What is EDR?

An EDR (Event Data Recorder) is a device or function - often built into a vehicle’s airbag control module or other onboard system - that records technical data from the moments before, during, and after an event (crash).

Key Facts About EDRs

Primary Purpose: Improve vehicle safety and help crash investigators understand what happened during an accident.
Data Recorded:

Vehicle speed
Brake application
Accelerator position
Seat belt usage
Airbag deployment timing
Steering inputs
Engine RPM
Change in speed (delta-V) during impact

An Event Data Recorder (EDR) will store data when a crash-like condition meets certain trigger thresholds programmed into the vehicle’s control modules — most often the airbag control module (ACM).

These triggers fall into two main categories:

1. Deployment Events

(Airbags and/or seatbelt pretensioners deploy)

Primary trigger:
The crash pulse (change in velocity, or ΔV) exceeds a programmed threshold in a particular direction (frontal, side, rear).
Examples of deployment triggers:
- Frontal impact exceeding a set g-force/ΔV threshold
- Side impact exceeding the side-sensor threshold
- Rollover detected by gyroscopic sensors triggering curtain airbags
- Multiple impacts where combined forces exceed limits

What gets recorded:

Full suite of pre-crash (often up to 5 seconds) and crash-phase data
Post-crash data (a few hundred milliseconds to seconds after deployment)
Complete crash pulse waveform

2. Non-Deployment Events

(Airbags don’t deploy, but a moderate impact or change in velocity occurs)

Primary trigger:
A crash-like deceleration is detected, but it’s below the deployment threshold.
Why record these?
They can still be useful for injury analysis and to corroborate evidence.
Examples:
- Low-speed collision with noticeable deceleration
- Hitting a large pothole or curb hard enough to trip the sensing algorithm
- Sudden hard braking with rapid deceleration, but no impact requiring airbags

What gets recorded:

Often fewer data fields than deployment events
Still may include pre-crash speed, brake use, and throttle position
Shorter crash pulse data or “snapshot”

Key Points About Triggers

Thresholds vary by manufacturer & model year
A 2024 SUV may have different ΔV and g-force settings than a 2010 sedan.
Not every hard bump stores data — the algorithm distinguishes between “rough road” signals and true crash events.
Multiple events
If a second crash happens quickly after the first (e.g., hitting another car, then a guardrail), the EDR can sometimes record both in the same file.

EDR retrieval tools are a reliable, versatile, and increasingly powerful industry standard platform that retrieves EDR crash data from the vast majority of modern vehicles.