Aftermath of car collision

Why law on access to vehicle ‘black box’ data should change

Image credit: Dreamstime

Making information from cars’ event data recorders more readily available to third parties would help to improve safety on Britain’s roads, according to researchers who are calling for changes in the law.

Introduced in the 1970s and present in most new vehicles manufactured today, event data recorders (EDRs) are the equivalent of a black box, recording a range of data from safety systems fitted to the vehicle in the seconds before, during and after a collision.

In the UK and EU, however, access to the accurate and reliable information an EDR can provide about the driver’s actions is restricted by a lack of up-to-date legislation. Manufacturers aren’t currently required to provide EDR data to authorities, road safety researchers or even vehicle owners.

At transport innovation centre TRL, we’re calling for an update to UK and EU laws governing the accessibility of vehicle event EDR evidence. We believe making it available to authorities, insurers and road safety researchers would improve safety, speed up legal proceedings and save lives.

Why is it important? EDR reports contain a vast amount of information on a vehicle’s movements during the five seconds before a recording is triggered – a period that is usually marginally prior to impact. Data is recorded at half-second intervals and most elements, such as accelerator pedal application and engine rpm, can’t be determined to any reasonable level of accuracy – if at all – using alternative methods.

The table below, taken from an example EDR report, illustrates how the most important information when investigating a collision is generally considered to be the speed (second row) and the service (foot) brake (seventh row). This clearly tells us how fast the vehicle was travelling as well as when the driver responded. 

Vehicle collision data chart

Image credit: TRL

Looking at the table, speed was steadily increasing from 13.7mph at -4.9 seconds (4.9 seconds prior to EDR recording trigger) to 18mph at -1.4 seconds. This is corroborated by the consistent accelerator pedal usage of 29 per cent.

Then, at -0.9 seconds and -0.4 seconds the speed suddenly increases to 22.4 and 31.1mph, respectively. At these two points, accelerator pedal usage increases to 48.5 per cent and then 100 per cent. It’s easy to see that the driver used the accelerator between 1.4 and 0.9 seconds before the trigger, and that no braking occurred prior to the trigger.

The table also shows data such as steering input (11th row), which is particularly useful when investigating a collision where there has been a loss of control, or where a vehicle has left the road. Again, this is something that could not be determined from any other method.

An additional element included in EDR reports is a graph showing the change in speed that the vehicle was subject to during the impact. In the graph below, a vehicle was slowed by 12.0mph over a period of 130 milliseconds. We can use this information to analyse the impact on the occupants of the vehicle, and potentially the injuries they sustained. The graph also has two vertical lines indicating when the airbags and seatbelt pre-tensioners deployed within the vehicle. In this case, the majority of the airbags and pre-tensioners deployed 37ms after the impact.

Vehicle data collision graph

Image credit: TRL

It's clear from these two examples that EDR data is extremely useful and allows collisions to be reconstructed to a greater level of accuracy and with more confidence. Experts within TRL believe that an update to the legislation regarding access to it is long overdue. The advantage of EDRs is that they are already installed in the car; it’s simply a case of being able to access the data – something that is already governed by legislation in the US.

Though it must be analysed by a qualified expert, EDR data will be vital as both autonomy in vehicles increases and driverless vehicles become more commonplace, to understand the in-vehicle safety systems and what the driving automation system or a safety driver was doing prior to a collision.

Restricted access to EDR data delays investigations and legal proceedings. Having access to it would make a significant difference to an investigation as it is definitive, conclusive and removes the reliance on assumptions. It’s important in road traffic collision investigations that we promote safety and access to justice, more so than determining fault. We need to know what happened and why, and EDR data greatly assists with this.

Legislation in the UK needs to be reviewed, and a minimum standard agreed upon, to allow controlled access by appropriate third parties such as police, insurers, courthouses and road safety researchers to the EDR data. This would improve experts’ understanding of the cause of collisions and provide significant benefits to safety by advancing future vehicle design.

Dean Beaumont is with the Investigations Group at TRL.

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