April 22, 2021Data Downloads

A crucial piece in the crash reconstruction puzzle.

For crash investigators and reconstruction technicians, information is key in determining how a collision occurred. At Kittelson LLC, we view each reconstruction case as a puzzle. Having only one piece does not allow you to fully understand what happened – you need multiple pieces to complete it. One crucial piece of the reconstruction puzzle is a data download from all vehicles involved. A download from a vehicle can fill in missing information if roadway evidence is not present during a site investigation. It can also verify and emphasize reconstruction calculations.

What is a Download?

A passenger vehicle download is the retrieval or imaging of crash related data stored within the vehicle. Download data from a passenger vehicle has become a pivotal component in crash investigations and reconstruction. Considering collision situations where roadway evidence is not available or disappears quickly, a vehicle download may be the missing piece needed to explain what happened and how a collision occurred.

Airbag Control Module

Typically, data is stored in the airbag control module (ACM) which is commonly referred to as a “black box”. The ACM can be found in various places but typically near the vehicle’s center of gravity, such as under the driver’s seat, center console or behind the dashboard. Information stored by the ACM includes telemetry data such as vehicle speed, engine revolutions per minute (RPM), throttle position, brake status, cruise control status, steering inputs, seat belt status, and ignition cycles.

Electronic Data Recorders

The majority of passenger and commercial vehicles operating on our busy roads also have electronic data recorders (EDRs) contained within the ACM. An EDR can record and store data parameters related to a collision sequence. Data recorded and stored may vary on what EDR generation or manufacturer requirements are present, though the National Highway Traffic Safety Administration (NHTSA) specifies requirements for consistency in the collection, storage, and retrievability of crash data.

The parameters available provide data to answer common questions about the crash. Most vehicles record pre-crash data: either two and a half or five seconds, Delta V (the change in speed over time), and longitudinal and lateral acceleration data (front/rear and side to side movements).

A common misconception is that a vehicle is recording everything the operator does. An EDR only records certain data parameters when event criteria are met. The most common in passenger vehicles are airbag deployment and non-deployment events. Deployment level is just that: an airbag or other safety device deployed. A non-deployment level is a situation where collision forces are sensed but may not warrant the need for safety device deployment. That means even if the airbags did not deploy, data may be present in the EDR.

For commercial vehicles, data is recorded by also meeting event thresholds. However, instead of airbag deployments, a commercial vehicle uses set acceleration/deceleration or last stop threshold. They tend to record longer periods of time of the data parameters.

With either of these types of vehicles, we cannot know unless we check first!

How is this Information Obtained?

Kittelson LLC and our team of certified crash reconstruction technicians use highly specialized hardware and software to obtain this data. By connecting through a car’s diagnostic port (OBDII) or directly to the vehicle’s airbag module, the crash data can be imaged. The Bosch Crash Data Retrieval (CDR) interface is the standardized equipment used among investigators allowing for efficient and accurate data collection.

To find out more about downloads or ask if a vehicle you have is supported and what data may be present, give us a call.