'MAXIMUM INJURY' 

 7 = 'INJURED, UNK SEV' 

 .N = 'NOT COLLECTED' 

 .U = 'UNK IF INJURED'; 

Injured Body Region 

VALUE $BDYREGN 

 'A' = 'ARM' 

 'B' = 'BACK' 

 'C' = 'CHEST' 

 'E' = 'ELBOW' 

 'F' = 'FACE' 

 'H' = 'HEAD' 

 'K' = 'KNEE' 

 'L' = 'LEG/LOWER' 

 'M' = 'ABDOMEN' 

 'N' = 'NECK' 

 'P' = 'PELVIC/HIP' 

 'Q' = 'ANKLE/FOOT' 

 'R' = 'FOREARM' 

 'S' = 'SHOULDER' 

 'T' = 'THIGH' 

 'U' = 'INJURED/UNK REG' 

 'W' = 'WRIST/HAND' 

 'X' = 'UPPER LIMBS' 

 'Y' = 'LOWER LIMBS'; 

C. Number of Nearside Occupant, Age 13 Years and Older, Injuries 

that were Associated with a Relevant Intrusion 

Table 9: Intrusion into Occupant Compartment by Intruding Component, AIS 1 

Controlling for AIS=1 
 34

Intrusion into Intruding Component 

Occupant 

Compartment TOE PAN FRONT SIDE PANEL FLOOR PAN Total

3-7 CENTIMETERS 23,469 3,004 1,390 27,863

8-14 CENTIMETERS 28,438 5,907 2,258 36,603

15-29 CENTIMETER 25,085 5,197 5,552 35,834

30-45 CENTIMETER 6,796 3,453 2,509 12,758

46-60 CENTIMETER 3,902 534 644 5,079

61 OR MORE CM 2,413 0 405 2,818

Total 90,102 18,094 12,758 120,954

 

Table 10: Intrusion into Occupant Compartment by Intruding Component, AIS 2

Controlling for AIS=2 

Intrusion into Intruding Component 

Occupant 

Compartment TOE PAN FRONT SIDE PANEL FLOOR PAN Total

3-7 CENTIMETERS 16,782 415 1,290 18,487

8-14 CENTIMETERS 18,792 214 7,575 26,581

15-29 CENTIMETER 29,251 4,072 3,975 37,298

30-45 CENTIMETER 10,548 781 509 11,837

46-60 CENTIMETER 6,541 282 1,158 7,981

61 OR MORE CM 4,741 10 1,005 5,756

Total 86,655 5,773 15,512 107,940
 35

 

Table 11: Intrusion into Occupant Compartment by Intruding Component, AIS 3

Controlling for AIS=3 

Intrusion into Intruding Component 

Occupant 

Compartment TOE PAN FRONT SIDE PANEL FLOOR PAN Total

3-7 CENTIMETERS 1,025 162 106 1,293

8-14 CENTIMETERS 1,338 32 85 1,454

15-29 CENTIMETER 4,153 921 550 5,624

30-45 CENTIMETER 1,712 309 70 2,092

46-60 CENTIMETER 2,876 141 232 3,249

61 OR MORE CM 594 10 58 662

Total 11,699 1,573 1,101 14,373

 

Table 12: Intrusion into Occupant Compartment by Intruding Component, AIS 4 

Controlling for AIS=4 

Intrusion into Intruding Component 

Occupant 

Compartment TOE PAN FRONT SIDE PANEL FLOOR PAN Total

3-7 CENTIMETERS 0 127 0 127

8-14 CENTIMETERS 0 20 0 20

15-29 CENTIMETER 0 0 0 0

30-45 CENTIMETER 0 60 0 60

46-60 CENTIMETER 0 0 0 0

61 OR MORE CM 0 0 0 0

Total 0 206 0 206
 36

D. Relevant Intrusions Resulting from Impact with Other Vehicle 

Table 13: Relative Frequency of Bifurcated Nearside 

Occupant Injury Levels Occurring at Bifurcated 

Intrusion Levels in Crashes with Impacts with Other 

Vehicles Inducing Toe Pan, Floor Pan, and/or Forward 

of the A-Pillar Damage 

Intrusions in Toe Pan, Floor Pan, 

or A-Pillar by Contact with 

Another Vehicle 

Intrusions in Toe Pan by Contact 

with Another Vehicle 

Intrusion Injury 

Relative 

Frequency of 

Injury Level at 

Intrusion Level Intrusion Injury

Relative 

Frequency of 

Injury Level at 

Intrusion Level 

≥ 3 cm AIS ≥ 1 33.65 % ≥ 3 cm AIS ≥ 1 52.46 % 

≥ 3 cm AIS ≥ 2 16.74 % ≥ 3 cm AIS ≥ 2 28.37 % 

≥ 3 cm AIS ≥ 3 3.11 % ≥ 3 cm AIS ≥ 4 0.00 % 

≥ 3 cm AIS ≥ 4 0.07 % ≥ 8 cm AIS ≥ 1 64.49 % 

≥ 8 cm AIS ≥ 1 43.65 % ≥ 8 cm AIS ≥ 2 33.72 % 

≥ 8 cm AIS ≥ 2 21.29 % ≥ 8 cm AIS ≥ 3 6.96 % 

≥ 8 cm AIS ≥ 3 4.42 % ≥ 8 cm AIS ≥ 4 0.00 % 

≥ 8 cm AIS ≥ 4 0.05 % ≥ 15 cm AIS ≥ 1 93.07 % 

≥ 15 cm AIS ≥ 1 66.00 % ≥ 15 cm AIS ≥ 2 61.50 % 

≥ 15 cm AIS ≥ 2 42.03 % ≥ 15 cm AIS ≥ 3 14.67 % 

≥ 15 cm AIS ≥ 3 10.41 % ≥ 15 cm AIS ≥ 4 0.00 % 

≥ 15 cm AIS ≥ 4 0.12 % ≥ 30 cm AIS ≥ 1 100.00 % 

≥ 30 cm AIS ≥ 1 82.44 % ≥ 30 cm AIS ≥ 2 89.12 % 

≥ 30 cm AIS ≥ 2 65.44 % ≥ 30 cm AIS ≥ 3 19.90 % 

≥ 30 cm AIS ≥ 3 15.91 % ≥ 30 cm AIS ≥ 4 0.00 % 

≥ 30 cm AIS ≥ 4 0.43 % ≥ 46 cm AIS ≥ 1 100.00 % 

≥ 46 cm AIS ≥ 1 99.33 % ≥ 46 cm AIS ≥ 2 88.14 % 

≥ 46 cm AIS ≥ 2 77.98 % ≥ 46 cm AIS ≥ 3 19.76 % 

≥ 46 cm AIS ≥ 3 19.57 % ≥ 46 cm AIS ≥ 4 0.00 % 

≥ 46 cm AIS ≥ 4 0.00 % ≥ 61 cm AIS ≥ 1 100.00 % 

≥ 61 cm AIS ≥ 1 100.00 % ≥ 61 cm AIS ≥ 2 98.18 % 

≥ 61 cm AIS ≥ 2 98.32 % ≥ 61 cm AIS ≥ 3 18.71 % 

≥ 61 cm AIS ≥ 3 17.29 % ≥ 61 cm AIS ≥ 4 0.00 % 

≥ 61 cm AIS ≥ 4 0.00 % 
 37

E. Relevant crashes

Table 14: Relative Frequency of Bifurcated Nearside 

Occupant Injury Levels Occurring at Bifurcated 

Intrusion Levels in Crashes with Impacts with NonVehicles (Fixed Objects) Inducing Toe Pan, Floor Pan, 

and/or Forward of the A-Pillar Damage 

Intrusions in Toe Pan, Floor Pan, 

or A-Pillar by Contact with a 

Non-Vehicle (Fixed Object) 

Intrusions in Toe Pan by Contact 

with a Non-Vehicle (Fixed Object) 

Intrusion Injury 

Relative 

Frequency of 

Injury Level at 

Intrusion Level Intrusion Injury

Relative 

Frequency of 

Injury Level at 

Intrusion Level 

≥ 3 cm AIS ≥ 1 52.73 ≥ 3 cm AIS ≥ 1 61.67 

≥ 3 cm AIS ≥ 2 25.69 ≥ 3 cm AIS ≥ 2 30.51 

≥ 3 cm AIS ≥ 3 3.46 ≥ 3 cm AIS ≥ 3 4.01 

≥ 3 cm AIS ≥ 4 0.00 ≥ 3 cm AIS ≥ 4 0.00 

≥ 8 cm AIS ≥ 1 62.19 ≥ 8 cm AIS ≥ 1 67.20 

≥ 8 cm AIS ≥ 2 35.68 ≥ 8 cm AIS ≥ 2 41.14 

≥ 8 cm AIS ≥ 3 5.41 ≥ 8 cm AIS ≥ 3 6.22 

≥ 8 cm AIS ≥ 4 0.00 ≥ 8 cm AIS ≥ 4 0.00 

≥ 15 cm AIS ≥ 1 83.07 ≥ 15 cm AIS ≥ 1 97.46 

≥ 15 cm AIS ≥ 2 48.96 ≥ 15 cm AIS ≥ 2 66.50 

≥ 15 cm AIS ≥ 3 8.54 ≥ 15 cm AIS ≥ 3 10.97 

≥ 15 cm AIS ≥ 4 0.00 ≥ 15 cm AIS ≥ 4 0.00 

≥ 30 cm AIS ≥ 1 90.86 ≥ 30 cm AIS ≥ 1 94.44 

≥ 30 cm AIS ≥ 2 53.82 ≥ 30 cm AIS ≥ 2 62.96 

≥ 30 cm AIS ≥ 3 13.18 ≥ 30 cm AIS ≥ 3 15.47 

≥ 30 cm AIS ≥ 4 0.00 ≥ 30 cm AIS ≥ 4 0.00 

≥ 46 cm AIS ≥ 1 100.00 ≥ 46 cm AIS ≥ 1 100.00 

≥ 46 cm AIS ≥ 2 78.61 ≥ 46 cm AIS ≥ 2 77.78 

≥ 46 cm AIS ≥ 3 28.79 ≥ 46 cm AIS ≥ 3 31.12 

≥ 46 cm AIS ≥ 4 0.00 ≥ 46 cm AIS ≥ 4 0.00 

≥ 61 cm AIS ≥ 1 100.00 ≥ 61 cm AIS ≥ 1 100.00 

≥ 61 cm AIS ≥ 2 77.09 ≥ 61 cm AIS ≥ 2 77.12 

≥ 61 cm AIS ≥ 3 9.17 ≥ 61 cm AIS ≥ 3 8.84 

≥ 61 cm AIS ≥ 4 0.00 ≥ 61 cm AIS ≥ 4 0.00 
 38

12. References 

Eskandarian, A., Bahouth, G., Digges, K., Eigen, A., Bronstad, M., "NCHRP Project 22-15: 

Summary of Phase I Research and Revised Work Plan, Improving the Compatibility of Vehicles 

and Roadside Safety Hardware," National Cooperative Highway Research Program, 

Transportation Research Board, January, 2001. 

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