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Tesla owners accuse their cars of sudden unintended acceleration. Is it true?

NHTSA is considering an investigation into reports of “sudden unintended acceleration” (SUA) in Tesla vehicles. Tesla has responded in a company blog post, denying there’s a problem. Vehicle logs available from Tesla appear to confirm the company’s story, but its detractors say there’s more to it than what Tesla is willing to say.

Do Teslas have a sudden unintended acceleration problem? Here’s the information available so far.

What is sudden unintended acceleration?

Sudden unintended acceleration is when a vehicle suddenly takes off on its own without input from the driver, for a variety of reasons. The problem is rare, and deeper investigation almost always shows the driver was at fault, often because they thought their foot was on the brake when it was on the accelerator.

SUA is rare because federal law requires redundancy. No computer is perfect, but there’s no room for error when lives are at stake, so manufacturers use multiple pedal sensor inputs that must match up. If they don’t, the vehicle’s computer cuts power.

In the case of Toyota, which famously had a SUA crisis that resulted in a recall of more than 2 million vehicles in 2011, the problem had a simple, analog source. The blame was laid on floormats that could slip onto the accelerator. Today, most cars come with clips to hold the driver’s side floormat firmly in place.

Tesla’s log data

Tesla, and at least two independent log analysts, report finding driver fault in the incidents reported. Tesla has repeatedly stated they investigate every allegation of SUA with a Tesla vehicle, and that in every case the logs show that the accelerator pedal was pressed when the vehicle lurched forward.

But what if the pedal wasn’t pressed when the log claims it was?

Dr. Ronald Belt, a retired electronics technician publishing at the Center for Auto Safety, has a history of independently investigating SUA claims. Belt took a detailed look at data from a Tesla Model S that allegedly experienced SUA. The data came second-hand from an owner who obtained the data from Tesla in a phone conversation.

Dr. Belt's graph of pedal activation in Tesla SUA incidents
Belt’s graph of pedal activation in Tesla SUA incidents Image used with permission by copyright holder

The log shows the accelerator pedal was pressed, or more accurately, it shows the voltages expected from an activated accelerator pedal. However, the log also showed something extraordinarily unlikely. Several releases of the accelerator pedal that lasted exactly 1 second.

Belt theorizes the vehicle’s drive unit overheats a sensor during low-speed driving and causes the sensor to leak current. When that happens, Belt says the computer mistakenly responds to a false pedal input and provides power to the electric motors, propelling the vehicle forward into an obstacle. One of the components “resets” repeatedly, cutting the current in inhumanly precise 1-second intervals.

While this theory is plausible, it’s only that. Dr. Belt didn’t have direct access to the vehicle. It proves only the reason why a more through investigation could be helpful. Definitive confirmation of unintended acceleration isn’t possible from afar.

Why the NHTSA is considering an investigation

In late 2019, Brian Sparks of Berkeley, California began looking at media reports and NHTSA reports of SUA in Tesla’s vehicles. Once he had information compiled, he prepared a report for the NHTSA, and petitioned them to investigate the matter. After several months, and a follow-up providing additional data, the NHTSA announced it will look into whether his data warrants a full investigation.

The petition is a 69-page document that catalogs every Tesla-related SUA incident reported since 2013.

Tesla was quick to respond to the NHTSA’s announcement in a company blog post. “This petition is completely false and was brought by a Tesla short-seller. We investigate every single incident where the driver alleges to us that their vehicle accelerated contrary to their input, and in every case where we had the vehicle’s data, we confirmed that the car operated as designed.” Digital Trends reached out to Tesla for further comment, but have yet to receive a response.

Sparks doesn’t deny that he is a Tesla short-seller, but insists he didn’t file the petition for financial gain. “It’s not about shortselling.” Sparks said. “They should really read the petition.”

The petition is a 69-page document that catalogs Tesla-related SUA incidents reported since 2013. In addition to a tally of SUA incidents for each model and year, it includes the descriptions of the incidents as reported by owners, or in the media.

One incident, typical of others in the petition, claims a Tesla vehicle surged forward in a parking lot. The incident was reported by the owner to the NHSTA.

“Vehicle entered a shopping plaza at speed under 10mph and suddenly accelerated to high speed on it’s own. It hit three stationary vehicles and knocked down a small tree. Tried stopping the car but the brakes would not work and the car finally stopped after hitting the third vehicle.”

In most situations compiled by Sparks, the driver was moving at low speed in a parking lot, driveway, or a similar situation. When they stopped, or were about to stop, the driver reports the vehicle suddenly accelerated forward, without the driver pressing on the accelerator.

What’s next for the case?

The information provided by Dr. Belt and Sparks looks compelling, but it’s a long way from proof that Tesla has a sudden acceleration problem. Dr. Belt’s analysis isn’t based off a hands-on investigation of the vehicle that had a problem. Sparks’ statistical analysis finds a high rate of incidents, but can’t pinpoint a specific defect.

What’s next? The NHTSA will decide if it wants to conduct a full investigation. If it does, the agency could gain access to all the logs Tesla collected, as well as vehicles. The NHSTA may even perform its own testing to see if it can replicate sudden unintended acceleration.

Of course, the NHSTA may decide not to investigate, closing the case on Sparks’ petition and vindicating Tesla.

In addition to a possible NHTSA investigation, several Tesla owners filed a lawsuit over the alleged SUA issues with the vehicles. If that case proceeds, more evidence and data could emerge to shed light on the issue.

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