[author: Richard Robertson]

Introduction

Crash reconstruction is the application of scientific principles to determine what occurred in a collision or other claim. Accident reconstructionists provide their findings to insurance companies or to lawyers eventually providing expert testimony at trial.

Whether the incident involves a serious injury or is suspected to be fraudulent, the basis of the analysis is always evidence from the incident. This will always include physical evidence such as scene measurements from the crash scene (tire marks, gouges, fluid stains) or physical evidence from the involved vehicles (crush, seatbelt loading marks, scratches, and scuffs). However, more often the electronic data from the involved vehicles is an important source of evidence of what occurred.

Modern vehicles have several data networks, with electronic control units (ECUs) being the nodes on those networks. Each of these ECUs could be a source of electronic vehicle evidence which can be accessed for clues about what occurred in an incident.

Diagnostic Trouble Codes

Fault codes can be generated when a component breaks, its wiring is severed, or even if an unusual signal is detected. Any of these things may occur in a collision. We can use a diagnostic scan tool to interrogate many of the ECUs in a vehicle to get a list of detected faults. In some vehicles, the fault codes are accompanied by freeze frame data which records the state of the vehicle when the fault was detected. These data may include vehicle speed, engine RPM, and the odometer reading or even date and time when the fault was detected. Any of this evidence could be useful in a crash reconstruction or fraud investigation.

Event Data Recorders

A secondary function of some ECUs, such as the airbag control module, is to record a time-sequence of data associated with an event such as an airbag deployment or sudden jarring insufficient to deploy airbags. As such, these ECUs are often referred to as a “black box .” Reconstruction specialists have special tools and software to download and interpret this data. The retrieved electronic data will typically tell us how the vehicle was operated leading up to a collision including accelerator and brake pedal application, steering input, vehicle speed, and seatbelt use.

Infotainment and Telematic Systems

Most useful in fraud and theft cases, the electronic data contained in the infotainment system of a vehicle can be useful to a reconstruction specialist. Connected phones and call logs may point to who was operating the vehicle when it was reported stolen. Contact lists can be reviewed to determine if the involved parties knew each other. Some supported infotainment systems record a series of dates, times, and locations which show where and when a vehicle was driven.

Telematic systems may have data (typically location information) which can be downloaded from ECUs in the vehicle such as an OnStar module. Alternatively, the telematic data may be obtained from the service/platform that received the data from the vehicle, such as a financing company’s aftermarket tracker, or a bus or trucking company’s fleet management system.

Built-In Cameras

Most modern vehicles have built-in cameras. These are typically used to help the driver whether for lane keeping, forward collision avoidance, or back-up assistance. Some vehicles will retain images when an incident occurs. The events which trigger the storing of images vary by vehicle also. For vehicles for which our team has recovered images, we have used the images to aid in assessing pedestrian collision scenarios and to determine traffic signal colour. Such information can be useful in human factors analyses such as avoidance.

Other Modules and Vehicle Types

In some vehicles the powertrain control module (PCM) or engine control module (ECM) may hold useful data such as vehicle speeds. In many heavy trucks and buses, the ECM keeps data associated with sudden deceleration (or hard braking) events. Some makes of motorcycles have electronic data that can be recovered. Even off-road vehicles such as ATVs, snow machines, and personal watercraft may record useful incident-related electronic evidence. Some vehicles store information in their key fobs. Such electronic data may include the date, time, and odometer reading when the key was last used. This could be invaluable in a theft investigation.

If a vehicle is being driven following an incident, much of this electronic data could be overwritten. Therefore it is important for a reconstruction specialist to preserve all the evidence—both physical and electronic—which may be needed.

Acknowledgments

We would like to thank Richard Robertson for providing insight and expertise that greatly assisted this research.