Commercial Vehicle Accident Reconstruction

Heavy Truck, Semi Tractor-Trailer, and Articulated Vehicle Crash Analysis

Accidents involving commercial vehicles are often associated with large financial loss and significant injuries to the occupants of other vehicles involved. A fully loaded tractor-trailer can weigh 80,000 pounds, which is nearly twenty times as much as a passenger vehicle. This large difference in weight can complicate the accident reconstruction with seemingly disproportionate damage. Additionally, the difference in weight between a fully loaded semi tractor-trailer versus a passenger vehicle can mean that the injury severity and impact severity are much more amplified for the lighter vehicle.

Commercial vehicles are heavy-duty trucks by many different names:

Semi Tractor Trailers
Heavy Trucks
Multi-Axle Trucks
Concrete Trucks (In-Transit Mixers)
Box Trucks
Garbage Trucks
Over The Road (OTR) Trucks
Long-Haul Trucks

Some areas of investigation that are unique to commercial vehicles include:

Brake Systems Analysis
Analysis of "Black Box" Data from the vehicle's Engine Control Module (ECM)
Analysis of Onboard Camera Footage (a.k.a. DashCam, or DriveCam),
Global Positioning System (GPS) Data

Our forensic engineers understand the mechanical systems of commercial vehicles and are experienced at incorporating their unique data and evidence into our commercial vehicle accident reconstructions. Please review the sections below for more information on unique areas of investigation tailored to commercial vehicle accident reconstruction.

Commercial Vehicle Braking Systems

The braking systems utilized on commercial vehicles are substantially different than the systems used on passenger vehicles. Commercial vehicles frequently utilize air brake systems while passenger vehicles employ hydraulically actuated systems. Air brake systems, (a.k.a. pneumatic brake systems) are relatively simple in their construction and have proven to be robust and reliable systems when properly maintained. However, air brake systems are not infallible and require frequent inspection to ensure their proper operation. Brake systems that are air actuated are manufactured under specifications that rely on frequent inspection following rules set forth by federal standards.

The standards related to brake system inspection are described in the Code of Federal Regulations (CFR) 49, part 396. This standard, frequently referred to as the DOT inspection standard, outlines that brake systems must be inspected for proper operation and condition. Common adjustment terms that are used in the field include “slack adjuster” and “pushrod stroke”, as well as “lining thickness”, to name a few. Typically a DOT inspection is performed routinely on a commercial vehicle, however there are many times where a semi with bad brakes has been involved in an accident, requiring a specialized eye to determine if the brakes contributed to the said accident. Veritech Engineers have performed hundreds of commercial vehicle accident reconstructions and are often called upon to evaluate the condition and operation of a vehicle’s air brake system to determine if it contributed to the accident.

Commercial Vehicle Black Box and Engine Control Module Data

“Black box” data associated with commercial vehicles involved in an accident is becoming more common and is proving to be a valuable tool for accident reconstructionists. There are several sources for obtaining pre-crash data from a commercial vehicle; the most common source of data comes from the vehicle’s Engine Control Module (ECM). Beginning in the late 90’s, manufacturers starting incorporating the ability to access the ECM for data analysis after an incident; currently every major commercial vehicle manufacturer supports ECM data downloads for newly manufactured vehicles. It is important to note that, although the ECM may contain valuable pre-crash information, the ECM recording capability was developed primarily to aid service and maintenance personnel and was not originally intended to be used as an accident reconstruction tool.

In addition to the semi tractor-trailer Engine Control Module, there are other modules that have valuable data stored on them. For instance, a truck’s brake controller typically stores faults and errors associated with the truck’s braking system. Because most heavy trucks are an assembly of different components from different manufacturers, it is common to have components that are designed to log data individually, and communicate directly with the vehicle’s ECM. Therefore, these individual components, such as brake controllers, may have an impressive data logging capability. Knowing how to properly interpret this data, and correlate such data to an accident or physical evidence, is the job of a competent forensic engineer.

Veritech engineers understand the capabilities, limitations and pitfalls of the various manufacturers’ systems and are skilled at accurately interpreting the recorded data. There are certain nuances that must be known prior to attempting a data download from a multi-axle semi, and in extreme cases, if these nuances are not known and accounted for, the stored data can be deleted or overwritten. Therefore, knowing how to safely access the data before the download is performed is imperative. The data recorded by each manufacturer’s ECM does not follow a standard protocol, which, in addition to complicating the download, also results in potential pitfalls and misinterpretation by inexperienced accident reconstructionists. Veritech's forensic engineers have experience in accident reconstruction involving commercial vehicles and have authored peer-reviewed publications with the Society of Automotive Engineering on aspects related to commercial vehicle accident reconstruction.

Commercial Vehicle Dashboard Camera Video Analysis

More and more, it is becoming common for all types of cars, trucks, and semis to utilize an onboard camera that constantly records a video of the events occurring during an operator’s drive. The view is typically out the front of the vehicle and through the windshield, pointed in the direction that the driver is viewing. These cameras are often wide-angle views, meant to capture a wide range of view during recording, and can typically record a snippet of video at the command of the vehicle’s driver.

On-board cameras that are custom tailored to semi tractor-trailers and other commercial vehicles are manufactured by many companies, however two of the biggest names in the industry are DriveCam and DashCam. Videos that record a subject accident provide useful information pertaining to the accident. Moreover, Veritech’s photogrammetry and videogrammetry capabilities allow us to take these videos even further, and extract scientifically accurate measurements, distances, speeds, and even accelerations from the vehicles through the video. This advanced analysis of videos has proven to be extremely useful in accident reconstruction, determining perception-reaction issues, and determining accurate time and space relationships for the moments leading up to and accident. Forensic engineers at Veritech pride themselves with being industry leaders in the areas of photogrammetry and videogrammetry and have successfully implemented these cutting-edge techniques for hundreds of accident reconstructions .

Commercial Vehicle GPS Data Analysis

Another piece of technology used routinely on semi-tractor trailers and other commercial vehicles is tracking provided by Global Positioning System, otherwise termed GPS data. The data from GPS tracking typically includes vehicle position at one-second intervals. From this incremental GPS positioning, items such as speed and acceleration calculations can be determined. It is important to note that GPS data is not perfect. The biggest issues are two-fold: First, the refresh rate of the data is typically provided every second. In accident reconstruction, a lot can happen between the one second intervals, and these events may not be recorded by the GPS system.

Secondly, GPS position can be relatively inaccurate compared to true location. For example, typical positioning error can be on the order of 7 to 10 feet. In forensic engineering and accident reconstruction, an error of possibly 10 feet could have a noticeable influence on the speed and position calculations. These issues, while not insurmountable, need to be considered by a forensic engineer with experience in dealing with GPS data.

Dynamics Associated with Articulated Vehicles

Inherent with many commercial vehicles is the ability to haul loads carried on trailers. These trailers can haul a significant amount of weight. Moreover, semis have the ability to tow more than one trailer at a time. The articulation of tractor trailers as they navigate roadways results in unique dynamics or behaviors that must be taken into consideration during a commercial vehicle accident reconstruction. Trailers pivot around a single point, referred to as a kingpin, which can become detached during an accident. This scenario leads to a vehicle that was influenced by the trailer connection prior to the collision, but not influenced after contact. Therefore, special care must be used in reconstructing these accidents. Determining vehicle dynamics with articulated vehicles takes into consideration “off-tracking” of the wheel paths , trailer dynamic stability, as well as the weight distribution and vehicle geometry.

Veritech's engineers have experience in accident reconstruction involving commercial vehicles and have authored peer-reviewed publications with the Society of Automotive Engineering on aspects related to commercial vehicle accident reconstruction.

Please contact one of our licensed professional engineers at 303-660-4395 to discuss your commercial vehicle accident reconstruction case and receive a free initial consultation with honest and candid comments.

Mark Kittel, P.E., D.F.E.

Principal Engineer

Joe Tremblay, P.E., D.F.E.

Principal Engineer