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Stanford studies human impact when self-driving car returns control to driver
Researchers involved with the Stanford University Dynamic Design Lab have completed a study that examines how human drivers respond when an autonomous driving system returns control of a car to them. The Lab’s mission, according to its website, is to “study the design and control of motion, especially as it relates to cars and vehicle safety. Our research blends analytical approaches to vehicle dynamics and control together with experiments in a variety of test vehicles and a healthy appreciation for the talents and demands of human drivers.” The results of the study were published on December 6 in the first edition of the journal Science Robotics.
Holly Russell, lead author of study and former graduate student at the Dynamic Design Lab says, “Many people have been doing research on paying attention and situation awareness. That’s very important. But, in addition, there is this physical change and we need to acknowledge that people’s performance might not be at its peak if they haven’t actively been participating in the driving.”
The report emphasizes that the DDL’s autonomous driving program is its own proprietary system and is not intended to mimic any particular autonomous driving system currently available from any automobile manufacturer, such as Tesla’s Autopilot.
The study found that the period of time known as “the handoff” — when the computer returns control of a car to a human driver — can be an especially risky period, especially if the speed of the vehicle has changed since the last time the person had direct control of the car. The amount of steering input required to accurately control a vehicle varies according to speed. Greater input is needed at slower speeds while less movement of the wheel is required at higher speeds.
People learn over time how to steer accurately at all speeds based on experience. But when some time elapses during which the driver is not directly involved in steering the car, the researchers found that drivers require a brief period of adjustment before they can accurately steer the car again. The greater the speed change while the computer is in control, the more erratic the human drivers were in their steering inputs upon resuming control.
“Even knowing about the change, being able to make a plan and do some explicit motor planning for how to compensate, you still saw a very different steering behavior and compromised performance,” said Lene Harbott, co-author of the research and a research associate in the Revs Program at Stanford.
Handoff From Computer to Human
The testing was done on a closed course. The participants drove for 15 seconds on a course that included a straightaway and a lane change. Then they took their hands off the wheel and the car took over, bringing them back to the start. After familiarizing themselves with the course four times, the researchers altered the steering ratio of the cars at the beginning of the next lap. The changes were designed to mimic the different steering inputs required at different speeds. The drivers then went around the course 10 more times.
Even though they were notified of the changes to the steering ratio, the drivers’ steering maneuvers differed significantly from their paths previous to the modifications during those ten laps. At the end, the steering ratios were returned to the original settings and the drivers drove 6 more laps around the course. Again the researchers found the drivers needed a period of adjustment to accurately steer the cars.
The DDL experiment is very similar to a classic neuroscience experiment that assesses motor adaptation. In one version, participants use a hand control to move a cursor on a screen to specific points. The way the cursor moves in response to their control is adjusted during the experiment and they, in turn, change their movements to make the cursor go where they want it to go.
Just as in the driving test, people who take part in the experiment have to adjust to changes in how the controller moves the cursor. They also must adjust a second time if the original response relationship is restored. People can performed this experiment themselves by adjusting the speed of the cursor on their personal computers.
“Even though there are really substantial differences between these classic experiments and the car trials, you can see this basic phenomena of adaptation and then after-effect of adaptation,” says IIana Nisky, another co-author of the study and a senior lecturer at Ben-Gurion University in Israel “What we learn in the laboratory studies of adaptation in neuroscience actually extends to real life.”
In neuroscience this is explained as a difference between explicit and implicit learning, Nisky explains. Even when a person is aware of a change, their implicit motor control is unaware of what that change means and can only figure out how to react through experience.
Federal and state regulators are currently working on guidelines that will apply to Level 5 autonomous cars. What the Stanford research shows is that until full autonomy becomes a reality, the “hand off” moment will represent a period of special risk, not because of any failing on the part of computers but rather because of limitations inherent in the brains of human drivers.
The best way to protect ourselves from that period of risk is to eliminate the “hand off” period entirely by ceding total control of driving to computers as soon as possible.
Tesla launched the slightly larger Model Y L in China last year, and it became a hit in no time. The longer wheelbase, larger interior, and slightly more forgiving legroom area in the Model Y L became a sought-after possibility for U.S. buyers, who have been begging the company for a larger SUV.
Now, Tesla needs it more than ever, especially considering the Model X was discontinued alongside its Model S sibling earlier this year. It looks to be more likely than ever, and based on recent reports, it will fall in line with CEO Elon Musk’s prediction that it would arrive in the United States in late 2026.
Recent reports from Forbes and Not a Tesla App both have indicated Tesla plans to bring the Model Y L to the U.S. this year. The reports cite “credible sources,” and an analyst from AutoForecast Solutions named Sam Fiorani stated that the car would enter production later this year.
Fiorani said:
“China, Australia, and India are supplied by the factory in China, which will not supply vehicles to the U.S. Production of the Model Y L is expected to begin in the U.S. in September, which will lead to sales beginning before the end of 2026.”
Production would take place at Gigafactory Texas.
Additionally, a few Model Y L units have been spotted under wraps in the United States, giving more indication that Tesla plans to bring the vehicle to the U.S. When Tesla is close to launching a vehicle in the U.S., it is not uncommon to see these models with the exact car covers that you see below:
Looks like another Tesla Model Y L was spotted in the U.S.! pic.twitter.com/jhsdkcN5Go
— TESLARATI (@Teslarati) June 26, 2026
It makes sense, especially considering Musk hinted the Model Y L would make it to the U.S. in late 2026, but it was up in the air. The CEO said the advent of self-driving might not warrant a larger SUV coming to the U.S. market specifically.
The problem is, consumers do not want to hear that. They love Tesla’s tech, FSD, and other features, but they need more space for growing families. The Model X is gone, and the most anyone can fit in a Tesla right now is seven people in the seven-seat Model Y. That back row is truly only large enough to fit small children comfortably.
Tesla fans have requested a full-size SUV, and the company has made some hints that it could be in the plans.
The Model Y and Model Y L differ noticeably in size, with the Model Y L being a stretched, six-seat variant designed for great interior room. The Standard Model Y measures approximately 4,790mm in length, 1,982 mm in width with the mirrors folded, 1,624mm in height, and 2,890mm in wheel base.
In contrast, the Model Y L extends to be about 4,969–4,976mm long (roughly 179mm or 7 inches longer), stands 1,668mm tall (+44mm), and features a significantly longer 3,040 mm wheelbase (+150mm), while maintaining the same width.
This elongation primarily benefits rear passenger space and enables a 2+2+2 seating layout with captain’s chairs, though it slightly reduces maximum cargo capacity behind the rearmost seats and adds a bit of overall mass and turning radius. The result is a more spacious family hauler that still shares the core footprint and agile character of the original Model Y.
In a major development that will inevitably strengthen Tesla’s dominant position in the American EV market, Polestar has been effectively banned from selling new vehicles in the United States, starting with the 2027 model year.
The U.S. Department of Commerce denied Polestar authorization under the Connected Vehicle Rule, which prohibits vehicles containing certain connected technologies (Cellular, Wi-Fi, Bluetooth, etc.) linked to China or Russia due to national security risks, including potential data collection on American drivers.
🚨 A Tesla competitor goes down
Polestar will no longer sell new vehicles in the United States starting with the 2027 model year.
The U.S. Department of Commerce denied the brand authorization under the Connected Vehicle Rule, which restricts the sale of cars with software and… pic.twitter.com/TrwnQeoiES
— TESLARATI (@Teslarati) June 25, 2026
Polestar, which is majority-owned by China’s Geely Holding, could not obtain the required exemption despite producing some models domestically.
Polestar confirmed it will sell off any remaining inventory of the Polestar 3 and Polestar 4 models, while continuing service and warranty support for existing customers. No new models or major refreshes will reach U.S. buyers, and the company is pivoting its growth strategy to Europe, where it already generates the vast majority of its sales.
The outcome removes a direct premium EV competitor that had positioned itself as a stylish, performance-oriented alternative to Tesla’s lineup. The Polestar 2 challenged the Model 3, while the Polestar 3 and 4 targeted segments overlapping with the Model Y and upcoming Tesla offerings. Polestar’s U.S. sales had already been sluggish amid intense competition and slower demand, representing just 6 percent of its global volume in the first quarter of 2026.
While Polestar was not on Tesla’s level in the U.S., it still places a dent in the evergrowing field of Tesla competitors in the country, where it has long dominated EV sales.
Tesla faces none of these hurdles. As a U.S.-founded and U.S.-headquartered company with major manufacturing in Fremont, Austin, and Nevada, Tesla’s vehicles are built with compliant domestic and allied supply chains. Its Full Self-Driving technology, over-the-air software updates, and vertically integrated ecosystem were developed entirely in-house without foreign ownership entanglements that trigger national security reviews, at least in the U.S.
Of course, it did face a similar threat in China a few years back:
Elon Musk responds to reports of Tesla ban among China’s military over security concerns
The Connected Vehicle Rule, first advanced under the prior administration and upheld under the current one, is part of a broader U.S. effort to protect the domestic auto industry and critical technology from Chinese influence. High tariffs on Chinese-made EVs and related restrictions have already reshaped the market. Tesla benefits directly: it avoids these barriers while continuing to lead in U.S. EV sales volume, Supercharger network expansion, and energy storage integration.
By clearing Polestar from the new-vehicle playing field, the policy reduces competitive pressure in the premium and performance EV segments where Tesla has invested billions. American consumers seeking cutting-edge electric vehicles now have one fewer option tied to foreign adversaries — and one clearer path to the market leader that has driven the EV transition from the start.
For Tesla, this is more than regulatory relief. It is a strategic tailwind that reinforces its position as America’s premier EV innovator at a time when domestic manufacturing and technological independence matter most.
Tesla Cybercab stands to gain from new rules that the Trump Administration is aiming to enforce on autonomous vehicles. On Thursday, NHTSA, under the Trump Administration’s U.S. Department of Transportation, commenced rulemaking on the Federal Motor Vehicle Safety Standards (FMVSS).
This effort aims to eliminate the mandate for manual brake pedals in vehicles that are designed to be driven exclusively by automated driving systems. This would impact the Tesla Cybercab, which the company has stated would operate without a steering wheel or pedals.
Tesla Cybercab launch is imminent after latest sighting at Giga Texas
The Trump Administration is looking to revise FMVSS No. 135, which requires standard braking systems on light-duty vehicles.
Currently, the regulation requires light-duty cars to use traditional manual braking systems that allow operators to slow the vehicle. With the advent of self-driving in the U.S., these regulations need updating, and these are the changes that could come to FMVSS No. 135:
- Removes requirements for hand- or foot-operated brake controls for vehicles designed never to be operated by a human. Existing rules still apply to AVs that retain manual controls.
- All subject vehicles must still meet the same stopping distance performance criteria via alternative testing procedures.
- While this update ensures AVs can physically stop when commanded, NHTSA is separately developing safety performance requirements for AVs in real-world driving scenarios.
- NHTSA will continue to use its broad defect enforcement authority to investigate unsafe ADS behavior and oversee recalls.
As autonomy becomes a greater part of passenger travel, these types of rule adjustments will be more than reasonable. It will give manufacturers the ability to self-certify their vehicles and avoid any red tape that could ultimately delay the deployment of these vehicles.
Administrators are also incredibly excited about the opportunity to play a role in the advancement of self-driving vehicles.
“We are at the cusp of the greatest technological revolution in vehicle technology since the innovation of the Model T,” NHTSA Administrator Jonathan Morrison said. “If we want America to lead the way, we have to reimagine our regulatory framework. That’s why under Secretary Sean Duffy’s AV Framework, NHTSA is tearing down pointless barriers to innovative designs while strengthening the fundamental safety requirements that matter and holding AV developers accountable for safe performance.”
The Cybercab entered mass production at Gigafactory Texas in April. Tesla ultimately plans to push the vehicle into its Robotaxi fleet, potentially when frameworks like these are established.
Tesla looks keen to bring larger Model Y L to the U.S.
One of Tesla’s biggest threats just got banned in the U.S.
