Automobile and Heavy Truck Event Data Recorders

WDC Journal Edition: Spring 2008
By: Daniel Fittanto - Exponent – Failure Analysis Associates


For more than a decade certain cars and trucks have had the capability to record electronic data that potentially could be useful in the investigation and reconstruction of vehicle accidents. These vehicles have modules that, as a secondary function, may store data related to a pre-defined incident such as hard braking or impact and are generally referred to as Event Data Recorders (EDRs). The modules generally have a primary function related to engine control or air bag deployment. The secondary EDR function is intended to assist with system evaluations or diagnostics. The data can be extracted by trained individuals using commercially available equipment, and can be a useful, even critical, piece of the puzzle when reconstructing a vehicle accident.

Due to evolving technology, more Federal regulation and greater acceptance of the EDR technology, an increasing number of vehicles on the road will have retrievable data after a crash. Moreover, the amount of data recorded by vehicles is expanding. Impact severity, seat belt use, pre-impact vehicle speed, engine RPMs, percent throttle and brake pedal activation are common data available in automobiles today. Many heavy trucks can record vehicle speed, engine RPMs, engine load, cruise control activation, clutch application and brake application among other data prior to and after a significant deceleration. While these are the data sets most commonly used in accident investigations, there is additional data within these vehicles from which significant information about an incident can be gleaned.


Accident-related data in cars and light trucks can be stored in either or both the airbag control module (ACM), and the powertrain control module (PCM). Some General Motors vehicles extending back to model year 1994 have had data recording capability built into their airbag control module. In 2000, ACM data first became retrievable by police and vehicle engineers utilizing commercially available equipment, called the Collision Data Retrieval (CDR) system by Vetronix. In 2006 a division of Vetronix merged with Bosch, who now sells and supports the CDR system [1]. In late 2007, upgrades to the CDR system made PCM data retrievable on select vehicles [2].

General Motors
When the CDR system was initially released in 2000, the retrievable data was limited to certain General Motors vehicles equipped with electronic airbag control modules. Starting in Model Year 1994, select vehicles were capable of recording data related to the impact phase. This data generally included a plot of the vehicle speed change (delta-V) during the impact, driver seat belt status and other data surrounding the impact. Starting in Model Year 1999, an certain vehicles equipped with newer modules could record pre-impact data for up to 5 seconds prior to impact, including vehicle speed, percent throttle, engine RPM and brake on/off condition. Recently the data retrievable from some General Motors vehicles has been expanded to include information related to anti-lock brakes, vehicle stability control (VSC) systems, side and head-curtain airbags and anti-rollover technology [3].

Data from Ford vehicles became available in 2002 and extends back to a limited number of Model Year 2001 vehicles. This data was related to the impact phase and provided graphs of vehicle acceleration, delta-V and information on occupant restraints. In late 2007 new CDR technology became available to retrieve pre- and post-impact data, including (but not limited to) vehicle speed, percent throttle, and brake on/of condition from select Ford vehicles [4]. The pre and post-impact data from these Ford vehicles is stored in the powertrain control module (PCM), and not the air bag control module. PCM data can be more volatile than the ACM data and care must be taken to properly access this data to avoid spoliation issues. Impact-related data for Ford vehicles is still contained within the ACM, thus data from a Ford vehicle may need to be obtained from two separate modules.

In late 2007 new CDR advancements enabled the retrieval of data from some Chrysler vehicles dating back to model year 2004. Chrysler data is downloaded from the ACM, and contains only pre-impact data such as vehicle speed and other information on the vehicle operation for 2 seconds. At this time, data related to the impact severity is not available [5].

Other Manufacturers
Isuzu has two models with limited coverage that contain data similar to some GM models. One Mitsubishi model is currently covered with data similar to some Chrysler models. Suzuki currently has one model covered with data similar to some GM models [6].

Federal Rule 49 CFR Part 563

Federal Rule 49 CFR Part 563 requires that for cars and light trucks manufactured after September 1, 2010 and equipped with an EDR, specific data be recorded, and that the data be retrievable and readable in a specific format using commercially available technology. Select data is required to pass a survivability test, and the EDR capability must be published in the owner’s manual with specified language [7]. There have been petitions to this law, but as it currently stands there could be a large increase in vehicle coverage beginning with Model Year 2011 vehicles.

Heavy Trucks

Heavy trucks potentially have several sources of stored data related to an accident. Data may be recorded in on-board original equipment manufacturer (OEM) modules, aftermarket devices or satellite based and remotely stored.

Electronic Control Modules
By far the most ubiquitous EDR on heavy trucks is the electronic control module (ECM), sometimes referred to as the engine control module. Every engine today has an ECM, the primary function of which is to control the engine’s performance, fuel efficiency and emissions, to safeguard the engine, to allow technicians to modify the operation of the engine and troubleshoot mechanical problems, and to monitor the operation of the vehicle. Additionally, ECMs may contain data related to an accident event.

Unlike automobile EDRs, truck ECMs do not record data related to air bag deployments or near-deployments, but several engine models have the ability to record data surrounding a hard braking event by the truck. Each type of engine refers to these events by a different name such as Hard Brake, Quick Stop, Sudden Deceleration and Incident. Typical data recorded around these events include vehicle speed, engine RPMs, brake on/of condition, throttle amount, cruise on/off condition, clutch engaged yes/no and engine load, although the available data varies by manufacturer. The level of deceleration required to trigger an event can be programmed within the ECM, including turning off the ability to record data related these braking events.

In addition to hard brake data, a heavy truck ECM may record vehicle operation data around an engine fault code that can be set during the course of an accident. The type of data that can be recorded depends on the manufacturer, but may include vehicle speed, engine RPMs, brake on/of condition, throttle amount, cruise on/off condition, clutch engaged yes/no and engine load as well as various other vehicle operation parameters. The amount of time for which this data can be recorded relative to the setting of the fault code can range from a single data point to 55 seconds.

Finally, there is additional data within an ECM that can be useful. For example, the engine configuration data, although not incident-related, can provide useful information regarding the vehicle at the time of the accident such as the engine horsepower, programmed transmission and axle ratios, and governed engine speed.

Detroit Diesel
Detroit Diesel and Mercedes Benz (MBE) engines equipped with a DDEC IV or later ECM contains Hard Brake events. Up to two such events are stored and they contain 60 seconds of data before the Hard Brake and 15 seconds after recorded at 1-second resolution. Detroit Diesel engines also contain data related to the Last Stop event for the vehicle, which is the last time the vehicle was brought to a stop. The Last Stop event records similar data as a Hard Brake event, except the Last Stop event encompasses 105 seconds before the stop and 15 seconds after. The Last Stop data is not locked and will be overwritten if the vehicle is driven again.

Detroit Diesel ECMs prior to the DDEC IV may contain Hard Brake data if the vehicle was equipped with an optional in-cab recorder called a Pro Driver.

Detroit Diesel engines may also contain data related to an engine fault code. This data includes, but is not limited to, vehicle speed for 55 seconds prior to the setting of the fault code at 5-second resolution [8].

Caterpillar ECMs can record up to four Quick Stop events. A Quick Stop contains 44 seconds of data before an event and 15 seconds after recorded at 1-second resolution. Historically, Caterpillar ECMs have had a default setting for this deceleration threshold that would turn the EDR function off and not record a Quick Stop. The default setting can be reprogrammed by a Caterpillar dealership, or an engine technician equipped with Caterpillar software.

Caterpillar ECMs may also record a Snapshot related to some critical engine fault codes. This Snapshot may contain approximately 12.5 seconds of data recorded at 0.48-second resolution and includes vehicle speed, engine RPMs, brake on/of condition, throttle amount, cruise on/off condition, clutch engaged yes/no and engine load and various other vehicle operation parameters [9].

Current Cummins ECMs can record up to three Sudden Deceleration events. A Sudden Deceleration event contains 59 seconds of data before and event and 15 seconds after recorded at 1.0 seconds resolution.

Cummins ECMs may contain information on vehicle speed and other parameters for a single data point surrounding an engine fault code [10].

Older vehicles with Cummins engines may contain Panic Stop data if they were equipped with an optional in-cab device called a Road Relay.

Mack ECMs can record up to two Incident events. The number of data points that can be stored is 160, but the duration for the data varies depending on the user-defined resolution setting. At 1.0 seconds of resolution an Incident contains 80 seconds of data before the event and 80 seconds after. At 0.2 seconds of resolution an Incident contains 16 seconds of data before the event and 16 seconds after [11].

Volvo and International
Volvo and International ECMs do not currently contain data related to a hard stop event. Volvo ECMs may contain limited data around engine fault codes, but International ECMs do not. These ECMs do contain data regarding the engine configuration.

Other Truck EDRs
Electronic ‘tachometers’ are one type of commercially available aftermarket device that can record information on how a vehicle has been driven such as vehicle speed, engine RPMs, and heavy braking events [12]. Use of these devices is not prevalent in the United States.

Another type of aftermarket device is a collision warning system. The Eaton-VORAD System is an in-cab device that emits low power, high frequency radar signals to detect vehicles surrounding the truck, and gives audible and visible warnings when vehicles are closing at specified rates. If a vehicle equipped with such a device is involved in a collision, the VORAD module can be sent to the manufacturer and the data extracted. A report on the data will also be provided by the manufacturer [13].

Many truck fleets are monitored by satellite based communications and tracking systems for logistical purposes. Qualcomm and Xata are two providers of such services. An available product through the satellite communication providers is an incident-related service that records data related to a specified event such as a hard brake by the truck. When this service is provided, the data is monitored and recorded remotely [14], [15].

Freightliner manufactures and sells with some of its trucks a computer known as a Data Logging Unit (DLU). Its primary purpose is diagnostics of difficult problems, and it logs an event when a sensor exceeds set limits. When an event occurs the unit can store information before and after the event [16].

Imaging of the EDR data from automobiles or heavy trucks requires cables designed to connect to the vehicle’s diagnostic port or directly to the module in which the data is stored, along with a translator device and a laptop computer. Currently Bosch’s CDR system is required to extract data from automobiles [17]. For heavy trucks, each engine requires equipment and software specific to the make of engine [18].

Data can be obtained while the modules are still on the vehicle, or after the modules have been removed. Each type of EDR has specific issues related to the potential loss of data that must be considered during the extraction process. The condition of the vehicle post-accident typically dictates exactly how the data is best retrieved.

Legal Access

The laws regarding the ownership and permission requirements for obtaining EDR data vary from state to state and are evolving. The position of NHTSA is that the owner of the vehicle is the owner of the data collected from an EDR [19]. Therefore, the accident reconstructionist will typically depend upon the attorney’s guidance as to the requirements to legally image the data in their jurisdiction. It is also important that there be communication between the accident reconstructionist and counsel regarding the data extraction process and any associated inherent risks.

Use of Data

EDR data can be a valuable piece of the accident reconstruction puzzle. However, the data can sometimes be misleading or simply unreliable. When using EDR data, the reconstructionist must answer some critical questions: Does the data correspond to the subject accident? Is the data reliable? How exactly does the data fit into the accident? To answer these questions, the EDR data must be reviewed in conjunction with, but not in place of, the physical evidence.

For example, if an automobile is spinning prior to impact, the vehicle speed recorded in the ACM or PCM during that time may not accurately reflect the speed of the vehicle as it slides across the roadway. The task of the reconstructionist is to correlate the recorded data to the accident sequence through analysis of the physical evidence. Another example where recorded speed may differ from actual speed, depending on when the timing of the data, is in a vehicle rollover situation.

In a heavy truck example, if the tractor jackknifes and as result is pushed sideways down the road by the trailer, the vehicle speed recorded in the truck engine ECM during the jackknife phase of the accident will not accurately reflect the actual speed of the truck. By examining the physical evidence with respect to the vehicles and the accident scene, a reconstructionist can determine what portion of the ECM data does reflect the actual movement of the tractor and thus correctly utilize the ECM data. Even during a straight-line hard braking event, it has been demonstrated through testing that there is a difference in the ECM recorded vehicle speed (which records wheel speed based on driveshaft RPMs) and the actual speed of the vehicle [20].


Many automobiles and heavy trucks today have electronic data that may be useful to the investigation and reconstruction of vehicle accidents. When downloaded properly and reviewed in conjunction with the physical evidence by experienced individuals, this data can be an important piece to the accident puzzle.


[2] CDR Vehicle List—Version 3.0 by Bosch

[3] CDR Version 3.0 Help File—Supported GM Vehicles

[4] CDR Version 3.0 Help File—Supported Ford Vehicles

[5] CDR Version 3.0 Help File—Supported Chrysler Vehicles

[6] CDR Version 3.0 Help File—Supported Isuzu, Mitsubishi, Suzuki Vehicles

[7] 49 CFR Part 563

[8] DDEC Reports Software

[9] Caterpillar ET Software

[10] Cummins Powerspec and Insite Software

[11] VMAC Software






[17] CDR Version 3.0 Help File

[18] Preserving Data from Electronic Control Modules on Heavy Duty Truck Engines for Accident Investigation, Sebastian A.B. van Nooten, P.Eng. and James R. Hrycay, M.A.Sc., P.Eng., HRYCAY Consulting Engineers Inc., 2004


[20] Ruest TJ, Morgan JM. “Commercial Vehicle Event Data Recorders and the Effect of ABS