Truck accident cases in Illinois involve significantly larger amounts of evidence than typical car accident claims. Trucking companies are required by federal law to maintain extensive records — and they know exactly what is at stake when one of their vehicles is involved in a serious crash. Evidence can disappear quickly if steps are not taken to preserve it. Understanding what evidence exists and how to secure it is critical to building a strong case.

Electronic Logging Device (ELD) Data

Since 2019, most commercial trucks are required to have electronic logging devices that automatically record the driver’s hours of service — when they were driving, on duty, in the sleeper berth, or off duty. ELD data is essential evidence in fatigue-related crashes because it shows whether the driver exceeded maximum driving hours or skipped mandatory rest breaks. However, ELD data can be overwritten or lost if not preserved promptly. A litigation hold letter should be sent to the trucking company immediately after the accident to prevent destruction of this data.

The Truck’s Event Data Recorder (Black Box)

Many commercial trucks are equipped with event data recorders (EDRs), sometimes called black boxes, that capture data about the truck’s speed, braking, throttle position, and other mechanical functions in the seconds before and during a crash. This data can reveal whether the driver was speeding, whether the brakes were applied, and how the truck was being operated at the moment of impact. EDR data can be overwritten by subsequent use of the truck, so preserving it quickly is essential. Your attorney may need to send a spoliation letter or seek a court order to prevent the data from being destroyed.

Driver Qualification and Employment Files

Federal regulations require trucking companies to maintain driver qualification files that include the driver’s application, road test certificate, motor vehicle record, medical examiner’s certificate, prior employer inquiries, and drug and alcohol testing records. These files can reveal whether the driver was properly qualified, whether the company conducted required background checks, and whether there were prior incidents or violations that the company should have acted on. Negligent hiring and supervision claims are often built on information found in these files.

Maintenance and Inspection Records

Trucking companies must document all maintenance performed on their vehicles and retain records of pre-trip and post-trip inspections by drivers. When a crash involves a mechanical failure — such as brake failure, tire blowout, or steering malfunction — these records show whether the truck was properly maintained and whether known deficiencies were addressed before the truck was sent back on the road. Missing or incomplete maintenance records may indicate regulatory violations and support a claim of negligent maintenance. The causes of truck accidents frequently involve maintenance failures that proper recordkeeping would have prevented.

Dashcam, Surveillance, and Traffic Camera Footage

Many commercial trucks now have forward-facing and cab-facing cameras. Nearby businesses and traffic cameras may have captured the accident. This footage can show exactly how the crash occurred and whether the driver was distracted, fatigued, or otherwise negligent. However, video footage from businesses is typically overwritten within 30 to 90 days, and trucking company cameras may be controlled by the company. Prompt action — through preservation letters and, if necessary, subpoenas — is essential to securing this evidence before it disappears.

Drug and Alcohol Testing Results

Federal law requires post-accident drug and alcohol testing of commercial drivers when certain conditions are met — when a fatality occurs, when the driver receives a citation and someone is transported for medical treatment, or when the driver receives a citation and a vehicle is towed from the scene. These test results are critical evidence if impairment contributed to the crash. The testing must occur within specific time windows, and the trucking company’s compliance with testing requirements is itself an area of investigation.

Why Early Investigation Is Essential

Trucking companies often begin their own investigation — and their own evidence preservation decisions — immediately after an accident. They may send investigators to the scene, interview witnesses, and engage defense attorneys within hours of the crash. The steps you take immediately after a truck accident can significantly affect what evidence is available later. Engaging an attorney early ensures that your side is actively preserving evidence and countering the trucking company’s efforts to control the narrative.

Contact a Peoria Truck Accident Attorney

The truck accident lawyers at Parker & Parker act quickly to preserve critical evidence in every truck crash case. We send litigation hold letters, secure ELD and black box data, and begin building your case from day one. Call 309-673-0069 for a free consultation.

If you or a loved one has been injured in a car accident, the our Peoria personal injury team are ready to help you pursue the compensation you deserve.

Critical Evidence in Illinois Truck Accident Cases: What to Preserve and Why