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This article is for general informational purposes only and does not constitute legal advice. It does not create an attorney-client relationship. Every trucking accident case involves unique facts and applicable law. Consult a licensed Louisiana attorney about your specific situation. *Attorney Advertising.*
When an 18-wheeler is involved in a serious crash, the truck itself is a witness. Commercial trucks carry electronic systems that record what the vehicle and driver were doing before and after a collision.
Getting that data quickly, before it is destroyed or overwritten, is often the most critical step in building an injury or wrongful death claim in Louisiana.
Most people who hear “black box” assume there is a single device recording everything. Commercial trucks are more complicated. There are two distinct electronic systems, and they capture very different categories of data.
| Feature | ELD (Electronic Logging Device) | ECM / HVEDR (Electronic Control Module / Heavy Vehicle Event Data Recorder) |
| Primary purpose | Hours of Service (HOS) compliance | Engine management (fuel injection, throttle, emissions) |
| Common nickname | Electronic log | “Black box” |
| Connected to | Truck engine (for automatic drive-time recording) | Engine computer; HVEDR function in ECM or ABS module |
| What it captures | Driver duty status, location, engine hours, miles driven | Speed, braking force, throttle position, engine RPM |
| Recording trigger | Continuous / automatic when vehicle moves | Event-triggered (extreme deceleration, collision) |
| Crash reconstruction use | Limited — not designed for it | Yes — captures vehicle behavior in seconds before impact |
| Data manipulation rules | Prohibited under 49 C.F.R. § 395.30 | Separate rules governing retention and spoliation |
| Speed before crash | Not recorded | Recorded |
The ELD (Electronic Logging Device) is a regulatory compliance tool. Federal law requires most interstate commercial truck drivers to use an ELD to record their hours of service: how long they have been driving, when they rested, and whether they complied with federal limits on consecutive driving hours.
An ELD is connected to the truck’s engine and automatically records driving time, but its primary purpose is Hours of Service (HOS) compliance, not crash reconstruction.
The ECM (Electronic Control Module) is the truck’s central engine computer. While often generically called the “black box,” the ECM’s primary job is actually running the engine (fuel injection, throttle, emissions). However, most modern heavy trucks feature an integrated Heavy Vehicle Event Data Recorder (HVEDR) function within the ECM or ABS module. When the system detects a trigger—such as an extreme deceleration event or a collision—the HVEDR captures a snapshot of vehicle performance data: speed, braking force, throttle position, and engine RPM. This data speaks directly to what the vehicle was doing in the critical seconds before impact.
Understanding the difference matters because the rules governing each system, including what must be kept, for how long, and under what circumstances a court can sanction a carrier for losing it, are not the same.
| Data Element | Notes |
| Date and time | Automatically logged |
| Vehicle location | Latitude/longitude, converted to nearest identifiable location |
| Engine power status | On / Off |
| Vehicle motion status | Moving / Stopped |
| Miles driven | — |
| Engine hours | — |
| Driver duty status | Off duty, sleeper berth, driving, or on duty/not driving |
| Log edits and annotations | Original unedited data retained alongside any changes |
| NOT recorded | Speed, hard braking, steering, throttle position, RPM |
Under 49 C.F.R. Part 395, Subpart B, Appendix A, a compliant ELD automatically records and retains the following data elements:
Because the ELD is synchronized with the engine, driving time is recorded automatically, and the driver cannot manipulate it by forgetting to log in. The ELD also records any edits or annotations made to the log, along with the original unedited data. A carrier is prohibited from altering or erasing original ELD data under 49 C.F.R. § 395.30.
What an ELD does not record: ELDs are not required by federal regulation to capture vehicle speed, hard braking events, steering behavior, throttle position, or RPM. Those are ECM functions, not ELD functions. A driver who was operating at 85 miles per hour just before a crash will not have that data in the ELD; it will be in the ECM.
| Data Element | Notes |
| Vehicle speed | Captured at the moment of a trigger event |
| Braking force | Indicates whether and how hard the driver braked |
| Throttle position | Shows driver input on the accelerator |
| Engine RPM | Reflects engine load and vehicle behavior |
| Primary engine functions | Fuel injection, throttle control, emissions management (core ECM job — not crash data) |
| Recording trigger | Extreme deceleration event or collision — not continuous |
| Where HVEDR lives | Integrated within the ECM or ABS module |
| What the data shows | Vehicle performance in the critical seconds before impact |
| NOT recorded | Driver hours, duty status, location logs, log edits (those are ELD functions) |
The ECM is the truck’s engine control computer. However, it will also “record” the information it is processing during a wreck to a backup system called a Heavy Vehicle Event Data Recorder (HVEDR).
Depending on the make, model, and year of the truck, it typically captures:
In a serious collision, forensic download of the ECM can establish whether the truck was traveling above the posted speed limit, whether the driver applied the brakes (and when), and whether the vehicle’s safety systems activated. That is often the most powerful evidence in a liability dispute.
The critical limitation: there is no federal regulation requiring motor carriers to maintain or produce ECM data. Unlike RODS records, ECM data has no mandatory retention period under FMCSA rules. ECM data typically overwrites in rolling cycles, in some systems as short as 30 days. If a preservation letter is not sent immediately, this data can be legally destroyed before a lawsuit is ever filed.
The FMCSA’s ELD mandate (49 C.F.R. Part 395, Subpart B) requires the use of a registered, compliant ELD for all interstate commercial motor vehicle drivers who are required to prepare records of duty status.
Most commercial 18-wheelers operating in interstate commerce fall within this requirement. General compliance was required as of December 18, 2017.
Exemptions under federal regulation include:
For a long-haul 18-wheeler operating across Louisiana and Texas, the type of truck most commonly involved in catastrophic collisions, ELD compliance is the rule, not the exception. The most relevant exemption to watch for in litigation is the pre-2000 vehicle exemption, which can apply to older trucks still in service.
Federal regulations set a floor, not a ceiling, on record retention. Under 49 C.F.R. § 395.8(k)(1), motor carriers must retain records of duty status, including ELD data, for a minimum of six months from the date of receipt. ELD data is also subject to the non-alteration requirements of 49 C.F.R. § 395.30.
The six-month period is a floor. It does not mean trucking companies are entitled to destroy records at the six-month mark if they know litigation is pending or reasonably anticipated. Once a carrier has notice that a crash may result in a claim or lawsuit, the general civil discovery rules, and Louisiana’s evidence preservation doctrine, impose an obligation to retain relevant records regardless of when the regulatory minimum expires.
For ECM data, there is no FMCSA-mandated retention period at all. Absent a timely preservation demand or litigation hold notice from the plaintiff (spoliation letter), the carrier has no automatic obligation under Louisiana law to preserve ECM data simply because an accident occurred. Most carriers will destroy this electronic record at the first legally permissible moment.
Under Louisiana jurisprudence, the duty to preserve evidence arises when one of the following conditions is met:
Louisiana does not recognize a standalone tort claim for negligent destruction of evidence. If a carrier destroys data without one of those triggers in place, the remedy is not a separate lawsuit; it is an adverse inference instruction at trial. That instruction asks the jury to presume the destroyed evidence contained information detrimental to the party who destroyed it.
If a preservation letter has been sent and the carrier then destroys evidence, the adverse inference instruction becomes available and can be powerful. But the letter must come first.
What to do immediately after an 18-wheeler accident:
The most time-sensitive action is sending a written preservation letter, often called a spoliation letter or litigation hold letter, to the trucking company and the truck’s owner as early as possible after the crash. This letter should demand the preservation of all ELD data for the driver and truck; ECM/black box data for the truck; GPS tracking data, dashcam footage, driver qualification files, drug and alcohol testing records, vehicle inspection reports, maintenance records, and all communications related to the trip.
An attorney can prepare and send this letter within days of the accident. Once it is sent, the carrier’s legal obligation to preserve that evidence is established.
Was someone you love injured or killed in an 18-wheeler crash? The digital evidence in that truck, which includes speed data, brake data, and hours-of-service logs, may be the proof you need. But it disappears fast. Call the Ikerd Law Firm at (337) 366-8994 or contact us online for a free consultation. We handle trucking cases throughout Louisiana and Texas.
Federal law requires motor carriers to conduct mandatory post-accident drug and alcohol testing under specific circumstances. Under 49 C.F.R. § 382.303, a driver must be tested:
Time is the enemy for these tests. Alcohol testing must be attempted as soon as practicable. If the carrier does not administer the test within two hours of the accident, they must prepare and maintain a record explaining the delay. If they fail to test within eight hours, they must cease all attempts and document the failure. For controlled substances (drugs), the carrier has a strict 32-hour window from the time of the accident to complete the test. If a citation is issued late in that window, the carrier has very little time to act. If they fail to administer the drug test within 32 hours, they must cease all attempts and document their failure. These documented failures to test are crucial evidence of safety-rule violations in litigation.
In fatality cases, mandatory testing applies regardless of whether the driver appears to be at fault. If the carrier did not comply with § 382.303, that failure should be addressed through discovery.
The FMCSA’s Compliance, Safety, Accountability (CSA) program maintains publicly available safety data on every registered motor carrier.
The Safety Measurement System (SMS) scores carriers in seven Behavior Analysis and Safety Improvement Categories (BASICs): Unsafe Driving, Hours-of-Service Compliance, Driver Fitness, Controlled Substances/Alcohol, Vehicle Maintenance, Hazardous Materials Compliance, and Crash Indicator.
In litigation, CSA data serves two purposes. First, elevated scores in relevant BASICs can direct discovery toward the carrier’s underlying inspection violations, the granular roadside inspection records that are the actual admissible evidence. Second, a pattern of serious safety violations in the same category as the conduct causing the crash can support the argument that the carrier had notice of a systemic problem and failed to correct it.
CSA scores are not a fault determination. Courts sometimes limit their direct admissibility. But the underlying inspection data they summarize is a legitimate and often productive avenue of discovery in serious 18-wheeler cases.
IMPORTANT: the SMS data is only good for the last 24 months, at the time it is reviewed. Thus, if you wait to collect it for months or years into litigation, you may not be able to gather information relevant to the company at the time of the subject incident. Check this often during litigation and save the data.
Louisiana’s prescriptive period for personal injury claims was extended from one year to two years for injuries occurring on or after July 1, 2024, under La. C.C. art. 3493.11 (enacted by Act 423 of the 2024 Regular Session). For accidents occurring before July 1, 2024, the former one-year prescriptive period under La. C.C. art. 3492 still applies. Texas also has a two-year statute of limitations law.
Two years may sound like sufficient time. It often is not in a serious trucking case, because the most critical work, which includes preserving the truck’s electronic data, photographing the scene, obtaining the driver’s qualification file, securing the post-accident drug test results, and engaging a trucking expert happens in the first days and weeks after a crash. A Lafayette, Louisiana 18-wheeler attorney who gets involved early can act on all of these fronts while the evidence still exists.
Under Louisiana law, you generally have two years from the date of injury to file a claim for accidents occurring on or after July 1, 2024. Consult an attorney immediately, since deadlines vary based on your circumstances, and critical evidence may be destroyed before the legal deadline arrives.
Case Results Notice: Past results do not guarantee or predict a similar outcome in any future case. Every case is unique. Results depend on the specific facts, evidence, jurisdiction, and legal issues involved. Prior case results are not an indication of future performance.
Call (337) 366-8994 or contact us online for a free consultation.
Most do. Federal law requires ELDs on virtually all interstate commercial trucks built after 1999 and operated by drivers required to log hours of service. Nearly all commercial 18-wheelers also carry ECMs, the on-board computers that record speed, braking, and engine data. Some trucks also carry dashcams and GPS tracking systems with their own data logs. The precise equipment varies by make, model, and the carrier’s internal policies.
If a preservation letter had been sent, overwritten data could give rise to an adverse inference instruction at trial, and the jury could be told to presume the lost data contained information damaging to the carrier. If no letter was sent, the analysis is more complex. An attorney can evaluate whether the carrier had independent notice of potential litigation that should have triggered a preservation duty regardless.
Federal regulation (49 C.F.R. § 395.30) prohibits motor carriers from altering or erasing original ELD data or source data streams. Any edited data must retain the original unedited record alongside it. Unexplained gaps, edited logs, or missing data in an ELD record are significant red flags in litigation and should be investigated with the help of a trucking data expert.
Yes, in most serious cases. Forensic download, preservation, and analysis of ECM data requires specialized equipment and expertise. An accident reconstruction expert or certified electronic data examiner is typically needed to authenticate the data, explain its meaning to a jury, and establish the chain of custody that courts require for electronic evidence.
Both. Federal FMCSA regulations set the safety standards that commercial truck drivers and carriers must meet. Louisiana tort law (and potentially Texas law, depending on where the accident occurred) determines how liability is proven, what damages are available, and how the lawsuit proceeds. Chad Ikerd and the Ikerd Law Firm handle trucking cases in both Louisiana and Texas, including federal court litigation.
An 18-wheeler crash can be devastating, and the evidence proving what happened can be gone within weeks. The Ikerd Law Firm handles serious trucking accident cases throughout Louisiana and Texas, including federal court litigation. Chad Ikerd has obtained a $1.26M federal court verdict in an 18-wheeler case (later settled for $1.45M) and knows how to pursue the full value of what you have lost.
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