Many cars and light trucks on the road today have the ability to store electronic data related to an impact. These so-called “black-box” data can be useful when analyzing and reconstructing an accident. Certain General Motors vehicles extending back to model year 1994 have data recording capability built into their airbag control modules that can be retrieved by investigators. Newer Ford and Chrysler vehicles also have modules that record impact data. Exponent’s vehicle engineers are trained and experienced in the secure and comprehensive retrieval of data from these modules using the Bosch Crash Data Retrieval (CDR) system.
Automobile CDR data are quite valuable in the analysis and reconstruction of a vehicle accident.
Under the new Federal Motor Vehicle Safety Standard 126, an increasing number of vehicles on the road will have the capability of recording crash-related data, and the amount and type of data recorded by these modules will be expanded. Data recorded by the modules include:
- Vehicle speed
- Delta-V
- Brake on/off
- Percent throttle
- Engine speed
- Seatbelt use
- Lateral acceleration
- Yaw rate
Retrieval of the data from these modules requires special equipment designed to read and image the stored data by connecting either to the vehicle’s diagnostic port or directly to the module. Vehicles on the road today can store accident-related data in several different modules, depending on the make, model, and year of the vehicle:
- Airbag Control Module (ACM)
- Rollover Sensor (ROS)
- Powertrain Control Module (PCM)
Data can be retrieved while the modules are still on the vehicle, or after they are removed, and the post-accident condition of the vehicle dictates which method will work best. In addition, each type of module has specific characteristics that may induce a loss of data during the imaging process.
Physical evidence is also important, and relying exclusively on the CDR data can lead to incorrect or unreliable conclusions. Understanding of the data acquisition process used by the on-board automotive network is also critical to avoid erroneous conclusions. When analyzing the CDR data, the accident reconstructionist must answer some crucial questions:
- Were the data actually recorded before/during the accident?
- Do the data appear to represent what we know of how the accident happened?
Exponent’s accident reconstruction engineers have the technical skill and specialized training required to integrate the physical evidence with the CDR data to produce a comprehensive and reliable vehicle accident reconstruction.