Event Data Recorder
Oct 14, 2026Mobility StoriesThey are as much a part of road accidents as tire marks, vehicle parts and conflicting witness statements: the DEKRA accident analysts. Their job is to bring order to the chaos and piece together the clues at the scene into a coherent overall picture. A silent witness, deeply embedded in the vehicle’s technology, can provide valuable clues: the Event Data Recorder (EDR). But does it store the key data from an accident like the black box used in aircraft?
Accident Reconstruction: The Clues Don’t Add Up
The rain is pouring down as the DEKRA accident analysts arrive at the scene. What they find at an intersection near Darmstadt leaves no doubt: a serious road accident has occurred. “As is customary in accidents of this kind, the police called in a DEKRA expert to reconstruct exactly how the collision happened,” explains Katharina Michels, an accident analyst at DEKRA. Since one driver is in the hospital and the other refuses to give a statement, the expert team must work without a witness testimony.
The police officers at the scene quickly agree: both vehicles were traveling in the same direction when the involved car drove too far to the left and the approaching motorcyclist crashed into the driver’s side. But DEKRA’s experts have reason to be skeptical: the final positions of the vehicles do not fit the account of a lane change. A closer look at the vehicle model reveals that the answer may be closer than expected. The reason is the Event Data Recorder (EDR) – a system that records vehicle event data and has been mandatory in the EU for all newly registered passenger cars and light commercial vehicles since 6 July 2024. The rules for heavy commercial vehicles, buses and coaches are being introduced in stages: from January 2026 on, new vehicle types must be fitted with an EDR; from January 2029 on, this will apply to all newly registered vehicles in these classes.
The Event Data Recorder as a Puzzle Piece
Unlike the black box used in aviation, which served as an important model for the EDR, its automotive counterpart does not record conversations inside the vehicle. Instead, key vehicle data such as speed, brake and accelerator pedal position, steering angle, and interventions by ABS and stability control can help reconstruct complex cases accurately. The EDR only saves the relevant data permanently if it registers a change in speed of more than eight kilometers per hour within 150 milliseconds. As a result, minor scratches in a supermarket parking lot are unlikely to be recorded, while actual road accidents can provide crucial data.
Powering Up the Event Data Recorder
Despite the substantial damage to the car, the accident analysts make a fortunate discovery at the scene: the Event Data Recorder remains intact. This is mainly because it is well protected inside the airbag control unit. The accident analysts connect a small readout device to the vehicle’s diagnostic interface and a laptop. With the power supply and ignition still working, they can extract the stored dataset within minutes. Otherwise, the DEKRA team must remove the device at the scene and read it out in the Accident Analysis department. “Because the connector varies from manufacturer to manufacturer, we have built up an extensive collection of cables at our headquarters,” explains Michels.
It is not always easy to pinpoint the moment of impact, because it does not always match the last recorded measuremen
Katharina Michels, Product Specialist in Accident Analysis at DEKRA
EDR Analysis: Every Second Matters
Once there, the most challenging part of the work begins: interpreting the data. For the reconstruction, the crucial point is not the moment of impact but the brief period before it. Michels and her colleagues benefit from an EU-wide framework that requires a dataset covering five seconds, with two measurements per second. “Some manufacturers go even further and provide more data than the legislation requires, such as information about driver assistance systems,” says the mechanical engineer.
The Facets of Accident Analysis: Numbers Tell A Story
Making sense of these figures requires not only a watchful eye but a critical mindset as well. “It is not always easy to pinpoint the moment of impact, because it does not always match the last recorded measurement,” explains the data expert. Measurements can also be inaccurate and, if viewed superficially, quickly lead to false conclusions. This makes it even more important to assess the data alongside traces at the scene, vehicle damage, physical calculations and – where available – witness statements. “A dataset alone does not solve an accident, but it can answer important questions as we clarify the case,” says Michels.
The EDR Alone Is Not Enough: Data Needs Human Judgment
This shows how important human interpretation is. Because the steering-angle data did not support the assumption of a lane change, the expert involved contacted the Accident Analysis department at DEKRA’s head office. There, the responsible experts reviewed the dataset with a motorcycle accident specialist and compared it with the final positions, the pattern of traces and the damage. They then fed their findings into reconstruction software, which visualizes vehicle movements and tests them using physical calculations. The result: the car had apparently made a U-turn; the motorcyclist tried to avoid it and then collided with the side of the car.
The Accident Analysis Report
Based on the accident reconstruction, the DEKRA expert prepares a technical accident-analysis report for the public prosecutor’s office and the court. The key is to explain the technical links clearly enough for people without extensive specialist knowledge to understand them. “We do not determine who is at fault because we are not lawyers,” explains Michels. The defense can inspect the report and, if necessary, question it on technical grounds. If the case goes to trial, the expert explains the report in court. In this case, Michels and her team received the most important news on the day of the accident: the seriously injured motorcyclist survived. “In our work, it is nevertheless important to keep an emotional distance from negative events. In most cases, I manage to do that,” she says.
Why Insurance Companies Look to EDR Data
Although road accidents are among the most common cases in which EDR data are evaluated, DEKRA experts also work for insurers and, in rare cases, even for private vehicle owners. One increasingly common example: with the vehicle owner’s consent, insurers want to find out how an insured vehicle was driven immediately before an accident. Used-car buyers can arrange an EDR readout if they suspect serious damage. “Recently, an older gentleman asked us to read out his vehicle data because he suspected he had confused the accelerator and brake pedals,” says the data expert.
EDR Data and Privacy
Who ultimately owns the data in an Event Data Recorder remains a legal grey area. DEKRA therefore takes no risks: if authorities order a data evaluation after a serious accident, they may seize the vehicle and examine it together with its EDR without the vehicle owner’s consent. If there are no criminal proceedings, however, DEKRA obtains the consent of the vehicle owner concerned.
Data protection is very important at DEKRA. Of course, we understand that such a sensitive issue raises questions
Katharina Michels, Product Specialist in Accident Analysis at DEKRA
Even so, vehicle owners have little to fear: the evaluation relates only to the specific accident. Previously stored events can usually be linked to neither a location nor a time and are thus generally irrelevant to the investigation. The data cannot be deleted or manipulated afterwards legally. “Ultimately, the data is technical, not personal. Unlike with a black box, we are operating at a lower altitude here,” Michels concludes.
Do you need an accident analysis, accident reconstruction or accident-analysis report? DEKRA supports the technical investigation of accident events and the evaluation of relevant vehicle data. More information: https://www.dekra.com/en/accident-reconstruction/
DEKRA Accident Analysis Reports
Reading out control units and event data recorders such as the EDR can form part of an accident-analysis investigation. DEKRA secures traces, surveys accident scenes and reconstructs accident sequences and damage scenarios. Depending on the case, its specialists evaluate data from vehicles, bicycle computers, smartwatches or navigation devices. Computer-assisted run-out and collision analyses, as well as avoidability assessments, complement the technical investigation.
Reading out control units and event data recorders such as the EDR can form part of an accident-analysis investigation. DEKRA secures traces, surveys accident scenes and reconstructs accident sequences and damage scenarios. Depending on the case, its specialists evaluate data from vehicles, bicycle computers, smartwatches or navigation devices. Computer-assisted run-out and collision analyses, as well as avoidability assessments, complement the technical investigation.