Vetronix Crash Data Retrieval System

Recovering the Information Stored in the Automobile’s “Black Box”

Historical Perspective

Since the early 90’s, vehicle manufactures have equipped their vehicles with air bags. Some manufacturers use deployment sensors to measure accelerations during the crash. This measurement device is located in the Sensory and Diagnostic Module (SDM). The SDM measures the crash to determine whether to fire the air bags or not. The information is then recorded in the Event Data Recorder (EDR). Other sensors, such as the brake switch, gather information that is relayed to the EDR during an event.

Event Data Recorder (EDR)

General Motors has been recording this data since the early 1990’s. The data recorder, similar to an airplane’s “black box”, is typically located in the passenger compartment of an automobile. The EDR records information about the air bag system and other crash related data. This data recording is triggered by an air bag deployment and/or some near-deployment events. Recorded information can vary, but usually consists of recording pre-impact speed, braking behavior, seat belt usage and position of the throttle.

Since 1998, GM in cooperation with Vetronix and the National Highway Traffic Safety Administration (NHTSA) has agreed to assist in developing a unit to retrieve the data. Recently Vetronix released the Crash Data Retrieval (CDR) system and is certifying users.

At this time, approximately 95 % of GM vehicles use this system in which the data is retrievable. Currently some Ford vehicles RCM’s (Restraint Control Module) can be retrieved for analysis. Although this data may not be available on all vehicles, it will be most beneficial as another piece of evidence to evaluate in an accident reconstruction situation.

Air Bag Module - the SDM

Air Bag Module is the vehicle’s “computer” that controls whether or not the airbag deploys. It also records a variety of other important information that can be useful in many different instances.

What Data Will Be Recorded?

Depending on the vehicle some or all of the following data will be recorded and will be able to be downloaded.

Brake status (5 seconds before impact)
DV vs. time for frontal airbag deployment event
Engine spend (5 seconds prior to impact)
Ignition cycle count at event time
Ignition cycle count at investigation
Maximum DV for near-deployment event
Passenger’s airbag state (enabled/disabled)
SIR Warning Lamp status (or/off)
State of driver’s seat belt switch (on/off)
Throttle position (5 seconds before impact)
Time between near-deploy and deploy event
Time from vehicle impact to airbag deployment
Time from vehicle impact to time of maximum DV
Vehicle speed (5 seconds before impact)

Uses for the Information

There are many potential uses for this information such as:

Improve Vehicle Design/Highway Infrastructure
Provide a Basis for Regulatory & Consumer Information Initiative
Provide Objective Data for Crash Reconstruction
Develop an Objective Driver Behavior Database.

In accident reconstruction this information will assist the reconstructionist with the following information.

Pre Crash Data

Gives seconds of pre-crash data such as vehicle speed, engine speed, braking and percent throttle.

Crash Data - Delta V

During the crash, vehicle change in speed. This relates to crash severity. (Low speed and high speed)

Data Summary

Vehicle system status, warning lamp, drivers seat belt switch and impact time to air bag deployment time.

Benefits of the CDR:

Helps in the design of safer roadways
Assists traffic accident reconstructionists in their accuracy, reliability and understanding of a particular accident.
Validates crash reconstruction programs.
Illustrates how override effects collision severity.

Drawbacks of the CDR:

The SDM may not function to its full extent of capabilities as all the data may not of been recorded or downloadable.
Data may not be accurate
Limitations –

The CDR is another tool to assist the industry with determining the events during an accident. To determine whether your vehicle information can be read is as simple as checking the vehicle identification number.

The information gained from this process will not reconstruct an accident in and of itself. It serves as a valuable tool and resource that too should be given proper evaluation in an accident reconstruction situation.

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