Value of Vehicle System Data in Accident Reconstruction

By Wesley VandiverAccident Reconstruction, , , ,

EDR Data: What Is and Is Not Included

The acquisition and analysis of electronic data during the investigation of automotive accidents has become commonplace. The availability of “crash data” has grown steadily since the late 1990s. Currently, the most common data retrieved by accident investigators is from devices known as event data recorders (EDRs). Although various definitions exist for an EDR, the NHTSA (National Highway Traffic Safety Administration) relies upon the following:

Since the term “EDR” can be used to cover many different types of devices, we believe it is important to define the term for purposes of this research site. When we use the term EDR in this site, we are referring to a device installed in a motor vehicle to record technical vehicle and occupant information for a brief period of time (seconds, not minutes) before, during and after a crash. For instance, EDRs may record (1) pre-crash vehicle dynamics and system status, (2) driver inputs, (3) vehicle crash signature, (4) restraint usage/deployment status, and (5) post-crash data such as the activation of an automatic collision notification (ACN) system. We are not using the term to include any type of device that either makes an audio or video record, or logs data such as hours of service for truck operators. EDRs are devices which record information related to an “event.” In the context of this site the event is defined as a highway vehicle crash.[1]

As this definition makes clear, EDR data is designed to be from a monitored “event.” For those familiar with EDR technology, we also know that per 49 CFR Part 563 – Event Data Recorders, there are specific parameters for what qualifies as an “event” that must be recorded. The following definitions are included within the statute[2]:

Event means a crash or other physical occurrence that causes the trigger threshold to be met or exceeded, or any non-reversible deployable restraint to be deployed, whichever occurs first.

Trigger Threshold means a change in vehicle velocity, in the longitudinal direction, that equals or exceeds 8 km/h within a 150 ms interval. For vehicles that record “delta-V, lateral,” trigger threshold means a change in vehicle velocity in either the longitudinal or lateral direction that equals or exceeds 8 km/h within a 150 ms interval.

The ability to acquire EDR data for use in analyzing how a collision occurred has been a tremendous breakthrough in the evolution of accident investigation. Currently, more than 20 manufacturers produce vehicles with accessible data. But what about those situations when there is no “event”, or when the “event” falls below the trigger threshold (e.g., low-speed collisions, impacts with pedestrians and bicyclists, etc.)? What if we are interested in whether or not the driver was actively texting or talking on his or her cell phone? EDRs do not record this information. During the investigation of many vehicular crimes, the mere presence of the vehicle at the scene can be an issue, such as in hit-and-run cases. EDRs do not record vehicle location.

Enter Infotainment and Telematics Systems

What if there were a way to acquire information from a vehicle that included not only its historical whereabouts, speed, and direction, but also synced devices, phone calls, and text messages? As a bonus, how about timestamps when doors were opened or closed, and when gear shifts were made? In fact, this information is currently available in many vehicles.

The acquisition of infotainment and telematics data is an emerging technology that has migrated from being strictly used in high-tech crime investigations and digital forensics labs to now being used in accident investigations. This technology is not in competition with systems used to acquire EDR data. The EDR systems will be necessary tools for the well-equipped accident investigator for the foreseeable future. However, the data acquired by EDR systems is generally only present under the aforementioned circumstances, and then generally only covers a period of time for an interval of approximately five seconds leading up to the event.

What if we wish to corroborate or refute the statement of a witness who reports to have observed the vehicle in question prior to the incident at a certain location, or traveling at a particular speed? What if we want data as to the whereabouts or speed of the vehicle yesterday, last week, or at some point hundreds of miles prior? That data may be recorded in the vehicle’s infotainment and telematics system, along with whether or not a particular person’s cell phone was used in the car, what calls were made, and/or what text messages were sent. In some instances, the actual audio recording of an occupant using the voice recognition system may be stored.

The above types of data cannot simply be obtained through a basic OBD-II port hookup and the press of a button, but iVe is a tool that facilitates the acquisition of data from many infotainment and telematics systems.


The following map with annotations shows a segment of highway along which there was an alleged pedestrian hit-and-run collision. Each blue dot is a trackpoint recorded by the vehicle. Each trackpoint contains GPS coordinates, date, time, and vehicle speed. The trackpoints are recorded by this vehicle at 1Hz (once per second). Most importantly, it should be noted that this data is constantly recorded regardless of an event.

The following velocity log covers the same time period shown above in the map. This is velocity log data taken directly from the CAN bus showing wheel speed sensor data. Yes, the vehicle in this example reports both GPS-derived speed and actual wheel speeds. Those familiar with this type of data will realize that there are circumstances that can affect the accuracy of both GPS data and wheel speed data. Having both for corroboration can be extremely helpful during an investigation. Again, as noted before, this data is constantly recorded regardless of an event.

In the next blog entry we will focus on the accuracy of data acquired by iVe as determined by testing and validation.

[1] National Highway Traffic Safety Administration,

[2] U.S. Government Publishing Office,

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