A Weighty Decision

In the increasingly complex world of vehicle accidents where multiple factors may be in play, traditional on-site visual examination, mechanical analysis and computer modeling may not be enough to bring clarity to the event. With the value of trucks and heavy vehicles being in the hundreds of thousands of dollars and their use directly related to the livelihood of the vehicle owner, there is a lot of pressure on adjusters and insurance companies to resolve these claims quickly and fairly.

Reviewing critical event data from on-board Electronic Control Modules (ECMs) of trucks and heavy equipment is a relatively new but increasingly important step in accident reconstructions that should aid in the resolution of claims. This article will explain how ECM data can assist investigators in their reconstruction.

A Little History

Sophisticated ECMs have been around since the early 1990’s and were originally intended to improve engine performance and allow information regarding the truck’s performance to be accessed by special software programs. ECM data continues to be used primarily by mechanics and fleet managers to troubleshoot mechanical failures in their trucks and maintain an efficient fleet operation. This leads to the first frustration for investigators trying to perform an accident reconstruction: the data recorded by ECMs was never intended for this purpose.

Electronic Control Modules in trucks are not the same as airplane ‘black boxes’ or airbag control modules and collision data recorders found on most modern-day automobiles. Unlike automobiles, major components of commercial trucks such as the engine, transmission and braking systems are often made by different manufacturers and use proprietary electronic controllers. Communicating on a network within the vehicle, each controller is responsible for the operation of its component and maintains its own event and fault records.

This aspect of truck ECMs leads to the second frustration for investigators: the amount of information that might be useful in a collision reconstruction varies greatly from controller to controller and thus from truck manufacturer to truck manufacturer. Compounding this frustration is the resulting lack of a universal software tool for accessing data from the myriad of ECM and truck/heavy vehicle manufacturers. Regardless of these frustrations, this source of information is not available from any other investigative technique and should not be overlooked as it can be critical to the reconstruction.

How to Use ECM Data to Best Effect

It’s important to remind readers that ECM data is not a substitute for any element of an investigator’s existing investigation protocol. It is a separate and distinct, additional element to be included in that protocol. Investigators can prepare for adding the retrieval of ECM data in their investigation methodology by reviewing the guidelines in ASTM E2493-07. Methods of data recovery can often come under scrutiny in court. Following forensic rules documented in the ASTM standard and the instructions provided in the software package is the best practice.

Downloading of data should occur as soon as possible after the event and prior to any inadvertent or malicious tampering with the vehicle’s electronics systems. Too often data is lost during the salvage process of the vehicle by carelessness. Knowing what information a specific ECM can provide is useful in guiding an investigator to the appropriate module so time is not wasted or data overlooked.

Engine Controllers

A truck’s ECM is often referred to as the engine’s “brain.” It is essentially a small computer attached to the side of the engine and receives data from different sources on the truck as well as reporting events or conditions. The engine controller of a truck can store data about a particular event such as a sudden deceleration or record a ‘snapshot’ of settings when an event has occurred.

However, as mentioned earlier, these controllers were not designed for accident reconstruction and as such might not have recorded the specific event the investigator is looking for. With experience, an investigator may be able to relate data captured about an event that occurred close to the time of the accident with the accident itself. It is recommended that an investigator examine all the surrounding evidence and treat data from the controller as an adjunct to the other evidence from the accident.

Modern engine controllers may contain information such as last brake or hard brake events or sudden decelerations, useful information for collision reconstruction. As new versions of engine controllers are developed, the information that they provide changes as well. Information provided by the engine controller of a 2002 vehicle may vary greatly to that provided by the controller for the same make of engine manufactured in 2012.

An example of how ECM data can be interpreted in an investigation is provided in the accompanying table of figures. The red arrows show a situation where the vehicle has stopped yet the engine load is high and neither the brake nor the clutch have been engaged. This indicates that the truck has likely struck something and stopped but the engine is still powering the transmission. The driver did not brake or engage the clutch prior to the impact. The brakes and clutch were eventually engaged and the vehicle moved forward slowly before coming to a final stop indicated by the dashed red line.

Brake Controllers

If we need to know if a driver swerved at the last minute to avoid something in the truck’s path, or gradually veered off the road due to the driver falling asleep, it will be data from the brake controller that will be most helpful. Commercial trucks have been equipped with electronic brake controllers since the late 1990s.

Events recorded by brake controllers include the number of hard and panic stops. If a driver is suspected of tailgating before a rear end collision, a long history of hard stops may indicate that the driver had a habit of following too close.

Many controllers in today’s braking systems are equipped with electronic stability and rollover prevention programs. These programs may use yaw sensors, horizon sensors, accelerometers, and steering angle sensors to prevent rollover and out-of-control conditions such as a tractor-trailer jackknife. Significant events are recorded and time-stamped in the controller’s memory and may prove to be valuable in collision reconstruction scenarios. A time-stamped yaw correction event just before an accident may help confirm that something suddenly ventured into the path of the truck, and the driver swerved in an attempt to avoid a collision. A series of severe rollover stability program (RSP) events in the hours before a rollover accident may support other evidence indicating an unstable load or a driver taking an exit ramp too fast.

Cab & Transmission Controllers

In addition to collision reconstructions, data found within cab and transmission controllers may be important during investigations of workplace accidents involving equipment such as integrated aerial trucks. Trucks and heavy vehicles that have been modified with third-party equipment often have the ECMs of that equipment integrated with the host vehicle’s data network. Logic programming features in modern cab controllers allow third-party equipment manufacturers to integrate functions and safety features with the vehicle. For example, a tree-trimming bucket truck controller may require a status report of the body stabilizers before allowing the hydraulic lift of the bucket to operate.

A Definitive Answer

In the grey areas that surround accident reconstructions, there is no definitive answer as to whether or not it is worth the time and money to retrieve critical event data from on-board electronic control modules. Are you willing to take the chance that a critical piece of the puzzle was ov erlooked for the sake of saving a little time or money?

The fact is that the technology for recording and retrieving this data continues to evolve, and there are real benefits for being an early adopter of this source of information not the least of which is a more thorough investigation and fact-based conclusion for your client.

Russ Colosi, VFI, CFEI, is a heavy vehicle forensic investigator with Arcon Forensic Engineers (www.arconeng.ca). Russ is a certified vehicle fire investigator with over 20 years experience.