Event Data Recorders: Black Box data sources in automobiles and trucks

Event Data Recorders: Black Box data sources in automobiles and trucks David J. King, PE Passenger vehicles and heavy duty trucks may electronically record valuable information when involved in a collision. The author discusses potential data sources, their contents and how the data can be used in litigation and accident reconstruction. After an airplane crash, you often hear news reports about federal investigators examining the black box or flight data recorder. Such electronic data can be critical in reconstructing the accident. Similarly, most automobiles and trucks have on-board devices that record information about a crash. When it comes to motor vehicle collisions, lawyers should be aware of the various electronic modules that may record data, what data they contain and how it can be used. In discussing this topic, the data sources for passenger vehicles (cars, trucks, vans and SUVs) are presented separately from heavy-duty trucks (tractortrailers, dump trucks, etc.) because they differ in operation and data content. The method of applying electronic data recordings to an accident reconstruction, however, remains the same. A black box is the colloquial term for an event data recorder (EDR). As their name implies, EDRs are normally activated by a collision or rapid deceleration. The National Highway Traffic Safety Administration (NHTSA) defines an EDR as a function or device installed in a motor vehicle to record technical vehicle and occupant information for a brief period of time before, during and after a crash for the purpose of monitoring and assessing vehicle safety system performance. The type of information recorded and duration of the recording depends on the EDR source. Passenger vehicle EDRs are usually part of the airbag control module, a small box normally located in the occupant compartment, somewhere along the center tunnel or under the front seats (Figure 1). Early EDRs, introduced in the mid-1990s, recorded limited information, but the technology has evolved rapidly. Nearly all new passenger vehicles have some form of EDR and may record pre-crash details such as wheel speed, engine speed, throttle position, brake application, steering wheel position, occupant presence, seatbelt usage and even outside air temperature (Figure 2). Whether or not this information can be retrieved is another story. Data from most GM, Ford and some new Chrysler vehicles Figure 1 Exemplar airbag control module. Figure 2 Passenger vehicle EDR overview. MEA Forensic Engineers & Scientists Inc www.meaforensic.com

is accessible using publicly available, albeit specialized, electronic tools. Data from other vehicles is presently only accessible by the manufacturer and data retrieval has been limited in many cases. With the accessibility and type of EDR data varying between vehicle makes and models, the NHTSA has introduced new rules (49 CFR 563) to standardize the recorded parameters, minimum wake up or activation thresholds and access to EDR data for passenger vehicles weighing less than 8,500 lb. The new rules will apply starting with model year 2013 vehicles and also require the manufacturers to make the necessary access tools and software available to the public. EDRs are not just limited to airbag control modules, although they are the most common source. Modern vehicles have a multitude of independent electronic control modules all linked together by the vehicle computer network. These controllers may include the engine or powertrain control module (ECM or PCM), anti-lock brake systems (ABS), electronic stability or traction control (ESC or ETC), heavyduty auto-shift transmissions, collision avoidance systems and GPS based tracking systems. The ability of these modules to record useful collision information depends on the device. Regardless of the acronym used, electronic data sources may exist in your case. It is important to use an appropriately qualified expert as soon as possible to determine what data sources are available and prevent the loss of volatile electronic evidence. Case Study #1 Liability Shift: At an intersection, a driver turned left in front of an oncoming vehicle resulting in a collision. The impact location and vehicle rest positions were documented, but there were no tire marks on the road because it was a rainy day. A traditional accident reconstruction concluded that the straight through vehicle was traveling near the speed limit at impact. Based only on this information, the left turner would be found to have violated the through vehicle s right of way. The EDR data confirmed the impact speed calculated using traditional methods. However, it also indicated the oncoming vehicle was traveling nearly twice the speed limit about 3 seconds before the crash and then braked heavily, reducing its speed at impact to near the posted limit of 30 mph, as shown in Table 1. Had the driver been traveling at the speed limit, the collision would not have occurred. The jury found the driver of the speeding through vehicle was primarily liable for the crash. When is data recorded? Supplemental restraint (airbag and seatbelt pretensioner) controllers generally monitor for frontal collisions and sometimes lateral collisions in vehicles equipped with side airbags. When these controllers measure accelerations greater than a preset threshold, they will activate or wake up in preparation for a possible deployment. If the controller decides the collision is sufficiently severe, the supplemental restraints are deployed. If the collision is not severe enough, there is no deployment. In both cases, the decision as to whether or not the collision is a deployment or non-deployment event is made within tens of milliseconds far less than the blink of an eye. Both event types usually activate the EDR function within the airbag module so it records information. Many EDRs are also capable of recording more than one event so it is not unusual to have both a deployment and nondeployment event recorded after a severe collision. If the collision pulse is less than the threshold to wake-up or is in a direction not monitored by the airbag module, no collision data is recorded. In most cases, heavy braking and rearend impacts do not result in event data being recorded, but occasionally it happens. Sometimes, data is even present in lateral collisions because the frontal component of the collision deceleration exceeds the EDR s wake-up threshold. After an airbag deployment, the EDR will permanently lock any data in memory and it cannot be overwritten. Generally, the airbag control module is a single use item so it is replaced if the Table 1 Pre-impact vehicle speed and braking data for case study #1. MEA Forensic Engineers & Scientists Inc www.meaforensic.com

Table 1a Pre-Crash data vehicle is repaired. In cases involving airbag deployment, the data may be uploaded and saved for later analysis. Alternatively, the actual airbag control module may be physically removed and preserved as evidence for any legal proceedings as it is no longer a useful part of the vehicle. If the vehicle is repaired before the data is accessed, repair shops will usually dispose of the modules and evidence will be lost. In the case of a non-deployment event, collision data is not stored permanently and it may be erased or overwritten. How and when the event is over-written is manufacturer dependent, but generally results after a subsequent collision event or a preset number of ignition cycles. Therefore, in cases involving minor collisions where the airbags have not deployed, there still may be data available, but it should be accessed as soon as possible. EDR data depends on the source Information recorded by an EDR depends on the vehicle manufacturer, model year and even vehicle options. Modern EDRs are connected with the vehicle s controller network, much like the wires connecting a network of computers in an office. Information is transmitted over the network from different locations and recorded by the EDR. For example, engine speed and throttle position are monitored by the engine controller, and this information is sent over the network to the EDR. Other information may be directly wired to and monitored by the EDR. Such information may include the seatbelt engagement switch in the buckle, occupant detection in the seat cushion and airbag status. As the recording capability varies, EDRs should be considered on a case-bycase basis to see what they may contain. A complete list of supported passenger vehicles is provided by Bosch (www. boschdiagnostics.com/testequipment/ cdr), the manufacturer of the crash data retrieval software for supported passenger vehicles. An abbreviated summary of potential data sources for passenger vehicles is listed in Table 2. General Motors The airbag controllers from GM products are known as sensing and diagnostic modules (SDMs) and can be downloaded as far back as the 1994 model year. The early generation SDMs recorded a small amount of data and nothing prior to the collision. They recorded collision severity in terms of speed change as well as driver seatbelt use, the number of system fault codes present and various system status parameters. As the modules evolved, they began to record information about the right front occupant and even the rear seats in some minivans. Starting in the 1999 model year, SDM recordings began to include data Table 2 Abbreviated summary of passenger vehicle EDR sources. (Described data may not be available for all makes/models.) MEA Forensic Engineers & Scientists Inc www.meaforensic.com

for five seconds before the collision. The pre-crash data is recorded about once every second and includes vehicle speed, engine speed, throttle position and brake switch status. This data can provide the investigator with knowledge of what the vehicle and driver were doing leading up to the collision. The quantity of pre-crash data has increased and now includes parameters such as steering wheel angle, cruise control settings and even outside air temperature. Ford Ford vehicles can contain EDR data in the airbag controller, known as a restraint control module (RCM), and within the powertrain control module (PCM) on specific vehicles. The crash data within the RCMs is available for select 2001 model year and newer vehicles. The Ford RCM records the acceleration pulse and reports collision severity in terms of speed change. Precrash data is available on newer models, but not older ones. The driver s seatbelt status and a variety of system status parameters are also recorded. Starting in the 2003 model year, select Ford vehicles began using PCMs that record pre-crash data. The PCM stores 25 seconds of pre-crash data including parameters like vehicle speed, braking, throttle position, engine speed and more. Data is recorded at a frequency of 5 Hz, or five samples per second. The only issue with this data is that the PCM is not a dedicated event data recorder, so recording is not tied to a collision event and sampling is continuous. A deployment event may lock the PCM data, but after a non-deployment event the PCM data will be overwritten when the ignition switch is turned to the on position. There is more pre-crash data available in the Ford PCM than there is from the GM SDM, but the data is extremely volatile and needs to be accessed immediately to guarantee it is not overwritten. Daimler-Chrysler Data from the Daimler-Chrysler airbag control module, known as the Occupant Restraint Controller (ORC), first became accessible on the 2004 Dodge Durango. In 2007, access was expanded to other vehicle models. Generally, these modules are capable of capturing pre-crash data as a result of a frontal impact severe enough to deploy the airbag. The ACM will record longitudinal acceleration data and up to 5 seconds of pre-crash data sampled at 10 Hz, or 10 samples per second. The pre-crash data may include engine speed, vehicle speed, throttle position, pedal position, brake switch status, ABS status, cruise control status and electronic stability control status. Other vehicle makes Other manufacturers, such as Honda and Toyota, also have airbag controllers with EDR capability, but access to these modules has not yet been made public. The modules can only be accessed using the manufacturer s proprietary software. Since 2001, some Toyota modules contain the collision speed change and pre-crash data such as vehicle speed and brake application. However, Toyota will only access the data when it receives a written request from the NHTSA for its special crash investigations program or in response to a court order or search warrant from law enforcement. The Toyota EDR in the van involved in the recent death of Angels pitcher Nick Adenhart was recently downloaded for law enforcement. If you have an ongoing case involving a currently unsupported vehicle, it cannot hurt to retain the EDR module as evidence in hopes that access to the data may be possible in the future. Case Study #2 Statement Corroboration: A head-on collision occurred between a Ford pick-up and a Chevrolet pick-up on an un-paved country road. Air bags deployed in both vehicles. The Ford driver alleged he had stopped prior to impact and was struck by the rapidly moving Chevrolet. The Chevrolet driver alleged his vehicle was stopped. The Ford was still available, but the vehicle was not a supported vehicle for download of the RCM or PCM. The Chevrolet had already been salvaged, but was a vehicle for which the SDM could be downloaded. Fortunately, the vehicle was found at the salvage yard and the SDM was obtained (it could not be re-used due to the air bag deployment). The SDM download showed the Chevrolet speed at impact was 40 mph, consistent with the Ford driver s statement. Heavy trucks Generally, heavy trucks do not have airbags, although it is an option for some vehicles. Therefore, the EDR source and operation in heavy trucks is slightly different than for passenger vehicles with airbag controller based EDRs. Nearly all heavy trucks use diesel engines and increasingly stricter emissions regulations have meant that engine manufacturers have had to implement more complex controls. As a result, all modern truck engines use an electronic engine control module (ECM) that monitors engine and vehicle operating parameters. The primary function of the ECM is to control the engine, but it can also serve the secondary function of recording engine and vehicle information. The data recorded by an ECM is mostly used for vehicle diagnostics, maintenance and fleet management, but may also be used in accident investigation. The engine ECM is the first place to look for black box data on a heavy truck, although there may be other sources as well. The information recorded by an ECM depends primarily on the engine manufacturer, model, year, and owner selected features enabled within the ECM software (usually at the time of

purchase). The main source of EDR data is called a Hard Stop, Quick Stop or Sudden Deceleration report in which the ECM records data when a sudden change in wheel speed is detected, usually at a deceleration rate greater than about 0.3~0.4g. Wheel speed is actually a calculated value based on the tire circumference, rear axle ratio and measured driveshaft rotation speed. Such reports typically save information such as wheel speed, engine speed, throttle position, brake status, cruise control status and other parameters. Data is captured from both before and after the event, so it is possible to look at the conditions leading up to an event. Over one minute of data may be recorded. ECMs may retain more than one hard stop event (often the last two or three) and these events are identified by the vehicle mileage or total hours of engine operation at occurrence. In addition to hard stop data, ECMs record general trip information, fuel consumption, idle time, maintenance data and fault codes among other things. This information is of interest to vehicle owners and fleet managers, but may not be directly useful to accident investigators. An abbreviated summary of data sources for heavy trucks is listed in Table 3. Cummins Before 2005, only vehicles equipped with an optional Road Relay system would potentially record Sudden Deceleration events. Compared to the number of vehicles sold, relatively few vehicles have this option installed. All model year 2005 and newer ISM and Signature/ISX series diesel engines are set from the factory to record the last three Sudden Deceleration events. These events are triggered by hard braking or a sufficiently severe collision and record data from 60 seconds before and 15 seconds after the trigger signal. Data is recorded at 1 Hz, or once per second, and includes engine speed, vehicle speed, engine load, throttle, brake status and clutch status. Detroit Diesel Since 1998, heavy-duty Series 60 engine controllers record the last two hard brake events as well as the last stop. The hard brake record contains data from 60 seconds before and 15 seconds after the event. The last stop record saves 15 seconds of data after the vehicle comes to a complete stop and 104 seconds prior to stopping. Both records include engine speed, vehicle speed, engine load, throttle, brake status and clutch status logged at at 1 Hz, or once per second. It is important to note that the last stop information is volatile data and will be overwritten as soon as the truck is driven away. Therefore, in critical cases, the data must be retrieved immediately after the incident or the vehicle must be towed from the scene and the data retrieved before the vehicle runs again. Caterpillar Caterpillar engines have been capable of recording sudden deceleration data or quick stops since 1997, but only if the software feature was activated at the customers request. Few engines have this feature enabled. Starting in 2007, the quick stop recording feature was enabled for all engines at the factory. The quick stop report contains data for 45 seconds before and 15 seconds after the event. The Caterpillar modules also have a snapshot recorder that captures data for 9.5 seconds before and 3.5 seconds after sensing a critical engine fault. If the critical fault is a result of collision damage, the recorded data may relate to the crash. Mack In engines built after 1998, a sudden deceleration will trigger the recording of an incident report in which the recorded parameters and sampling rate may be pre-programmed by the user. The default factory setting for data is 16 seconds before and after the event, recorded every 0.2 seconds (5 Hz). The fleet management software to access the data is not commonly available and will erase the ECM data after a download, which presents evidence spoliation issues for the investigator. To circumvent this problem, the manufacturer or an approved facility Table 3 Abbreviated summary of heavy truck EDR sources.

can extract the data for a fee without erasing the ECM. Other engines Volvo engines built since 2007 are reported to have similar incident reports found in Mack engines. International engines do not have any reported EDR function, but basic engine information is stored in the ECM. Since 2003, Mercedes truck engines are reported to have similar information as Detroit Diesel engines. Other data sources Heavy trucks may also have other sources of useful electronic data that are not as well known as the engine control module. It is usually necessary to examine the vehicle to determine what data sources may be present. Antilock brake system (ABS) controllers and electronic stability control (ESC) systems can record information in the event of a malfunction. If collision damage results in a malfunction, information about the vehicle when the malfunction occurred may be available. Alternately, it could be important to know if a malfunction was a causal factor in an accident. Eaton VORAD is a collision warning system using radar to monitor the vehicle surroundings and warn drivers of collision risk. The system also records information such as vehicle speed and direction which can be useful in collision reconstruction. Telematics systems, a combination of wireless telecommunication and GPS, are used for fleet management and load tracking. There are various systems available, each possessing slightly different capabilities. The EDR function of these systems must usually be determined by working with the fleet owner. Data may not be stored on the vehicle, but rather on a central database. Case Study #3 Data Interpretation: A road crew was working on a snow Figure 3 Removing memory chips from a damaged EDR. covered mountain road that was restricted to single lane alternating traffic with a speed limit of 20 mph. A tractor trailer was descending the hill when a police car attempted a U-turn in front of the truck. The truck driver swerved to avoid the police car and struck a pedestrian. There was no physical evidence to determine the truck speed, but the driver said he was going 20 mph and the police officer said he did not observe the truck speeding. The flagging crew gave conflicting statements and the ECM showed the truck was traveling at 44 mph prior to the accident. Further examination of the ECM data and physical examination of the truck found that the actual rear axle drive ratio did not match the ECM programmed settings. Testing showed the ECM speed reading was off by 240%. Correcting for this error, the ECM data indicated the truck was actually traveling at 19 mph. Getting the data The publicly available equipment to access passenger vehicle EDRs is called the Crash Data Retrieval (CDR) system and is available from Bosch Diagnostics. The system includes cables, software and an interface module allowing a personal computer to communicate with the EDR module. Access to the data can be relatively straightforward or quite complex, depending on the physical condition of the vehicle and the wiring. If the vehicle is relatively intact, the CDR system may be connected to the vehicle communication network through a diagnostics port, usually located under the dash. The software will retrieve the data in a matter of minutes. If the vehicle wiring is compromised, the EDR module must be located and possibly removed from the vehicle. Data is retrieved by connecting directly to the module. In rare cases where the EDR module has been physically compromised, but the memory chip is intact, the memory chip can be transplanted into a replacement module and the data retrieved. In all cases, data retrieval should be conducted by appropriately qualified individuals using the current version of the CDR program.

The tools required to access heavy truck ECMs are publicly available, but are manufacturer specific. Investigators must possess both the tools and qualifications to access data and it is relatively expensive to maintain this for all engine makes. Dealerships usually have the tools to access heavy truck ECMs. However, service technicians will not likely have experience in forensic investigation so there may be a risk of evidence spoliation or not gathering enough information. Such concerns may be alleviated if a forensic investigator is present when the download is conducted by a service technician. More than just crash data must be downloaded from the vehicle. Investigators must also gather physical evidence and information from the vehicles and scene to validate the electronic data. Generally, the electronic data is used to corroborate an accident reconstruction. It can also provide valuable pre-crash data that offers a complete reconstruction. Case Study #4 EDR Memory Chip Transplant: On a country road with no independent witnesses, two vehicles collided at an intersection and burst into flames. The pickup driver, who had the rightof-way, stated he was traveling at the speed limit when the other vehicle drove in front of him without stopping. The airbag module from his pickup was severely damage in the fire and the data could not be downloaded by traditional means. However, the memory chips within the unit appeared intact. The memory chips from the damaged module were physically removed and installed on an equivalent undamaged module (Figure 3). The data was successfully downloaded and the chip replacement technique was validated independently. The data corroborated the driver s statement and the results from a traditional reconstruction method. Appropriate use EDRs actually record signals from a variety of electronic sensors on the vehicle and save the information in a digital format. The software used to access the data translates it to a readable form which must be interpreted by an analyst. It is important that the analyst be suitably qualified and aware of the intricacies of data measurement, recording and retrieval. The recorded data cannot always be taken a face value. The timing of the data recordings is not necessarily exact (Wilkinson et al., The Timing of Pre-Crash Data Recorded in General Motors Sensing and Diagnostic Modules, SAE 2006-01- 1397) and the reported collision severity can be significantly wrong for angled or long duration collisions. Pre-impact speeds can even be underreported by up to 30% when ABS braking is active. Expert knowledge is crucial when testimony is required because EDR information may be misleading if it is not interpreted correctly. If the data is shown to be reliable and can be corroborated with physical evidence, it is usually accepted by the courts. Depending on the data available and the case, EDR information can benefit a variety of issues such as liability, fraud, injury and seatbelt usage. Final remarks EDR technology has become a hot topic amid concerns of privacy violation. Vehicle manufacturers now disclose the presence of EDR s to consumers, usually in the vehicle owner s manual. Many states have enacted or are in the process of enacting laws regarding EDR technology. In California, section 9951 was added to the California Vehicle Code effective January 29, 2003. CVC section 9951 (a) requires manufacturers to disclose that a new motor vehicle sold or leased as of July 1, 2004 is equipped with one or more recording devices, commonly referred to as an event data recorder or sensing and diagnostic modules (SDM). GM has been doing this for years and Ford started this practice in 2001. Most of the definitions of the recording device do not apply to the SDM, RCM, or ORC, which makes CVC 9951 essentially meaningless for investigators and reconstructionists in California. When properly obtained, interpreted and presented, EDR information has been found to meet both the Frye and Daubert standards before the courts. There have been cases where data from an EDR has not been accepted or disregarded by the courts. In such cases, the judge found the expert did not properly understand where the electronic data came from or what factors could cause the data to be unreliable. These rulings did not preclude the use of electronic data in future cases. As it is for any analysis method or new technology, it is essential that experts understand how EDR information is measured, recorded and retrieved. Electronic data continues to become more common and usually corroborates the findings of traditional accident reconstruction. Sometimes the data provides insight not available with traditional accident reconstruction techniques. If you have a case that may involve EDR information, work with a qualified expert, find out what information may be available and get it as soon as possible. Sometimes the black box ends up being a silver bullet. David King is a licensed Professional Engineer in the state of California. He is a principal and senior engineer at MEA Forensic Engineers & Scientists, and heads the Transportation Group. His areas of specialization include severity assessment, vehicle speed analysis, crash data recorder download and interpretation, and night-time visibility.

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