The Role of Truck “Black Box” Data in South Carolina Trucking Accident Cases

When a serious trucking crash happens on South Carolina roads—from I95 and I26 to rural two lanes—the most powerful evidence may be inside the tractor itself: the engine control module (ECM) or event data recorder (EDR). Used properly, this data can corroborate physical evidence, clarify timelines, and rebut inaccurate narratives.

Below is a practical guide tailored to South Carolina law and procedure.

What "Black Box" Data Really Is on a Tractor-Trailer

Passenger vehicles often store crash data in a dedicated EDR integrated with the airbag control module. Heavy commercial vehicles are different. Most tractors store operational snapshots in the ECM (sometimes called a heavy-vehicle EDR or HVEDR). Many fleets also run Electronic Logging Devices (ELDs) and separate telematics platforms. These systems are distinct:

ECM / HVEDR (engine module): Typically records speed, engine RPM, throttle %, brake switch, clutch switch, cruise control status, and similar parameters around certain triggered events (e.g., a “hard brake” event or a “last stop” record). The duration and resolution of data vary by engine manufacturer and model.- ELD (hours-of-service compliance): Records driver duty status and timekeeping to satisfy federal hours-of-service rules. It is not the same as the ECM snapshot.- Telematics / fleet systems: May store GPS breadcrumbs, harsh-event flags, camera footage, ADAS alerts, and maintenance codes. Retention is contract and vendor-specific.

Key takeaway: Do not assume tractor data looks like passenger-car crash data. Identify and pursue all three sources—ECM, ELD, and telematics/cameras.

Typical Heavy-Truck Data You Can Expect

HVEDRs typically record vehicle speed, brake usage, and diagnostic trouble codes. More specifically:

Vehicle speed (1 Hz sampling common around a triggered event)- Brake switch status and timing- Throttle % / engine load- Clutch switch status- Cruise control on/off- “Hard brake” and “last stop” snapshots (often tens of seconds to a couple of minutes of pre-event data, plus a brief post-event window)- Fault codes and certain maintenance alerts- From ELD/telematics (separate systems): driver duty status changes, GPS location history, harsh events, and sometimes camera video or ADAS alerts

Caution: Many tractors have no airbags, and ECM snapshots generally do not contain delta-V or seatbelt-use fields typical of passenger-car EDRs.

How This Data Proves Negligence and Causation

Contradict driver narratives. Speed, throttle, and brake-switch timing can rebut claims of “I was going 55” or “I braked immediately.”- Establish timeline and perception-reaction. Hard-brake/last-stop records help fix when the driver perceived the hazard and how they responded.- Show regulatory and policy breaches. Telematics/ELD logs can indicate speeding patterns, harsh-event frequency, and hours-of-service problems. Maintenance/ABS faults can corroborate equipment issues.- Strengthen reconstruction. Combining ECM snapshots with scene evidence (skid marks, crush, yaw, camera footage) anchors a defensible reconstruction.

South Carolina's Modified Comparative Negligence (51% Bar)

In South Carolina, an injured person can recover as long as their fault does not exceed 50%. Objective truck data often reduces disputed fault percentages by showing excess speed, delayed braking, or non-compliance—directly impacting apportionment and damages.

Example: If a jury finds the plaintiff 20% at fault and the truck driver 80% at fault on $500,000 damages, the net recovery is $400,000. Without objective data, the defense may succeed in pushing the plaintiff’s share above 50%, eliminating recovery entirely. Preserve the Data Immediately (and Broadly) Act fast. Some ECM records are overwritten by later operation; telematics vendors may purge data under short retention policies.

Send a comprehensive preservation letter (litigation hold) to the motor carrier and its insurer, identifying:

Tractor and trailer ECM/HVEDR images and configuration files- ELD raw data and exported reports- Telematics data (GPS breadcrumbs, harsh-event logs), dashcam and ADAS video/alerts- Qualcomm/OmniTRACS/PeopleNet/Samsara/Geotab or other platform data- Driver qualification file, training, dispatch communications, bills of lading, maintenance/inspection records, and the FMCSA accident register entry

Follow with Rule 45 subpoenas and, once filed, Rule 34 requests specifying native formats/metadata. Where appropriate, seek early protective orders/TROs to secure the truck and modules for inspection and imaging.

Admissibility and Foundations (South Carolina)

Authentication & chain of custody: Document who extracted what, when, how, and with which tools; preserve hashes and read-only images.- Expert testimony: Use qualified ECM/EDR and reconstruction experts; pair snapshot fields with physical evidence.- Method reliability: Explain manufacturer-specific triggers and sampling so the court understands the limits and strengths of the data.

South Carolina Limitations Periods (overview)

General personal injury: 3 years from discovery.- Government defendants (Tort Claims Act): Generally 2 years (extendable to 3 years if a verified claim is timely filed). Don’t let the shorter TCA window jeopardize preservation or suit timing.

Wrongful death, medical malpractice, and other categories have additional rules—evaluate case-specific deadlines immediately.

Insurance Context

South Carolina minimum auto limits: $25,000/$50,000 bodily injury and $25,000 property damage (25/50/25). Commercial motor carriers in interstate commerce typically carry much higher liability limits (often $750,000+; more for certain cargo/hazmat), so proving liability with hard data can materially affect settlement value.

Practical Timeline (South CarolinaFocused)

Window Practical Risk Recommended Action 0–7 days Truck towed/repaired; ECM snapshots overwritten by subsequent operation; short vendor retention for camera/telematics

Issue preservation letters and insurer notice immediately; request the truck be taken out of service until modules are imaged; ask the carrier to suspend autodeletion. 8–30 days Some fleets auto-purge certain telematics/camera clips; ELD malfunction remediation deadlines can be misread Follow up on the hold; request native exports from ELD/telematics; if resistance, file early suit and move for a preservation order.

≤ 6 months Hours of service supporting documents must be retained by carriers for at least 6 months; delays risk loss of complementary HOS evidence Serve Rule 34 requests specifying native formats/metadata; seek Rule 30(b)(6) on data systems and retention.

Up to 3 years FMCSA accident register and required accident reports must be kept 3 years, but do not include ECM/EDR content

Request the register and all required accident reports; do not rely on this to capture ECM/EDR/telematics.

Working With the Right Experts

Heavy-truck data is manufacturer-specific. Retain experts who:

Carry the correct cables/software and can image without altering source data- Can explain triggers (e.g., “hard brake” vs. “last stop”) and sampling intervals- Will marry the data to scene evidence, vehicle inspections, and any camera/ADAS feeds

South Carolina-Specific Strategy Checklist ☐ Send a detailed preservation letter within days ☐ Seek consensual imaging or move quickly for a court order ☐ Demand native ECM/ELD/telematics exports and configuration files ☐ Notice a 30(b)(6) deposition on data systems and retention ☐ Establish airtight chain of custody and expert foundations ☐ Calendar the 3-year general PI SOL and any 2 or 3-year TCA deadlines

Bottom Line

Objective truck data—properly preserved, extracted, and explained—can be outcome-determinative under South Carolina’s modified comparative negligence framework. Move fast, be specific about the sources you want, and build a record that survives admissibility challenges and persuades adjusters and juries alike.

For help preserving and using ECM/EDR, ELD, and telematics evidence in a South Carolina trucking case, contact Proffitt & Cox. [](https://www.proffittcox.com/when-snow-falls-in-columbia/) News and Articles When Snow Falls in Columbia What Property Owners and Visitors Need to Know About Slip-and-Fall Liability If you’ve lived in Columbia or anywhere in South Carolina for long, you know

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September 30, 2025 [](https://www.proffittcox.com/the-role-of-truck-black-box-data-in-south-carolina-trucking-accident-cases/) News and Articles The Role of Truck “Black Box” Data in South Carolina Trucking Accident Cases When a serious trucking crash happens on South Carolina roads—from I95 and I26 to rural two lanes—the most powerful evidence may be inside the tractor

August 27, 2025

Proffitt & Cox, LLP

The Role of Truck “Black Box” Data in South Carolina Trucking Accident Cases