Commercial trucks are required under federal law to carry Electronic Logging Devices (ELDs) and many are also equipped with Event Data Recorders (EDRs) — often called "black boxes." This data can be the difference between winning and losing a serious truck accident case.
What the Black Box Records
A commercial truck's electronic data recorder captures a range of information in the seconds before, during, and after a crash:
- Vehicle speed at the time of impact
- Brake application — whether and when the driver braked
- Engine throttle position
- Steering inputs
- Seat belt usage
- Airbag deployment timing
- Hours of service data (via the ELD) — whether the driver was in compliance with federal rest requirements
In some newer trucks, dashcam footage is also stored and linked to the EDR system.
Why This Evidence Disappears
Here is the problem: most EDR systems overwrite their data on a rolling basis — often within 30 days, sometimes sooner if the vehicle is driven again after the accident. Trucking companies are not required to preserve this data automatically just because an accident occurred.
This is why the first days after a truck accident are critical. If a formal legal hold — called a litigation hold letter or spoliation letter — is not sent to the trucking company immediately demanding preservation of all electronic data, that evidence may be gone by the time you contact an attorney.
Trucking companies and their insurers know this. They often have their own teams on the scene within hours of a serious accident.
Federal Hours of Service Violations
Federal Motor Carrier Safety Administration (FMCSA) regulations limit how many consecutive hours a commercial truck driver can operate without rest. The ELD records this data. In many serious truck accident cases, the data reveals the driver was:
- Operating after exceeding the legal maximum driving hours
- Falsifying paper logs to hide violations
- Driving during mandatory rest periods
Hours of service violations establish negligence per se — meaning the violation itself is evidence of fault.
Other Evidence That Must Be Preserved Quickly
Beyond the black box, a comprehensive truck accident investigation should preserve:
- Driver qualification file — hiring records, license history, prior violations
- Maintenance and inspection records for the specific truck
- Trip and dispatch records
- Cell phone records — to check for distracted driving
- Cargo loading records — improper loading is a common cause of jackknife accidents
- Dashcam footage from the truck and nearby vehicles
What to Do Immediately After a Truck Accident
- Call 911 and get a police report
- Photograph everything at the scene — the truck, its plates, the DOT number on the cab
- Note the trucking company name displayed on the vehicle
- Get witness names and contact information
- Seek immediate medical attention
- Contact an attorney the same day — the preservation letter must go out immediately
Gonzalez Munoz Law has successfully handled serious truck accident cases throughout Miami-Dade and Broward County. We send litigation hold letters immediately and work with accident reconstruction experts to preserve and analyze black box data.
Call 305-770-6666 — 24 hours, 7 days a week. No fee unless we win.