An 18-wheeler’s “black box” is usually the truck’s engine control module (ECM), which can record data such as speed, braking, throttle and cruise control use in the moments before a crash. Most commercial trucks also carry an electronic logging device (ELD) that records driving time, location, engine hours and miles, which can show whether the driver was over federal hours-of-service limits. This data can be lost or overwritten, so it is important to demand that it be preserved quickly after a truck accident in Texas.
Key takeaways
- The engine control module can capture speed, braking and throttle data around a hard stop or crash.
- Federal rules require most interstate truck drivers to use ELDs, which automatically record date, time, location, engine hours and miles (49 C.F.R. § 395.26).
- Trucking companies generally only have to keep hours-of-service records for six months (49 C.F.R. § 395.8(k)).
- A prompt preservation letter helps protect this evidence; Texas courts can sanction intentional destruction of evidence.
- Most Texas injury suits must be filed within two years (Tex. Civ. Prac. & Rem. Code § 16.003).
What is an 18-wheeler’s black box?
People use “black box” to describe several different electronic systems on a commercial truck. In a typical truck crash case, the most important are:
- The engine control module (ECM). This computer manages the engine. Many ECMs also store event data, such as a “hard brake” or “last stop” record, when the truck slows suddenly.
- The electronic logging device (ELD). This federally required device tracks the driver’s hours of service.
- Telematics and fleet-tracking systems. Many carriers use GPS tracking, messaging systems and safety platforms that send data to the company in real time.
- Dash cameras. Many fleets now use forward-facing and driver-facing cameras, some of which save video automatically when a crash or hard brake occurs.
What each system records depends on the manufacturer, the settings and the software, so the first step in a case is identifying exactly which devices the truck had.
What data can the engine control module show?
ECM data varies by engine maker, but it often can include:
- Vehicle speed in the seconds before and after a sudden stop.
- Whether and when the brakes were applied.
- Throttle (accelerator) position.
- Whether cruise control was on.
- Clutch use and engine RPM.
- Fault codes showing mechanical or system problems.
- Trip summaries, such as average speed, maximum speed and time spent over a set speed.
This information can be powerful because it is objective. If a trucking company claims its driver was going the speed limit and braked in time, ECM data can confirm or contradict that account. It can also help accident reconstruction experts explain how a crash happened.
Why the data has to be downloaded correctly
ECM data is typically pulled with specialized software and hardware. If the truck is driven again, repaired or scrapped, event data may be overwritten or lost. A careless download can also create disputes about whether the data is accurate. That’s why both sides often want their own experts present when the data is retrieved.
What does the electronic logging device record?
Federal regulations require most commercial drivers who must keep records of duty status to use an ELD. Under 49 C.F.R. § 395.26, an ELD automatically records data elements including the date, time, location information, engine hours, vehicle miles, and identification of the driver, vehicle and motor carrier. FMCSA has explained that ELDs record location at regular intervals while the truck is moving and whenever the driver changes duty status.
Why does that matter? Federal hours-of-service rules limit how long a truck driver can drive and be on duty (49 C.F.R. § 395.3). For property-carrying drivers, that includes an 11-hour driving limit and a 14-hour on-duty window. ELD data can show whether a driver was over those limits, skipped required breaks, or was pressured to keep driving while fatigued.
Supporting documents
Beyond the ELD itself, carriers keep “supporting documents” such as fuel receipts, bills of lading, dispatch records and toll records. Comparing those documents to the ELD can reveal whether the logs were edited or don’t match where the truck really was.
How long does a trucking company have to keep this evidence?
Not long. Under 49 C.F.R. § 395.8(k)(1), motor carriers generally must keep records of duty status and supporting documents for six months. After that, the federal rule no longer requires them to keep the records. ECM event data can disappear even sooner if the truck goes back into service.
The safest step is a written preservation letter (sometimes called a spoliation letter) sent to the trucking company and its insurer as soon as possible after the crash. It typically demands that the company keep:
- The truck and trailer in their post-crash condition, or allow an inspection first.
- ECM, ELD, telematics and camera data.
- Driver logs, dispatch messages and cell phone records.
- Maintenance, inspection and repair records.
- The driver’s qualification file and drug and alcohol testing records.
What if the trucking company destroys evidence?
Texas law addresses this situation through “spoliation” remedies. In Brookshire Bros., Ltd. v. Aldridge, 438 S.W.3d 9 (Tex. 2014), the Texas Supreme Court held that a trial court may instruct the jury it can presume destroyed evidence would have been harmful to the party that destroyed it, but generally only if the party intentionally concealed or destroyed the evidence, or negligently lost it in a way that left the other side irreparably unable to present its case. Because that bar is high, preserving evidence early is far better than trying to prove later that it was wrongfully lost.
Who can get the black box data after a Texas truck crash?
The truck and its data usually belong to the motor carrier or the truck’s owner, not to the people who were hurt. An injured person typically gets access through a preservation demand, an agreed inspection, or formal discovery after a lawsuit is filed. Police may also collect some data during a crash investigation, especially in serious or fatal crashes.
This is one of the ways 18-wheeler accident claims differ from ordinary car vs. truck collisions with a pickup or personal vehicle: there is often far more electronic evidence, and the trucking company and its insurer usually begin their own investigation right away. When a truck crash causes a death, the same evidence is central to a wrongful death claim. For more on how Texas injury claims work, see our Texas injury law guide.
The deadline to sue still applies
Even if the truck data is preserved, you still need to file suit on time. In Texas, personal injury claims generally must be filed within two years after the claim accrues, and wrongful death claims within two years of the date of death (Tex. Civ. Prac. & Rem. Code § 16.003). The six-month record retention period means the practical window to protect key evidence is much shorter than that.
If you or a family member was hurt in a crash with an 18-wheeler, talk to a lawyer about preserving the truck’s data as soon as you can. Borunda & Fomby PLLC is based in Houston and represents injured people throughout Texas. Consultations are free, and you pay no fee unless we win. Call (713) 930-4878 (24/7) or contact us online. Se habla español.
This article is general information about Texas law, not legal advice, and reading it does not create an attorney-client relationship. Every case is different.