Development of Requirements and Functional Specifications for
Crash Event Data Recorders

Final Report

 

PDF Version

FOREWORD

This document is disseminated under the sponsorship of the Department of Transportation in the interest of information exchange. The United States Government assumes no liability for its contents or use thereof.

The contents of this report reflect the views of the contractor, who is responsible for the accuracy of the data presented herein. The contents do not necessarily reflect the official policy of the United States Department of Transportation.

This report does not constitute a standard, specification, or regulation.

The United States Government does not endorse products or manufacturers. Trade or manufacturers’ names appear herein only because they are considered essential to the object of this document.

 

ACKNOWLEDGEMENTS

This project was funded by the Federal Highway Administration Intelligent Transportation Systems/Joint Program Office and managed by the Federal Motor Carrier Safety Administration. The authors are grateful for the support and contributions of many USDOT staff members who provided valuable input and direction to the project including:  Amy Houser (FMCSA), Deborah Freund (FMCSA), Ralph Craft (FMCSA), John Hinch (NHTSA), Gary Toth (NHTSA), and Kate Hartman (FHWA).

ACRONYMS AND ABBREVIATIONS

3D                               Three Dimensional

∆V                               Delta V, Change in Velocity

ABS                             Anti-Lock Braking System

AC                               Alternating Current

ACC                            Automatic Cruise Control

Ack                              Acknowledge

ACN                            Automatic Collision Notification

AMPS                         Advanced Mobile Phone Service

APP                             Accelerator Pedal Position

ASCII                          American Standard Code for Information Exchange

ASR                             Acceleration Slip Regulation

ATA                            American Trucking Associations

ATC                            Automatic Traction Control

AVSC                          Automatic Vehicle Speed Control

BCI                              Bulk Current Injection

BTU                             British Thermal Units

CCVS                          Cruise Control/Vehicle Speed

CCW                           Counterclockwise

CFC                            Channel Frequency Class

CMV                           Commercial Motor Vehicle

CTI                              Central Tire Inflation

CVR                            Cockpit Voice Recorder

CW                              Clockwise

DC                               Direct Current

DDU                            Driver Display Unit      

DED                            Data Element Definition

DERM                         Diagnostic Energy Reserve Module

DIU                             Driver Interface Unit

DL                               Driver’s License

DOF                            Degree-of-Freedom

DRL                             Daytime Running Lamps

DSRC                          Dedicated Short Range Communication

EBS                             Electronic Braking System

ECBS                          Electronically Controlled Braking System

ECM                            Electronic/Engine Control Module

ECU                            Engine Control Unit/ Electronic Control Unit

EDR                             Event Data Recorder

EEPROM                    Electrically-Erasable Programmable Read-Only Memory

EMI                             Electromagnetic Interference

EMS                            Emergency Medical Services

ESN                             Electronic Serial Number

ESV                             Enhanced Safety Vehicle

FAA                            Federal Aviation Administration

FARS                          Fatal Accident Reporting System

FCWS                         Forward Collision Warning System

FDR                             Flight Data Recorder

FHWA                         Federal Highway Administration

FMCSA                       Federal Motor Carrier Safety Administration

FMVSS                       Federal Motor Vehicle Safety Standards          

FOT                             Field Operational Test

g                                  Acceleration of Gravity

GES                             General Estimates System

GHz                             GigaHertz

GIS                              Geographic Information System

GM                              General Motors

GMT                            Greenwich Mean Time

GPRMC                      Recommended Minimum Specific GPS/Transit Data

GPS                             Global Positioning System

GVWR                        Gross Vehicle Weight Rating

HDOP                         Horizontal Dilution of Precision

HVAC                         Heating Ventilation and Air Conditioning

Hz                                Hertz

I/O                               Input/Output

ID                                Identification

IEEE                            Institute of Electrical and Electronic Engineers

IrDA                            Infrared Data Association        

ISM                             InterStellar Medium

ISO                              International Standards Organization

ITS/JPO                       Intelligent Transportation Systems/Joint Program Office

IVI                               Intelligent Vehicle Initiative

IWI                              Independent Witness Incorporated

JPL                              Jet Propulsion Laboratory

kbps                             Kilobits Per Second

KHz                             KiloHertz

kW                              Kilowatt(s)

Lat                               Latitude

LDWS                         Lane Departure Warning System

LED                             Light-Emitting Diode

Long                            Longitude

LRMS                          Location Reference Message System

LTCCS                        Large Truck Crash Causation Study

MB                              Megabytes

Mbps                           Mega-Bits Per Second

MHz                            MegaHertz

MMUCC                     Model Minimum Uniform Crash Criteria           

MV                              Motor Vehicle

MVEDR                      Motor Vehicle Event Data Recorder

N                                 Newton

NASA                         National Aeronautical and Space Administration

NASS                          National Automotive Sampling System

NAV                            Navigation System

NCHRP                       National Cooperative Highway Research Program

NCIC                          National Crime Information Center

NCSA                         National Center for Statistics and Analysis

NHTSA                       National Highway Traffic Safety Administration

NMEA                         National Maritime Electronics Association

NTSB                          National Transportation Safety Board

NVM                           Non-Volatile Memory

OEM                           Original Equipment Manufacturer

OMC                           Office of Motor Carriers

PAR                             Police Accident Report

PC                               Personal Computer

PCMCIA                     Personal Computer Memory Card International Association

PCU                            Pressure Control Unit

PDA                            Personal Digital Assistant

PDOF                          Principal Direction of Force

PGN                            Parameter Group Number

PID                              Perimeter Identification

POI                              Point of Impact

PSD                             Power Spectral Density

PTO                             Power Take Off

RF                               Radio Frequency

RH                               Relative Humidity

ROM                           Read Only Memory

RP                               Recommended Practice

RPM                            Revolutions Per Minute

SAE                             Society of Automotive Engineers

SCI                              Special Crash Investigation

SDM                            Sensing Diagnostic Module

SPN                             Suspect Parameter Number

SRS                             Supplemental Restraint System

T&B                            Truck and Bus

TCD                            Traffic Control Device

TMA                            Truck Manufacturers Association

TMC                            Technology and Maintenance Council

TRB                             Transportation Research Board

US                               United States

USB                             Universal Serial Bus

USDOT                       United States Department of Transportation

UTC                            Universal Time Coordinated

VDC                            Volts Direct Current

VDR                            Vehicle Data Recorder

VIN                             Vehicle Identification Number

VRTC                          Vehicle Research and Test Center

WG                              Working Group

 

EXECUTIVE SUMMARY

This report presents the results of a Federal Highway Administration (FHWA) Intelligent Transportation Systems/Joint Program Office (ITS/JPO) project, in collaboration with the Truck Manufacturers Association (TMA). In this project, a comprehensive requirements analysis defined specific crash event data recorder (EDR) requirements and functional specifications to facilitate the reconstruction of crashes involving large trucks. These requirements and specifications were developed through a review of previous and on-going EDR work and an analysis of CMV crash data. Using this information, specific data elements were ranked in the following three tiers to define crash characteristics in crashes involving commercial motor vehicles (CMVs):

 

Tier 1 – The minimum required data elements for a crash EDR on CMVs.

Tier 2 – Additional data elements to the data elements in tier 1 that would permit further analysis of crashes involving CMVs.

Tier 3 – A complete set of data crash elements to thoroughly analyze crashes involving CMVs, including the data elements listed in tiers 1 and 2 above.

After the tiers of data elements were established, a cost effectiveness analysis was conducted to estimate the costs of the data elements in each of the three tiers and to determine whether one or more data elements would significantly increase the cost of an EDR.

 

Tier 1 data elements included:

·        Acceleration (Longitudinal, Lateral, and Vertical)

·        Accelerator Pedal Position/Time History

·        Brake Status/Pressure/Time History (includes Antilock Brake System)

·        Belt Status

·        Engine Speed

·        Steering Wheel Angle/Time History

·        Time/Date

·        Transmission Gear Selection

·        Vehicle Speed

·        Wheel Speeds

·        Vehicle Identification

·        Vehicle Path

 

Tier 2 data elements, in addition to Tier 1 data elements, included:

·        Airbag Status

·        Battery and System Voltage

·        Cruise Control Status

·        Engine Retarder System Status

·        Traction Control Status

·        Clutch Position

·        Headlight Status

·        Running Light Status

·        Turn Signal Status

·        Warning Light Status

·        Windshield Wiper Status

·        Vehicle Load, Stability Control, Yaw and Tilt Angle (Advanced sensor installation)

 

Tier 3 included data elements, in addition to Tier 1 and 2 data elements, as well as:

 

·        Brake Stroke

·        Brake System Pressure

·        Distance to Intersection

·        Driver – Eye Glance Position

·        Driver – Fatigue Status

·        Horn Use / Status

·        Roadway Surface Friction

·        Running Light Status

·        Side Object Detector

·        Tire Pressure

·        Truck Headway

·        Truck Lane Position

·        Video Imaging – Driver

·        Video Imaging – Roadside Environment

 

In addition to the data elements tiers, requirements were also developed for EDR components, hardware, software, sensors, and databases. Furthermore, the project addressed issues such as, the physical attributes of the device, crash/environmental survivability, availability of appropriate sensors; data storage and retrieval; crash event trigger algorithms; accuracy and reliability; calibration; and maintainability. In summary, the Development of Requirements and Functional Specifications for Crash Event Data Recorders project can provide a foundation for a future design of a crash EDR for CMVs. 

   

TABLE OF CONTENTS

Section                                                                                                                                        Page

INTRODUCTION .. 1

TASK 1 – ANALYZE CRASH DATA............................................................................................................................................ 2

INTRODUCTION .. 2

LARGE TRUCK CRASH PROFILE . 2

LARGE TRUCK CRASH LOCATIONS . 7

CRASH CONFIGURATIONS . 8

ROADWAY CONDITIONS . 9

ENVIRONMENTAL CONDITIONS . 9

CRASH CHARACTERISTICS . 11

LTCCS CASE SELECTION .. 12

LTCCS CASE ANALYSIS . 16

SUMMARY .. 19

TASK 2 – REVIEW LITERATURE . 20

INTRODUCTION .. 20

LITERATURE REVIEW ... 20

NHTSA RECOMMENDATIONS . 21

MODEL MINIMUM UNIFORM CRASH CRITERIA DATA ELEMENTS REVIEW ... 23

IN-VEHICLE NETWORK DATA ELEMENTS REVIEW ... 23

ON-BOARD LAND-VEHICLE MAYDAY REPORTING INTERFACE REVIEW ... 24

COMPLETE SET OF DATA ELEMENTS . 24

TASK 3 – DEVELOP FUNCTIONAL SPECIFICATIONS . 25

INTRODUCTION .. 25

DATA ELEMENT TIERS . 25

DATA ELEMENT COST-EFFECTIVENESS ANALYSIS . 26

FUNCTIONAL SPECIFICATIONS . 27

Crash Event Triggers . 27

Algorithms . 27

EDR OPERATIONAL ENVIRONMENT .. 28

Temperature –   SAE J1455 . 28

Humidity – SAE J1455 and SAE J1211 . 29

Salt Atmosphere –   SAE J1455 . 29

Immersion and Splash (Water, Chemicals, and Oils) –   SAE J1455 . 29

Steam Cleaning/Pressure Washing –   SAE J1455 . 30

Fungus –   SAE J1455 . 30

Dust, Sand, and Gravel Bombardment –   SAE J1455 . 30

Altitude –   SAE J1455 . 30

Mechanical Vibration –   SAE J1455 . 31

Mechanical Shock –   SAE J1455 . 31

Steady-State Electrical Characteristics –   SAE J1455 . 32

Voltage Transients–   SAE J1455 . 33

Electrical Noise and Electro-static/-magnetic Compatibility Characteristics 34

Back-Up Power 36

Long-Term Data Storage . 36

Size, Weight, and Mounting Method . 36

EDR SURVIVABILITY .. 37

SYSTEM CONNECTIVITY .. 42

EDR DATA RETRIEVAL . 43

EDR Operational Concerns . 43

Interface Configurations and Data Retrieval Process . 43

Data Retrieval Protocol 45

EDR Data File Format 46

Number of Events Stored in EDR Memory . 46

Multiple Events and Overlap of Events . 47

Overall Accuracy . 47

System and Data Repeatability . 47

System Calibration and Maintenance . 48

Incorporation with Fleet Management Tools . 48

Expandability . 49

CONCLUSION .. 51

 

List of Tables

Table                                                                                                                                          Page

1 ...... Crash Frequency by Body Type for GES Years 2000 and 2001. 3

2 ...... Crash Frequency by Body Type. 4

3 ...... Crash Frequency by Crash Configuration – 2000 GES. 5

4 ...... Crash Frequency by Crash Configuration – 2001 GES. 6

5 ...... Crash Location. 7

6  ..... Crash Relation to Roadway. 7

7  ..... Crash Relation to Junction. 8

8  ..... Crash Manner of Collision. 9

9 ...... Crash Roadway Alignment 9

10 .... Crash Roadway Profile. 9

11   .. Crash Atmospheric Conditions. 10

12  ... Crash Surface Conditions. 10

13  ... Crash Lighting Conditions. 10

14  ... First Harmful Event 12

15  ... Sample of Cases from the LTCCS. 15

16  ... Data from LTCCS Cases. 16

17  ... Data Elements and Frequency of Occurrence in LTCCS Case Analysis. 18

18 .... Summary of EDR Event Algorithms. 28

21  ... SAE J1455 Temperature Extremes for Heavy-Duty Truck/Tractor 29

22 .... SAE J1455 12-Volt and 24-Volt Operating Characteristics. 33

23 .... SAE J1455 Transient Voltage Characteristics. 34

24 .... Various SAE Electrical Noise Test Standards. 35

25 .... EDR Data Survivability Parameters. 38

27 .... EDR Data Element Record Format 46

28 .... Examples of Dual-Use EDR Technologies. 48

 

List of Figures

Figure                                                                                                                                         Page

1....... EDR System Connectivity Block Diagram.. 42

2 ...... Simplified EDR Block Diagram.. 52

 

INTRODUCTION

Crash Event Data Recorders (EDRs) can provide critical information on crashes involving commercial motor vehicles (CMVs) to improve the current understanding of vehicle safety and support the development of future crash countermeasures. This Federal Highway Administration Intelligent Transportation Systems/Joint Program Office (FHWA ITS/JPO) project, in collaboration with the Truck Manufacturers Association (TMA), consisted of a comprehensive requirements analysis, which defined specific EDR requirements and functional specifications to facilitate the reconstruction of crashes involving large trucks (gross vehicle weight rating (GVWR) of more than 10,000 pounds). Specifically, the project built upon the findings of the National Highway Traffic Safety Administration (NHTSA) sponsored Truck and Bus Event Data Recorder Working Group (T&B EDR WG).

Three main tasks were performed in this project:

1.      Task 1 – Develop Requirements for an EDR through Crash Analysis

2.      Task 2 – Review Previous and Ongoing Efforts with Respect to EDRs and Vehicle Data Recorders (VDRs)

3.      Task 3 – Develop Functional Specifications for an EDR for CMVs.

Task 1 consisted of initially analyzing the National Crash Sampling System’s (NASS’s) General Estimates System (GES) data to characterize large truck (GVWR of more than 10,000 pounds) crashes. Then, a profile of large truck crashes established through the use of NASS GES data was used to select crashes from the NHTSA/Federal Motor Carrier Safety Administration (FMCSA) Large Truck Crash Causation Study (LTCCS). 133 cases were selected from the LTCCS for in-depth crash analysis. The analysis of these cases resulted in a list of data elements that could be recorded by an EDR and be useful for crash reconstruction.

Task 2 consisted of reviewing EDR literature, uses, and recommendations from several government agencies and other stakeholders. The majority of the recommendations focused on the types of data elements that should be collected in an EDR. In addition, the data elements available on the in-vehicle data networks (Society of Automotive Engineers (SAE) J-1587 and SAE J-1939) were reviewed.

Task 3 involved using the information in Task 1 and 2 to rank data elements in the following three tiers to define crash characteristics in crashes involving CMVs:

 

Tier 1 – The minimum required data elements for a crash EDR on CMVs.

Tier 2 – Additional data elements to the data elements in tier 1 that would permit further analysis of crashes involving CMVs.

Tier 3 – A complete set of data crash elements to thoroughly analyze crashes involving CMVs, including the data elements listed in tiers 1 and 2 above.

After the categories of data elements were established, a cost effectiveness analysis was conducted to estimate the costs of the data elements in each of the three tiers and to determine whether one or more data elements would significantly increase the cost of an EDR. In addition, operational (environmental and electrical) specifications for an EDR were created, along with methods of communication with an EDR in order to off-load an EDR’s data.

TASK 1 – ANALYZE CRASH DATA

INTRODUCTION

This section summarizes the work performed on Task 1 – Develop Requirements for an EDR through Crash Analysis. The basis for this analysis included previous work from NHTSA, FMCSA, National Transportation Safety Board (NTSB), along with a comprehensive requirements analysis to define specific EDR requirements and functional specifications for the reconstruction of crashes involving large trucks. A requirements-based approach applied large truck crash data from the NHTSA/FMCSA LTCCS to derive requirements for an EDR that would facilitate crash reconstruction. These findings were used to develop functional specifications and requirements for an EDR that could be successfully implemented in large trucks.

LARGE TRUCK CRASH PROFILE

In order to select a proper population of truck crashes for analysis, an evaluation of the large truck crash population was performed using the NASS GES. GES data come from a nationally representative sample of police reported motor vehicle crashes of all types, from minor to fatal. The GES began operation in 1988 to identify traffic safety problem areas, provide a basis for regulatory and consumer initiatives, and form the basis for cost and benefit analyses of traffic safety initiatives. The information is used to estimate how many motor vehicle crashes of different kinds take place and what happens when they occur. Although various sources suggest that about half of the motor vehicle crashes in the country are not reported to the police, the majority of these unreported crashes involve only minor property damage and no significant personal injury. By restricting attention to police-reported crashes, GES concentrates on those crashes of greatest concern to the highway safety community and the general public.

GES data are used in traffic safety analyses by NHTSA and other USDOT agencies. In order for a crash to be eligible for the GES sample, a police accident report (PAR) must be completed where the crash involved at least one motor vehicle traveling on a trafficway, resulting in property damage, injury, or death. These crash reports are chosen from 60 areas that reflect the geography, roadway mileage, population, and traffic density of the United States. GES data collectors make weekly visits to approximately 400 police jurisdictions in the 60 areas across the U.S., where they randomly sample about 50,000 PARs each year. The data collectors obtain copies of the PARs and send them to a central contractor for coding. No other data are collected beyond the selected PARs.

Trained data entry personnel interpret and code data directly from the PARs into an electronic data file. Approximately 90 data elements are coded into a common format. Some element modification takes place every other year in order to meet the changing needs of the traffic safety community. To protect individual privacy, no personal information, such as names, addresses, or specific crash locations, is coded. During coding, the data are checked electronically for validity and consistency. After the data file is created, further quality checks are performed on the data through computer processing and by the data coding supervisors.

To understand an EDR’s utilization environment, an evaluation of GES data was conducted to determine the type of crashes that large trucks are currently involved in. For this analysis, two years of GES data, from 2000 and 2001, were examined to determine if the trends observed in the data were consistent across a two year period or if a “spike” in the data record. After an examination of these results, data spikes were not apparent in the data, and the two years of data were believed to be sufficient for this analysis.

In 2000 and 2001, over 11 million vehicle crashes were recorded in GES. As shown in Table 1, medium/heavy truck crashes constituted 3.4% and 3.5% of the population in 2000 and 2001, respectively. (Medium/heavy trucks in GES are defined as large trucks with a GVWR of more than 10,000 pounds.) The data for these various large truck body types are also shown in Table 2. The crash analysis for this project focused on these vehicles.

Table 1
Crash Frequency by Body Type for GES Years 2000 and 2001

                                                                                                                                   

 

 

 

 

  Table 2
Crash Frequency by Body Type

                                                                                                                                   

 

The GES data file also provided the identification of crash configurations, which described the relative motion of each vehicle in multiple vehicle crashes or other descriptive features in single vehicle crashes. Table 3 and Table 4 illustrate the crash configurations for data years 2000 and 2001. The crash configurations were consolidated into the major descriptions within each configuration. 

 

Table 3
Crash Frequency by Crash Configuration – 2000 GES

*Sum not equal to 100% due to rounding.

 

Table 4
Crash Frequency by Crash Configuration – 2001 GES

*Sum not equal to 100% due to rounding.

LARGE TRUCK CRASH LOCATIONS

GES crash data records also provided insight into the roadways where large truck crashes occur. Table 5 illustrates the distribution of vehicle crashes between the interstate highway system and other roadways. (An “Interstate Highway” is an FHWA designation for those roadways that are part of the Dwight D. Eisenhower System of Interstate and Defense Highways.) According to this data, approximately 21% of large truck crashes occurred on the interstate highways.

Table 5
Crash Location

 

Table 6 provides additional data on the location of large truck crashes. The Relation to Roadway Variable in the GES system provided data on the location of the first harmful event where the first impact occurred. The results provided data that is linked to the truck’s operational profile. While the predominant location for the first harmful event is on the roadway, several crashes occurred in the parking lane or on the roadside.

Table 6
Crash Relation to Roadway

 

As shown in Table 7, additional descriptive data regarding crash locations was provided by the Relation to Junction Variable within the GES. In 2000 and 2001, approximately 50 percent of large truck crashes occurred between intersections in non-interchange, non-junction areas.

Table 7
Crash Relation to Junction

                     *Sum not equal to 100% due to rounding.

CRASH CONFIGURATIONS

The crash configuration distribution for large trucks was analyzed by examining the Manner of Collision Variable within the GES. The Manner of Collision Variable (GES Variable A7) indicates the orientation of the vehicles in a collision. Table 8 illustrates this distribution for large trucks for in 2000 and 2001.

The Manner of Collision distribution for large trucks was dominated by four configurations; “no collision,” “rear-end” (which includes the truck being hit from behind and the truck striking the rear of other vehicle), “angle,” and “sideswipe, same direction.”   These four crash configurations accounted for over 94% of large truck crashes in 2000 and 2001.

 

Table 8
Crash Manner of Collision

 

ROADWAY CONDITIONS

The roadway and environmental conditions data provided useful information for the development of EDR requirements. These statistics revealed that large truck crashes primarily occurred on straight and level roadways. Table 9 and Table 10 show the distribution of large truck crashes by roadway alignment and roadway profile.

Table 9
Crash Roadway Alignment

 

 

Table 10
Crash Roadway Profile

 

ENVIRONMENTAL CONDITIONS

As shown in Table 11, the GES data revealed that large truck crashes primarily occurred in daylight hours with no adverse weather conditions. A smaller proportion of the crashes occurred in the rain.

Table 11
 Crash Atmospheric Conditions

 

As shown in Table 12, the roadway surface conditions data mirrored the data from atmospheric conditions. Crashes for large trucks occurred predominantly on dry roads.

Table 12
Crash Surface Conditions

 

The lighting conditions under which these crashes occurred are shown in Table 13. The predominant lighting condition for large truck crashes was daylight.

 

Table 13
Crash Lighting Conditions

CRASH CHARACTERISTICS

The GES crash data file provided information about the characteristics of each large truck crash. While not as detailed as the data retrieved from the LTCCS, this data provided useful information about the kinematic environment where crashes occur and the severity of the crashes.

The GES Variable “First Harmful Event” describes the first property damaging or injury producing event in the crash. This variable identifies the type of crash such as, vehicle-to-vehicle, single-vehicle crash, or other type. Table 14 provides data on the first harmful event for large trucks crashes as listed in the 2001 and 2002 GES data file. The most harmful event in a large percentage of crashes was collision with a “Vehicle in Transport.”  This value described vehicle-to-vehicle crashes between moving vehicles. The percentages of crashes involving large trucks within this category in 2000 and 2001 were 74.0% and 76.7%, respectively.

Table 14
First Harmful Event

LTCCS CASE SELECTION

To support the development of distinct tiers of the most critical data elements, “real world” crash data from the LTCCS were analyzed to facilitate determining the most beneficial types of recorded data to reconstruct crashes involving large trucks. The profile of large truck crashes established through the use of NASS GES data was used to select crashes from the NHTSA/FMCSA LTCCS. The LTCCS is the first national study to determine the reasons and associated factors contributing to serious large truck crashes. Using this information, agencies within the US Department of Transportation (USDOT) and others could gain an understanding of crashes and work to implement effective countermeasures to reduce the occurrence and severity of these crashes.

In the LTCCS, researchers and State truck inspectors collected information on a sample of large truck crashes. The NASS-trained researchers worked in unison with state inspectors at a crash scene to investigate the facts and causes of the truck-involved crash. The NASS-trained researchers worked with state inspectors at a crash scene to investigate the facts and causes of the truck-involved crash. NASS researchers depended on the voluntary participation and cooperation of law enforcement agencies, hospitals, physicians, medical examiners, coroners, tow yard operators, garages, vehicle storage facilities, and the individuals involved in crashes. Cooperation was established with police agencies and hospitals to provide copies or transcripts of official records. Tow yards, police impound yards, and crash involved parties were contacted to obtain permission to inspect vehicles. Personal or telephone contact was made with interviewees to obtain information about occupant characteristics and crash circumstances.

A specific set of data was retrieved from each LTCCS case. Data acquired in each case included, but was not limited to:

·        First Harmful Event

·        Case Summary by Investigator

·        Critical Pre-Crash Event

·        Violations Charged

·        Critical Reason for Critical Event

·        Attempted Avoidance Maneuver

·        Scene Diagram

·        Relation to Roadway

·        Police Reported Travel Speed

·        Relation to Junction

 

The selection of crash cases from the LTCCS was a critical step in the development tiers of data elements for an EDR. The GES profile of large truck crashes previously developed was used to select a similar profile of cases from the LTCCS. The ideal situation would be for the LTCCS case profile to match the GES crash profile previously established. Since the processing of all LTCCS data was not complete at the time of this effort, the cases used for this analysis were those that successfully passed all quality assurance steps within the LTCCS as of March 2003. 

The case assessment involved filtering the available cases by crash type. The crash type variable and configuration codes in the LTCCS and NASS GES files are identical, which allowed a comparison of crash populations in both files. Only 213 crash cases were initially available for use in this assessment. An initial review of these cases reduced the number of cases to 180. Cases were dropped due to incomplete quality assurance checks, or the truck was not an active participant in the crash, such as when a truck is parked on the side of the road with the engine off and no driver present. A second round of case reviews eliminated further cases. Since the LTCCS had not completed the release of all data, a number of cases were withdrawn for further quality assurance procedures.

The final number of LTCCS cases for the EDR assessment was 133. The description of the crash compiled by the investigator and the scene diagram were critical in the identification of data elements for an EDR. Each individual case provided input for a list of data elements that would assist in the reconstruction of that case. The summing of the data elements for the various cases would show which elements would have the most utility in the various crash categories and which elements would be the least useful.

The distribution of the crash types and configurations included in the sample was examined to determine the fit with the previously developed GES profile. Table 15 illustrates the final distribution of the crash types in the LTCCS cases.

In the profile established from the GES data, the four most numerous crash categories were:

·        Same Trafficway, Same Direction

·        Changing Trafficway, Vehicle Turning

·        Single Driver

·        Miscellaneous (Backing)

 

In the population of LTCCS cases, these rash categories were the same. Yet, the remaining three categories (Same Trafficway, Opposite Direction; No Impact; and Intersecting Paths (Vehicle Damage)) were not in the same order in both crash profiles. As a result, they were represented in the final LTCCS cases, but not in the same order.  

In the profile of LTCCS cases, there was an under-representation of “Same Trafficway, Same Direction” cases. These cases are typically rear-end or sideswipe/angle crashes. Although these types were underrepresented, they comprised a sufficient number for use in the assessment. Also, the “No Impact” crash types were not present in the LTCCS cases. These crashes typically included jack-knife crashes, comprising a small but significant population of the large truck crash population. Given these constraints, the match of the LTCCS cases to the GES Crash profile was adequate for a clinical analysis that would be used to determine tiers of data element for an EDR, in addition to other information sources.     

 

 

 

 

 

Table 15
Sample of Cases from the LTCCS

*Sum not equal to 100% due to rounding.

 

 LTCCS CASE ANALYSIS

The goal of the analysis of LTCCS cases was to develop a set of data elements for an EDR that would permit the reconstruction crashes involving large trucks. The elements recorded from the LTCCS cases are shown in Table 16.

Table 16
Data from LTCCS Cases

Form Type	Variable Number
General Vehicle	7 –   Body Type 11 – Police Reported Travel Speed 17 – Violations Charged 20 – Relation to Roadway 21 – Relation to Junction 25 – Number of Travel Lanes 30 – Roadway Alignment 31 – Roadway Profile 32 – Roadway Surface Type 33 – Roadway Surface Condition 40 – Light Condition 41 – Atmospheric Condition 44 – Manner of Collision 45 – First Harmful Event 48 – Rollover 49 – Rollover Initiation Type 50 – Location of Rollover Initiation 54 – Fire Occurrence 55 – Origin of Fire
Crash Event Assessment	4 – Precrash Movement 5 – Critical Precrash Event 6 – Critical Reason for Critical Event 7 – Attempted Avoidance Maneuver 10 – Crash Type
Investigator’s Description of Crash
Driver/Surrogate Description of Crash Event
Crash Diagram

 

In order to support the development of EDR data element tiers, individual LTCCS cases were examined to determine what data would provide information that could lead to the reconstruction of each crash with a high degree of confidence. The cases included information on the environment, driver actions, and vehicle kinematics that may have caused or contributed to the crashes. While many of the data elements included on the list are readily available on existing vehicles and may be acquired by a number of different means, some data elements are not readily available on all large trucks. For example, vehicle speed may be acquired through a number of different means depending on the equipment on the vehicle, which may include:

·        Read-out of vehicle speed sensor

·        Acquisition of speed from Global Positioning System (GPS) data

·        Calculation of speed from vehicle engine speed, gear engaged, and vehicle weight

Other situations exist where the technology is well established and referenced directly. Each manufacturer may use different means of acquiring the specific data elements. Also, the accuracy of the data from data sources may be questionable depending on its use. For instance, GPS provides information as it pertains to the receiver’s antenna as it moves under the GPS satellites. Concerning GPS-received heading data, it may be erroneously equated to vehicle heading. The GPS provides the heading of the antenna, which may not be the direction of the vehicle. This situation is most prevalent when there are big slip angles, as found in a sliding turn or spin-out.

The summation of the data from the analysis of the entire population of cases provided a listing of the frequency that a specific data element occurred in the accident reports for the reconstruction of the 133 crash cases. A total of 45 data elements were identified in this analysis. The occurrence in the summed data ranged from 100% to 0.8%. Table 17 lists the data elements in decreasing order of their occurrence in the cases.

There was a drop-off in the data element frequency after the first nine data elements. The remaining data elements have lower frequency of occurrence values, since this information would be needed to define specific crashes. The initial set of nine data elements would primarily be used to describe the initial conditions of the vehicle before the crash (vehicle speed, path, heading), the actions of the driver (throttle, brake, steering position history) and the vehicle kinematics during the crash (lateral, longitudinal tractor accelerations). The tenth data element in the list was video imaging in front of the truck cab, which may be useful for the detection of by the other vehicles involved in a crash.

Important information about the assessment of the data elements is summarized below:

·        A time standard by which all data can be linked is critically important in an EDR. The established time standard allows the construction of a crash timeline during the crash reconstruction effort.

·        Two data elements that could be provided by onboard safety systems include vehicle headway from Forward Collision Warning Systems (FCWS) and lane position from Lane Departure Warning Systems (LDWS). These technologies would not be available on all large trucks.

·        While video imaging from the front of the vehicle was high on the listing of data elements, the imaging of other aspects did not appear high in the listing.

·        Many of the elements that are easily accessible on the vehicle data bus were not high on the priority listing developed in this task. Also, “conventional” data such as headlight status, engine speed, and transmission gear engaged could be easily obtained.

·        While tractor acceleration appears on a high percentage of cases, trailer acceleration does not. This is primarily due to the dynamics of combination vehicles and the crash types; the acceleration of the trailer is primarily important in cases where the driver loses control, or the vehicle jackknifes. In other situations, the dynamics and acceleration of the combined tractor and trailer are essentially the same.

·        The data elements listed in Table 17 were based on engineering judgment in analyzing the LTCCS data to determine which data elements would have been useful in reconstructing each crash in the set of 133 crashes.

 

Table 17
Data Elements and Frequency of Occurrence in LTCCS Case Analysis