Heavy Truck Event Data Recorders Expert Article

Many of the systems and components that record incident and crash data on heavy trucks are different than those found on conventional passenger vehicles. In this article, vehicle engineer Marcus Mazza, P.E. provides an overview of Heavy Truck Event Data Recorders (Black Boxes), including how they are different from automotive systems, what information is typically available, and other useful information for anyone investigating a heavy truck crash incident.

The experts at Robson Forensic investigate the full range of issues related to heavy truck incidents. We offer experts specializing in trucking operations, crash reconstruction, repair and inspection, vehicle and component design, and the download and analysis of HTEDR data. Please contact us for help determining which of our experts is best suited to address the technical issues in your case.

Heavy Truck Event Data Recorders

Automotive vs. Heavy Truck Event Data Recorders

There are a number of reasons why heavy truck event data recorder systems differ from their automotive counterparts; chief among them is that the majority of heavy trucks are not equipped with airbags. This difference is important because most passenger vehicles utilize the Airbag Control Module (ACM) to monitor vehicle accelerations, recognize crash events, and record relevant data. Absent airbags, and subsequently Airbag Control Modules, heavy trucks typically rely on information within the Engine Control Module (ECM) to identify recordable events. Rather than utilizing sophisticated accelerometers, event determination in heavy trucks is calculated by a more rudimentary algorithm that compares the change in vehicle speed over a particular period of time. These triggered events are sometimes referred to as hard brake or sudden deceleration events, and there is variation across the industry as to what thresholds are used to trigger a recordable event.

Event data for heavy trucks is not regulated in the same way as automotive systems. For instance, while the automotive industry has specific guidelines for data retention, required data fields, and data retrieval; within the heavy truck industry, vehicle manufacturers, engine suppliers, vehicle owners, and fleet operators have the option to adjust event trigger thresholds, data retention policies, or to disable event recorder systems altogether. Even accessing the data in heavy trucks can be significantly more complicated.

Heavy truck manufacturers utilize standardized diagnostic connectors, but each engine supplier requires unique software in order to access the data, and some manufacturers do not allow access to their data through publicly available hardware or software. The hardware and software requirements to access data from the Engine Control Module are determined by the make and model of the engine, rather than the manufacturer of the truck. Most heavy truck manufacturers do not produce their own engines and instead offer a range of engine options to suit the specific needs of their customers. For this reason, it will be important for your investigator to understand the specifications of the incident truck, beyond basic make and model.

In most instances, where vehicles have not been altered, necessary information can be derived from the Vehicle Identification Number (VIN). Compared to mass produced passenger vehicles, it is more complicated to access heavy truck EDR data and requires more specialized equipment. To prepare for unknown variables, Robson Forensic engineers arrive at heavy truck inspections equipped with a broad range of publicly available hardware adapters and software packages relevant to HTEDR extractions.

Heavy Truck Event Data Recorders - Available Data

The Engine Control Module was not originally designed with the intention of recording crash and hard brake event data. Designed to control the engine, the ECM monitors many of the same parameters found in a data download from an automotive Airbag Control Module, but the ECM lacks certain data sets that are specifically relevant to crash monitoring. Typical parameters monitored and stored by the ECM include:

  • Vehicle Speed – Measured in Miles Per Hour
  • Engine Speed – Measured in Revolutions Per Minute
  • Engine Load % - Actual Output Compared to Maximum Output
  • Throttle Position % - Percentage Throttle Pedal Application
  • Brake Status On/Off – Binary Expression of Brake Application
  • Clutch Status On/Off – Binary Expression of Clutch Application
  • Cruise Control Status On/Off - Binary Expression of Cruise Status
  • Malfunction Indication Light (MIL) or Diagnostic Code Status – Binary Expression of the Status

Figure 1: Hard Brake Event

Figure 2: Hard Brake Event Data

The lack of an accelerometer within the HVEDR prevents the system from capturing high fidelity vehicle acceleration and change in velocity (Delta-V) which are both commonly used by automotive crash investigators. This shortcoming in the HVEDR places additional onus on the reconstructionist to pinpoint the initiation of a crash within the triggered record. The large difference in mass between trucks and most road-going vehicles is so significant that in many instances the truck’s braking system imparts a similar or greater negative acceleration on the truck than the forces of the collision.

As a result, the event record will frequently be triggered by the application of the truck’s brakes in advance of any impact. Proper reconstruction of these events requires analysis of a multitude of other factors including vehicle damage, roadway markings, vehicle masses, etc. Nonetheless, the data recorded by the truck’s event recorder is a vital part in any reconstruction. Robson Forensic utilizes engineers to perform all vehicle crash investigations to ensure that proper interpretation of vehicle damage, crash scene evidence, and electronic data is applied to the facts in your case.

Preparing for a Heavy Truck Crash Investigation

Not all Engine Control Modules can be downloaded directly from the truck. In some instances where the truck has sustained substantial damage it may be necessary to connect the ECM to a surrogate truck or benchtop simulator with an engine/chassis simulator harness. In certain instances the best option is to send the unit out for analysis There are some instances where data from the ECM is lost. This can occur from severe damage to the ECM, in some configurations where electrical power is removed from the system, and in other instances where incident data is overwritten by subsequent triggered events.

If working with Robson Forensic on your heavy truck crash investigation, the expert performing your inspection will be knowledgeable in the best methods to preserve and extract the data relevant to your case. In most instances the engineer who downloads the ECM will be qualified to inspect braking and suspension systems, perform a detailed inspection of the crash scene, and conduct an accurate and reliable reconstruction. In preparing for your investigation, your forensic expert will want to know the following information:

  • Make and Model of Truck
  • Model Year
  • Vehicle Identification Number
  • Engine Manufacturer and Model
  • Location of Crash
  • Current Location of Cab/Trailer

Alternate Data Sources

Other data sources exist that may warrant consideration and discussion with your technical expert. Robson Forensic maintains in-house expertise in the extraction and analysis of data from cell phones, GPS units, vehicle infotainment systems, and other trucking industry specific fleet management systems.

Heavy Truck Crash Investigations

The trucking expertise at Robson Forensic covers every aspect of the industry; we employ a variety of engineers and scientists who specialize in fields relevant to vehicle and roadway engineering, human performance, commercial trucking operations, injury analysis, and toxicology. Submit an inquiry or contact the author of this article for more information.

Featured Expert

Marcus A. Mazza, Automotive Engineer & Crash Expert

Marcus A. Mazza, P.E.

Automotive Engineer & Crash Expert
Marcus Mazza is an automotive engineer with diverse experience in production vehicles, military vehicles, and motorsports. He applies his expertise to intellectual property disputes as well as vehicle… read more.


View All Articles

Automotive Repair Standard of Care

By Marcus A. Mazza
Expert Overview

In this article, automotive engineer Marcus Mazza shares his expert insight on the standard of care for vehicle maintenance and repair stations. What Is the Standard of Care for Vehicle Maintenance…

Heavy Truck Crash Reconstruction

By Robson Forensic
Expert Overview

This article provides an introduction to heavy truck crash reconstruction, including an explanation of why the Conservation of Energy (COE) method is crucial for accurate and reliable reconstructions.…

Unintended Vehicle Acceleration

By Marcus A. Mazza
Expert Article

Through the course of our casework we have seen numerous cases involving claims of unintended vehicle acceleration. Whether our investigation determined that the cause was electrical, mechanical, or…