Airbag Control Module (ACM) Forensics
Car and light truck black boxes or Event Data Recorders (EDRs) were originally developed to assist car manufacturers and air bag systems manufacturers to control airbag deployment and to collect data at or about airbag deployment. Information from these devices may be collected after a crash and analyzed to help determine the status of the vehicle prior to the deployment of the airbag and for a few seconds after deployment of the airbag.
EDRs are made up of a tamper-proof device that writes the information it collects to electronic memory. The electronic memory usually stores only a few seconds worth of pre-crash and a few seconds of post-crash information. Some store much more information.
Most EDR systems are constantly collecting information from the various computers in the vehicle. EDRs are usually part of the Supplemental Restraint System (SRS). SRSs include the sensors that can detect impact or sudden deceleration and determine what restraint systems to deploy such as Airbags or Seatbelt pre-tensioners.
Different manufacturers record different information in their EDRs. The most common data elements are: whether or not the brakes were applied, the speed at the time of impact, how far the accelerator was depressed, the engine revolutions per minute, the steering angle, and whether seat belts were "Buckled" or "Unbuckled" at the time of the crash.
As these devices become more sophisticated, the amount of data collected increases. Newer EDRs collect information including: Longitudinal (Front to Back) and Lateral (Left to Right) Acceleration and Velocity change as well as Vertical (Up and Down) Acceleration and Roll Rates (Roll Over).
External transmission of some information can also occur. For example, General Motors' OnStar system currently transmits airbag deployment information along with the location of the vehicle in GPS coordinates. This transmission happens as long as the vehicle has the appropriate cell phone coverage.
The data downloaded from older EDRs usually contains several pages of information. Newer EDRs may include many more data elements and require more pages to report. The amount of data collected is dependent upon the make/model/year of the vehicle being evaluated.
Occasionally data cannot be recovered from an Event Data Recorder. Catastrophic electrical failure or shorts, fire or destruction of the unit may prevent the data from being read.
ESI has the knowledge, experience and technology for extracting and reporting black box data.