Event Data Recorder (EDR)

What is an Event Data Recorder and How Does it Operate?

A vehicle’s Event Data Recorder (EDR), often referred to as the “Black Box” is a device inside a vehicle that records data regarding vehicle dynamics, vehicle operation and safety system information in the moments surrounding a crash.  The technology to “download” the data from an EDR has been commercially available since 2000.  Since 2013, most vehicles sold in the United States record EDR data that can be retrieved following a crash.

The EDR is typically a part of a vehicle’s Airbag Control Module (ACM).  The ACM is an onboard computer which is constantly monitoring the output of safety sensors around the vehicle.  When the ACM detects a signal that is consistent with a crash, it “wakes up” and performs computations to determine if it needs to deploy supplemental restraints, such as airbags or seat belt pre-tensioners.

If the ACM determines that a deployment is necessary, the EDR records what is called a Deployment Event.  This information is permanently written to the EDR and cannot be overwritten.  Deployment Events are associated with moderate to severe crashes and, as a result, are often associated with severe vehicle damage.  In these circumstances power may be lost to the ACM and the EDR data must be imaged directly from the ACM, which must be extracted from the crashed vehicle.  In very serious crashes, the EDR may lose power before all the information can be recorded.

If the ACM “wakes up” but does not determine that a deployment is warranted, the EDR records what is called a Non-Deployment Event.  Non- Deployment Events result from rapid speed changes experienced by the vehicle.  These speed changes can be the result of minor to moderate impacts, and, depending on the sensitivity of the ACM, can be the result of more minor driving events, such as curb impacts.

Non-Deployment Events are recorded by the EDR.  Subsequent Non-Deployment Events will also be recorded by the EDR, but a subsequent Non-Deployment Event may overwrite a prior Non-Deployment Event. It is common for an EDR to have memory available to record three separate events, and, therefore, a Non-Deployment Event will be overwritten every third Non-Deployment Event.  Therefore, it is a good idea to download the data as close as possible to the crash date.  If an EDR has multiple events recorded, a skilled technician can use the Ignition Cycle (the number of times the ignition has been turned on) that was recorded at the time of the event to help determine which event pertains to the crash of interest.

CDR900_2 EDR


Vehicles have been recording crash data since the early 1990’s.

As of 2012, the federal government has regulated the information that must be reported by…..

What is Recorded?

There are certain parameters set forth in the Code of Federal Regulations, Title 49, Part 563 (49 CFR part 563), which must be recorded by the EDR.  However, auto manufacturers may record whatever they choose, as long as these minimum standards are met.  49 CFR part 563 mandates certain recording times, recording intervals and data sampling rates.  EDRs are required to record data for frontal, side and rear impact collisions.  Some of the data elements required by 49 CFR part 563 are:

  1. Longitudinal Speed Change
  2. Lateral Speed Change
  3. Vehicle Roll Angle
  4. Safety Belt Usage
  5. Steering Inputs
  6. Brake Usage
  7. Accelerator Usage
  8. Pre-impact Speed (5 seconds prior)

Along with the data listed above, the EDR will record information such as Anti-lock Brake System activation, ignition cycle, airbag deployment and any other information the manufacturer chooses to record.

The EDR also records data regarding the crash severity.  The EDR will record longitudinal and lateral Delta-V.  Delta V is the speed change experienced by the vehicle during the crash.  This is the major descriptor of crash severity used in automotive injury research.  In addition to the Delta-V, the EDR will record the crash pulse, or the time history of the acceleration of the vehicle during the crash.

Who can access the data?

The driver privacy act of 2015 declares that any data in an EDR  is the property of the owner or lessee of the vehicle in which the recorder is installed, regardless of when the vehicle was manufactured.  This act Prohibits a person, other than the owner or lessee of the motor vehicle, from accessing data recorded or transmitted by such a recorder unless:

  • A court or other judicial or administrative authority authorizes the retrieval of such data subject to admissibility of evidence standards;
  • An owner or lessee consents to such retrieval for any purpose, including vehicle diagnosis, service, or repair;
  • The data is retrieved pursuant to certain authorized investigations or inspections of the National Transportation Safety Board or DOT;
  • The data is retrieved to determine the appropriate emergency medical response to a motor vehicle crash; or
  • The data is retrieved for traffic safety research, and the owner’s or lessee’s personally identifiable information and the vehicle identification number are not disclosed.

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