The result is that the EDR is now being re-engineered by the NHTSA and other interested parties to meet operational and reporting standards for a broader audience—although these parameters will apply only to automakers who install EDR modules in their airbag systems, with voluntary compliance set for 2010. To be clear, not all cars have EDR modules in their airbag control systems—the NHTSA estimates 64% of model year 2005 have some EDR capability. Those numbers certainly will increase over time, but at this point it is an automaker’s decision whether or not to install EDR.

What is the EDR?
The EDR is a box of circuitry attached to the airbag module that will collect operational information if the airbag deploys. An important detail: there are crashes and near crashes in airbag lingo. The airbag deployment module activates when it suspects an accident is in the offing, and that is known as a “near crash.” The system is ready to react, but the airbag does not deploy. The EDR will store near-crash data until it’s overwritten by another near-crash or crash event. It’s the crash event that is significant here—that’s the data accident investigators will harvest.

What turns on the airbag deployment system? Sudden changes in speed. When rapid accelerations or decelerations occur, the EDR system wakes up and does two things. First, the EDR takes the data it has been sampling every second and saves the last five seconds of it. This data includes vehicle speed and engine RPM, and also may include seatbelt buckling, brake application, shifter position, cruise control settings, and throttle setting. Secondly, the EDR records the subsequent rapid changes in vehicle speed which describe the behavior of the vehicle during the collision. This second type of data sampling may occur for a fixed amount of time, or it may continue until the system determines that the action has ended.

How is data collected?
If the vehicle has an EDR, then its crash data can be downloaded by using a Crash Data Retrieval (CDR) interface. The only commercially available system comes from Vetronix Inc., a wholly owned subsidiary of Robert Bosch GmBH, and licensed by General Motors (GM), Ford and Chrysler. Some joint venture vehicle lines like Isuzu (GM) and Volvo (Ford) also are compatible, but it’s important to know that, even with these automakers, not all models can be accessed through the Vetronix CDR. EDR access for all other automaker models must be initiated through the manufacturers, although they’ll now have to facilitate CDR access under the NHTSA rule. Most importantly, CDR downloads are best performed by those trained to operate the interfaces—this could be the automaker, law enforcement personnel, or auto accident investigators.