The number of data sources is growing all the time. Many vehicles, particularly those owned by companies, have fleet telematics, insurance black boxes, or dashcam: the list goes on. What has become more relevant over recent months and will continue to grow in the coming months and years is a significant increase in the ability to access data from a vehicle’s event data recorder (EDR). When EDRs are discussed, comparisons are sometimes made to the black boxes installed in aircraft. In reality, EDRs are quite different, but where they matter is that they still assist investigators in understanding what happened in the lead-up to a serious incident.
These devices, which are now fitted to pretty much all cars on the road, provide objective, sometimes time-stamped data that reveals exactly what a vehicle and its driver were doing in the critical seconds before a collision. The ability to obtain and use this data matters to lawyers and insurance for one simple reason: a potentially much earlier view on liability and a potential to reduce cost, shorter timelines whilst also providing a stronger foundation of evidence upon which to base settlement or liability discussions.
What is an EDR?
For vehicles fitted with airbags and seatbelt pre-tensioners, there is a need to ensure fast deployment in the case of an incident. To do this, manufacturers developed specific control modules to decide whether to deploy the airbags. These systems take feeds from around the vehicle and then detect forces that may require deploying an airbag. Where there are minor impacts, like hitting a speed bump a little too hard, the airbag control module (ACM) will detect the impact but will probably decide not to deploy the airbag. This is referred to as a “non-deployment event”. Where the impact is more severe and the ACM decides a safety system, such as an airbag or a pyrotechnic bonnet which protects pedestrians in the case of an impact, should be deployed, this is referred to as a “deployment event”.
In either of these cases (a deployment event or a non-deployment event) the data feeds received by the ACM are stored. This stored data contains evidence about the status of a vast number of vehicle systems, including.
- Vehicle speed (derived from wheel-speed sensors)
- Throttle position (how hard the driver was pressing the accelerator)
- Brake status (on or off, and in some systems, pedal travel or pressure)
- Steering angle (degrees of input)
- Seatbelt status (fastened or unfastened for driver and front passenger)
- Airbag deployment (which airbags fired, and when)
- Longitudinal and lateral accelerations (change in velocity, a proxy for impact severity)
- And potentially much more…
This record survives even if the vehicle's electrical system is damaged or power is lost. With a deployment event, this data is – pretty much – retained indefinitely. Where there is a non-deployment event, this data may be overwritten by other, more recent, non-deployment events. The interesting aspect of these systems is that they may not require a particularly significant impact to record data. I had one such case where a vehicle was impacted by a pedal cycle; the vehicle recorded a non-deployment event, and I could use that data to determine that the vehicle was stationary at the time of the impact.
Since July 2022, EU regulations have mandated that all new passenger vehicle models sold in the EU, and retained in UK law post-Brexit, must be fitted with an EDR. This does not mean every vehicle on UK roads currently has one, but coverage is expanding rapidly. Many vehicles manufactured from the mid-2010s onwards, particularly those from Toyota, Volvo, Volkswagen Group, and BMW, already support EDR downloads using commercially available tools. Many more makes and models are being supported all the time. Once retrieved, the data can be presented in a simple PDF file for interpretation.
How is this data used?
Most systems record five seconds of pre-crash data in half-second increments, providing up to ten discrete data points before impact. Post-crash data varies by manufacturer but commonly includes data that is incredibly useful when reconstructing the collision. The result is a forensic timeline of vehicle behaviour that is difficult to dispute and reasonably straightforward to interpret, provided it is retrieved intact and analysed by a suitably qualified expert.
This data has proved incredibly useful in rear-end collisions where liability can hinge on whether the following driver was maintaining a safe separation or reacted appropriately. EDR data from the struck vehicle can confirm whether brake lights were activated, how heavily the driver braked, and over what period. Data from the following vehicle reveals approach speed, brake application, and whether the driver reacted at all. Where both vehicles' data are available, cross-validation narrows the range of plausible scenarios and exposes inconsistencies in accounts. In one recent motorway case, EDR data confirmed that the claimant had braked to near-full ABS activation 2.5 seconds before impact: an emergency response likely prompted by a hazard ahead. The defendant, in a goods vehicle with inferior braking capability, had insufficient time and distance to avoid a collision. Without the data, the claim would have rested on contested recollections and damage analysis alone.
Its use in insurance fraud cases is also well known. I have reported on cases recently where I have been able to determine which seats were occupied at the time of an incident, disproving an account of a driver attempting to make a fraudulent claim. I have also used EDR to identify a driver who had crashed twice; attempting on the first attempt to set off the airbags but failing to do so, thereafter having a second (and successful) attempt.
How can we use this data to achieve better outcomes?
Despite their growing prevalence, EDRs remain under-utilised in civil litigation and in insurance claims. Many claims handlers and fee-earners are unaware that the data exists, uncertain how to secure it, or unclear on the legal framework governing its retrieval and use. This gap carries a real cost: vehicles are disposed of, modules scrapped, and valuable evidence lost, sometimes within days of an incident. Meanwhile, opposing parties may advance narratives that would not survive scrutiny if objective data were available. The question is no longer whether EDR evidence can assist; t is whether you can afford not to use it. It is the case that due to the increasing costs of storage there is a desire to make quick decisions on vehicle disposal, but that need not be a reason to lose EDR data. The module is about the size of a paperback book, so it can be retrieved and stored for later analysis. Whilst it is always better to have access to the vehicle to retrieve other potential sources of data, it is likely better to have some data than none.
Practical Guidance for lawyers and insurers
The value of EDR data is greatest when it is secured early and analysed by a competent expert. There are a few practical steps that will help, and I would recommend these be considered the moment a claim is notified.
TRIAGE: Triage on notification
When a claim is notified, establish the vehicle make, model, and year. Where the vehicle is new (2024 or newer) there is a very good chance the vehicle will be supported for download, but a quick phone call to an EDR expert will help determine this. Once confirmed that the vehicle is supported for an EDR download, take immediate steps to preserve the module.
PRESERVE: Preserve before disposal
Storage costs understandably drive early salvage decisions. Where a vehicle is likely to be written off, instruct removal and retention of the airbag control module. This costs a fraction of full vehicle storage and ensures the data remains available. Advice can be provided on where the module is situated, but in the vast majority of cases, it is located in the central column between the two front seats, likely just behind the gear lever.
INSTRUCT: Instruct early
Data retrieval is straightforward, but interpretation is less so. Engage a forensic expert with experience analysing this type of data. It is also useful to consider what other types of digital data are available as it is helpful to ensure the expert instructed can use all the available digital data to cross-validate (discussed in the next step). Early instruction allows the expert to advise on what other evidence could be preserved and how EDR data might integrate with CCTV, mechanical inspection, scene evidence, or other forms of digital data.
Once instructed, an expert should treat EDR data as one input, not the complete answer. The strongest reconstructions integrate multiple sources. Where EDR speed is consistent with video analysis, damage profiles, or physical evidence, confidence increases.
Conclusion
In conclusion, Event Data Recorders represent a step-change in the quality of evidence available in personal injury and insurance claims. They provide objective data that narrows disputes, strengthens the reliability of a forensic reconstruction, and informs liability and quantum decisions at the point they matter most. For lawyers and insurers, the question is not whether EDR data is useful, but whether failing to secure it exposes your client to avoidable risk.
The practical barriers are manageable. Coverage is expanding, retrieval is reasonably straightforward, and the cost is modest relative to the evidential gain. What is required is awareness, early triage, and a willingness to instruct competent experts before vehicles are disposed of and evidence is lost.
If you are handling a personal injury or insurance claim involving a road collision, ask three questions: Does the vehicle support an EDR download? Has the module been preserved? And if not, why not? The answers may determine the outcome of your case.
This article first appeared in the Autumn 2025 issue of the MASS insight magazine
About the author
Craig Arnold is a Chartered Forensic Practitioner in road collision investigation. Craig has given expert evidence in criminal, civil, and coroner’s courts on a variety of cases involving catastrophic injuries and fatalities. He specialises in vehicle-borne data and forensic video analysis and has extensive casework experience, including cases in South America, Africa, and Europe. He has a particular interest in new modes of mobility, including connected & autonomous vehicles, and e-scooters.
