Understanding the Types of Data Collected by Event Data Recorders (EDRs)

 

As forensic professionals, Garrett Forensics’ expert’s role is to extract, interpret, and present Event Data Recorder (EDR) information with precision. EDRs serve as objective digital witnesses to crash events, recording critical information moments before, during, and after a collision. Below is an expanded breakdown of key data categories—with real-world examples—to reinforce understanding and help analysts build strong, evidence-based reconstructions.

 

1. Pre-Crash Data
Pre-crash data typically spans the 5 seconds leading up to impact, recorded at half-second or one-second intervals depending on the vehicle manufacturer.

Examples:

Vehicle Speed:
A Chevrolet Silverado shows speeds of 45 mph, 47 mph, 50 mph, then 52 mph one second before impact—indicating acceleration before the collision.

Brake Application:
A Ford Explorer’s EDR shows “brake switch ON” 1.5 seconds before impact—consistent with sudden braking.

Throttle Position:
A Dodge Charger records a throttle percentage of 85% at T-2 seconds—suggesting aggressive acceleration.

Engine RPM:
A Honda Accord logs RPM climbing from 1800 to 3000 over the final 3 seconds—useful for correlating to throttle use.

Steering Input:
A Toyota Camry registers a -15° steering angle at T-0.5 seconds—indicating a sharp left swerve before impact.

 

2. Crash Pulse Data
Crash pulse data is crucial for estimating impact severity, energy absorption, and occupant injury potential.

Examples:

Delta-V (ΔV):
A 2018 Ford F-150 shows a longitudinal ΔV of 27 km/h over 100 milliseconds—suggesting a moderate front-end collision.

Acceleration/Deceleration Rates:
A 2019 BMW X3 indicates a peak deceleration of -21.5 g—consistent with a high-speed frontal collision into a rigid barrier.

 

3. Restraint System Status
Knowing the status and performance of restraint systems helps analysts assess occupant protection and injury mitigation.

Examples:

Seatbelt Usage:
A 2016 Nissan Altima reports “driver seatbelt latched = Yes” but “passenger seatbelt latched = No”—vital in determining injury severity.

Airbag Deployment:
A Jeep Grand Cherokee logs “front airbag deployed: driver at T+15ms; passenger at T+20ms”—aligning with front-end impact dynamics.

Pretensioner Activation:
A 2021 Hyundai Elantra shows “pretensioner fired = Yes” on both front seatbelts—indicating the system responded as designed.

 

4. System Status and Diagnostic Data
This data validates the reliability of recorded information and the operational readiness of safety systems.

Examples:

Ignition Cycle Counts:
An EDR shows the ignition cycle count at the crash as #1523, matching service records and helping establish the crash timeline.

Crash Data Retrieval (CDR) System Status:
A download log from a Bosch CDR tool reveals “Complete Event – No anomalies”—indicating an accurate and reliable data set.

Diagnostic Trouble Codes (DTCs):
A Chrysler Pacifica logs a prior DTC: B1B02 (passenger airbag fault)—which could impact airbag deployment analysis.

 

5. Post-Crash Data
Some EDRs capture data for a brief period after impact, providing context about what happened after the vehicle came to rest.

Examples:

Vehicle Rollover Data:
A 2020 Ford Explorer records “Rollover event: Yes, 1 quarter-turn”—evidence supporting a rollover claim.

Post-Collision Braking:
A 2022 Tesla Model 3 logs automatic emergency braking engagement at T+0.2 seconds—potentially limiting secondary impact damage.

Time Stamps:
A timestamp of “2024-10-18 14:52:16” precisely marks the event, aiding cross-referencing with surveillance or GPS data.

 

Manufacturer Variability and Retrieval Tools
Examples:

General Motors vehicles often log up to 5 seconds of pre-crash data, while some Toyota EDRs record 7 seconds.

Some newer Hyundai and Kia models provide lateral delta-V, rollover sensors, and multiple deployment thresholds.

Bosch CDR Tool, Tesla EDR Tool, and Hyundai EDR Retrieval Software must be matched with manufacturer-specific cables.

 

Conclusion
For Garrett Forensics certified EDR Analysts, understanding these nuanced data points—and recognizing their variability across manufacturers—is essential for producing accurate, court-admissible reconstructions. As vehicles grow more complex, so do their data systems. By staying grounded in the fundamentals and leveraging real-world case examples, analysts can translate raw EDR data into compelling forensic narratives.

Need help with interpreting a complex EDR case? Contact Garrett Forensics.