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Why did the car suddenly accelerate?
Nick - Driven Forensics • 20 November 2023

The journey to find out whether the car accelerated or the driver

The past decade or so has seen a sharp rise in the number of drivers claiming that the cause of their collision, was the vehicle itself. Generally, driver's report that whilst driving, their vehicle unexpectedly and rapidly accelerated which resulted in a collision occurring. It is also not uncommon for driver's state their vehicles brakes failed during the event. This raises various questions, but the first is can a car suddenly accelerate and if so, how common is it and what are some of the possible causes?


Can a car suddenly accelerate on it's own?

Yes a car can suddenly accelerate on it's own and not only is it theoretically possible, there have been instances on modern vehicles where it has already happened. Hyundai recently recalled 38,000 vehicles due to a software fault inducing a sudden and unintended acceleration*. But the problem is not isolated to modern vehicles. Older vehicles are also susceptible to unintended acceleration for a variety of different reasons, such as sticking throttle cables or an external source of fuel being fed to the vehicle's engine.


How common is sudden unintended acceleration?

There are no concrete statistics in the UK to say how common a problem sudden unintended acceleration really is. A Transport for London research paper** from 2021 found that around 16% of bus drivers had suffered a sudden unintended acceleration in their career. Moreover, in the United States, the National Highway Traffic Safety Administration (NHTSA) estimates around 97 people are killed every year as a result of it. The data available or more precisely the lack of data available, might suggest that although not common place, sudden unintended acceleration is still something worth considering when considering a road traffic collision.


What are some of the possible causes?

Generally speaking, the cause of a sudden unintended acceleration is either a defect with the vehicle or an action by the driver. The first I believe speaks for itself, in that there was something mechanically or electrically wrong, which allowed the vehicle to accelerate on it's own. The second, the driver, is slightly more complex. Where you see the term sudden unintended acceleration, you also generally see the term 'pedal confusion'. Pedal confusion generally occurs where a driver depresses the wrong pedal for their intended action, so they press the accelerator instead of the brake or vice versa, and pedal confusion is real.


How can you find out whether the driver or the car accelerated?

The process for determining who (or what) accelerated, starts with a methodical investigation. First of all, where possible, it is important to speak to the driver of the vehicle to obtain their account. What they say may provide investigators with some direction or provide hints as to what caused the incident to occur.


The next step would always be to examine the vehicles or vehicles involved. Through this process you are looking to test the vehicles systems (mechanical and electrical) to determine whether they are working as expected or not.


Finally, it would always be useful to examine any digital data that is contained within the vehicle as this may give some indication as to what happened. The data can come from a range of sources including freeze frame data, dash cameras, third party cameras or even collision data, utilising the Bosch collision data retrieval (Bosch CDR) tool or similar depending on the make of the vehicle. 


How can Driven Forensics help?

Driven Forensics have historically investigated claims of sudden unintended acceleration for insurers, solicitors and privately funded cases. We have the skills, knowledge and expertise to complete the investigation from start to finish. At the start of any investigation, we will always gather as much information as we can about the circumstances, vehicle/s, times, dates, locations and then the specifics relating to the collision. We will develop an investigation plan and follow it through. 


*https://www.autoblog.com/2023/08/28/2021-2023-hyundai-elantra-hybrid-unintended-acceleration-recall/?guccounter=1&guce_referrer=aHR0cHM6Ly93d3cuZ29vZ2xlLmNvbS8&guce_referrer_sig=AQAAAMKSf553uotKTMKqPslZFkO3VOtILIAgMwupQkcxB3EHl1a-1xRbUylvPpl-ZuuJEOXjaJydVT7AePR85CvgNVEW_M2Fvz9mVN5H_K9WyYhSHMdbHBv5z2irUK5lKQQYM3FP-XfUTYXEgvZggeCYMHtiubh9oeYon4Th-UtkRubc

** https://content.tfl.gov.uk/bus-safety-standard-pedal-confusion.pdf

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