By Brett Weltman, Mack Smith, and Jason Young
The collection of collision data from the Event Data Recorder (EDR) of cars and trucks, also known as the ‘black box’, has come a long way since its inception. It is now a standard component of collision investigation methods. In forensic collision reconstruction, black box data is now commonly accessible for all newly manufactured passenger cars, pickup trucks and SUVs.
Over the past two decades, there have been significant advances in both the quality and quantity of collision-related data recorded by EDRs. More importantly, the data is now accessible by the public. In September 2012, NHTSA’s (National Highway Traffic Safety Administration) new regulation regarding public accessibility of EDR data came into effect. As a result, all new passenger vehicles sold in North America must have publicly-downloadable EDRs. This new requirement has literally opened up the door for accessing EDR data in all future collision investigations.
Prior to the 2012 NHTSA rule, collision investigators had access to EDR software from only a select group of domestically manufactured vehicles. Practically speaking, this would often leave forensic investigators without any EDR data to analyze in a collision. For example, if both involved vehicles were imports. Before describing the relevance of the current advances in this technology, let’s take a brief look at the history of its development.
Before modern EDRs were utilized as part of the airbag system of a vehicle, ‘impact recorders’ were used in the 1960s and 1970s. They worked as electro-mechanical devices to measure the gravitational force applied to shipping container units. These recorders were used by the shipping industry to find methods of transport to reduce impact forces on shipped goods to reduce damage. These recorders were also used to research the nature of impact dynamics. Airplane black box recorders (which, incidentally, are also not black but orange) were also introduced as a standard in the airline industry in the 1960s to record pre-crash conditions and events.
Beginning in the early 1990s, EDRs were introduced in a select group of commercially-available automobiles and light trucks. These were manufactured by General Motors in conjunction with the airbag system. The original purpose of these EDRs was to monitor and record the functioning of the airbag system. It functioned a safeguard for investigating malfunctions. EDRs quickly became a core component of airbag systems in all vehicles. As such, every vehicle with an airbag also has an EDR. However, only GM provided access to the software used to download that data. All other manufacturers maintained proprietary control over their EDR download software.
In 2001, Ford followed suit and began providing public access to the EDR software in some of their vehicles. Chrysler followed in 2005. Nevertheless, the first few generations of airbag EDRs recorded only a limited amount of information.
In 2006, General Motors was involved in talks with the United States Congress. This was in an effort to place EDRs in vehicles from other automakers. The movement was successful, eventually resulting in the NHSTA ruling of September 2012. It stated that all production automobiles and trucks sold in North America after 2012 must have publically-accessible EDRs. The success of the congressional hearings also encouraged the development of more sophisticated EDRs. These record lateral accelerations, rollover accelerations, and multiple collision events. As such, any Police detachment or collision investigator who owns the EDR download hardware and software can download information recorded by vehicles involved in a collision or near-collision.
Since EDRs are a part of the airbag control system, the module is always monitoring vehicle accelerations. Consequently looking for signs of an impending collision. However, the EDR only begins recording that data if a collision or near-collision is sensed. When that occurs, the monitored data is saved to the EDR. All EDR designs are different, but in most cases a recorded ‘non-deployment’ event will be overwritten by subsequent ‘non-deployment’ or ‘deployment’ events. Deployment events, on the other hand, cannot typically be overwritten. Some EDR models will delete non-deployment data after a certain number of ignition cycles. In any event, it is critically important to download and preserve EDR evidence as soon as possible after a collision. Just like any other evidence in a case would be preserved.
The type of information recorded by a particular model of EDR will vary. The minimum amount of information typically recorded includes the change-in-velocity during impact and the driver seatbelt status (used or not-used). Most EDRs now record speed and throttle/accelerator/brake pedal position for 2.5 to 5.0 seconds prior to impact. The sophistication of information recorded will generally increase with the sophistication in the number and type of airbags provided; i.e. front, side, curtain, two-stage, etc. Fleet tractor-trailers often have data recorder settings installed. These record 60 seconds or more of speed and throttle/accelerator/brake pedal position prior to impact.
Retrieving data from an EDR does not provide an instant solution to collision reconstruction. The prime example of this is pre-impact speed data, measured from wheel axle rotation, which is unreliable in cases of spinning or airborne wheels. As stated on all EDR printouts, the recorded data must be assessed in conjunction with the other collision evidence to validate its reliability.
The privacy issue regarding who owns the EDR data after a collision is an ongoing debate best left to legislators. To the engineering expert, the EDR data is just another fingerprint of evidence imprinted upon a car during a collision. No different than the depth and profile of crush on the outside of the car which is available for measurement by all.
The efficacy of EDR data was put to the test by NHSTA following the 2009 Toyota ‘unintended acceleration’ issue. From 2009 to 2011, Toyota’s reputation was severely marred by allegations that electrical or mechanical components in their vehicles were causing unintended acceleration. The US government tasked NHTSA, with the aid of NASA scientists, to investigate those collisions. The EDR data was carefully reviewed, along with electrical testing of the vehicles. In all cases no engine faults or electrical faults were found. The EDR data clearly showed that the accelerator pedal was being depressed in all of those cases for some reason. Following those findings, the investigations shifted focus to “sticky” accelerator pedals and the floor mat design.
In summary, EDR data collection, once only used for overseas shipping and aircraft, is now a standard component of collision reconstruction investigation. It will continue to play an increasing role in the future of criminal and tort cases. As the amount and nature of the data being recorded increases with continuous improvements to airbag systems, the issue of evidence preservation for EDR data will be more important than ever. EDR data provides collision investigators information that, when validated by supporting evidence, offers a reliable “window” to the past regarding the circumstances of a collision in dispute.