The Automobile “Black Box”

This article will provide information regarding the black box which is extracted from an automobile (car, SUV or pick-up truck) after a crash.  Most cars will have what is commonly referred to as a “black box” also referenced as:

Event Data Recorder “EDR”

Crash Data Recorder

Airbag Control Module

What data does the black box record:

This device records certain data around the time of the accident.  It records the speed of the vehicle in 1 second increments, 4 seconds before the impact of the crash and will also record whether the brakes were on or off.  It must be noted, however, that the device does not measure precisely the point of impact.  The information recorded by the black box must be extrapolated typically by an expert, who will thereafter review the data and measurements and provide a report.

This evidence can thereafter be weighed with the evidence of the drivers of the subject vehicles, including police diagrams to determine accuracy including such facts of the point of impact.  These measurements can be very useful.

In Perez-Alarcon v. Lee, 2013 BCSC 408 (CanLII), the black box was retrieved and the measurements were able to determine the following:

 [28]        The “black box” data is consistent with Mr. Lee slowing to 66-68 kph 3 seconds before the collision, 64-66 kph 2 seconds before the collision, 62-64 kph 1 second before the collision, then Mr. Lee slamming on his brakes and hitting the pedestrian at a speed in the range of 52-54 kph. 

The engineer compared his calculations recovered from the data from the black box of the Defendant’s car and based on speed, and police measurements, it was determined that the Plaintiff pedestrian was “probably in the unmarked crosswalk at impact.”

In Gorman v. Meghji, 2018 BCSC 1904 (CanLii) the data extrapolated from the black box of the two vehicles in this horrific crash assisted the court with the analysis of fault, and based on the data retrieved, the emergency vehicle involved in this crash was held 80% at fault, while the civilian driver was only held 20% at fault.

“..both vehicles had Airbag Control Modules (“ACMs”) that were imaged and analyzed. These are the “black boxes” in a vehicle’s airbag system that record and preserve valuable information about the speed, acceleration and deceleration of a vehicle shortly before impact. I have considered that evidence along with the evidence of the expert witnesses called by the parties. After summarizing the evidence I set out my findings of fact and my conclusions on liability based on application of the relevant law.

To learn more about the Black Box see the following resources prepared by Kodsi Forensic Engineering:

Some key facts extracted from the video above:

  • Black box is also referred to as the “ACM” or airbag control module
  • Also referred to as the “EDR” or event data recorder
  • Typically found in cars, SUV’s and pick-up trucks
  • Automobile black boxes are very different from airplane black boxes
  • Automobile black boxes only record
  • Primary purpose of the black box senses forces and accelerations and decide whether or not to deploy airbags
  • Airbags are deployed within milliseconds when needed
  • Does not record every thing going on
  • Black box begins information usually 5 seconds before a crash
  • the ability to be able to give us a glimpse of just a few seconds before a crash is why this device was referred to as a “black box”

What Information does the black box record ?

Black box only records data when it senses higher-than-normal typical everyday forces and acceleration

Two Primary Events a black box Records

Deployment Event

When senses higher than normal accelerations and decides to deploy airbags, that is when it records a deployment event, including:

  • Speed
  • Brake application
  • Throttle use
  • A few seconds prior to the impact
  • Cannot be overwritten

Non-Deployment Event

When a vehicle experiences higher than normal accelerations but does not deploy airbags, but “wakes up” the black box this is a non-deployment event, which records some data:

  • Crucial: Data is volatile and can be overwritten
  • 2 events can cause non-deployment event to be overwritten
    • When another event is recorded and overwrites it
    • After a certain amount of key cycles
  • Non-deployment event data must be swiftly preserved after a crash

What kind of Information can be Found on a Black Box when an event has been recorded

  • Need consent from manufacturer of vehicle to extract data
  • Type of information that is recorded varies based on year, make and model

Data that may be available:

  • Speed
  • Speed change
  • Brake and throttle use
  • Seatbelt use

Newer Cars may also record:

  • Individual wheel speeds
  • Tire pressures
  • Odomotor readings
  • Gear position
  • VIN #
  • Steering input

Black boxes will include more information in future.

What information can the data assist with on your claim

  • Was the collision really a hit and run
  • Was there an occupant sitting in the front seat passenger seat
  • Were the occupants wearing their seat belt
  • What steering inputs were there before the collision
  • Were the brakes applied
  • Was the vehicle speeding

Data may not always be accurate and must be carefully reviewed by an expert.

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