Black Box Data: How Truck Computers Prove Fault in Crashes
Commercial trucks carry electronic evidence that can prove the driver was speeding, fatigued, or braking late. Texas truck accident lawyer Byron Bailey explains how we use it.
Most people know that airplanes have black boxes. What they don't know is that 18-wheelers and commercial trucks have them too — and the data stored inside can be the most powerful evidence in a truck accident case.
What Is a Truck's Black Box?
Commercial trucks are equipped with an Engine Control Module (ECM) — sometimes called an Event Data Recorder (EDR). This device continuously records critical operational data. Most also now carry Electronic Logging Devices (ELDs), mandated by the FMCSA since 2019, which record hours of service electronically.
What Data Does It Capture?
The ECM/EDR records data including:
- Vehicle speed before, during, and after the crash
- Brake application timing and force
- Engine RPM and throttle position
- Seat belt status
- Steering inputs
- Hard braking events and sudden decelerations
The ELD records hours of service compliance — proving whether the driver had exceeded federal hours-of-service limits and was fatigued at the time of the crash.
Why This Evidence Disappears Fast
ECM data is typically stored on a rolling loop. Older data is overwritten as new data comes in — sometimes within 30 days, sometimes less. Trucking companies have no legal obligation to preserve this data unless they receive a litigation hold notice from an attorney.
This is why we issue litigation hold letters immediately after we're retained — often within 24 to 48 hours of your call. Waiting costs you this critical evidence.
How We Use It at Trial
Our accident reconstruction experts extract and interpret the ECM and ELD data. If the data shows the driver was traveling at 72 mph in a 55 mph zone with no brake application before impact — that's not just evidence of negligence. It's evidence of recklessness that can support a claim for punitive damages.
Dash Camera Footage
Many modern commercial trucks also carry forward-facing and cab-facing dash cameras. This footage can show driver distraction, running red lights, lane changes, and the seconds leading up to impact. We demand this footage immediately.
Frequently Asked Questions
Q: Can a trucking company destroy black box data legally?
A: Once they receive a litigation hold letter from your attorney, destroying evidence constitutes spoliation — which can result in sanctions and adverse jury instructions. That's why calling an attorney immediately is critical.
Q: Are all trucks required to have ELDs?
A: Most commercial carriers are required under FMCSA 49 C.F.R. Part 395. Some short-haul and older vehicle exemptions exist.
Injured in Texas? Call Byron C. Bailey & Associates FREE: 214-223-6400 | byronbaileylaw.com. No fee unless we win.