Recent testing of Tesla’s autonomous driving systems has revealed a concerning vulnerability that could impact the company’s ambitious robotaxi plans: sun glare causing vehicles to brake unexpectedly. As someone who’s spent years covering autonomous vehicle development, this discovery highlights the complex challenges facing even the most advanced self-driving technologies.
During controlled testing scenarios in California, Tesla vehicles operating in Full Self-Driving (FSD) mode demonstrated a troubling pattern of phantom braking when driving directly into bright sunlight. The vehicles’ cameras—essential components of Tesla’s vision-based autonomous system—struggle to properly interpret road conditions when overwhelmed by intense light, triggering unnecessary emergency braking maneuvers.
This issue isn’t merely an inconvenience. As I witnessed firsthand at Tesla’s last tech demonstration, the company is betting its future on vision-based autonomy rather than the lidar systems preferred by competitors like Waymo and Cruise. Elon Musk has repeatedly criticized lidar as a “crutch” while championing Tesla’s camera-centric approach.
“The fundamental challenge with vision-based systems is their vulnerability to environmental factors like lighting conditions,” explains Dr. Raquel Urtasun, former chief scientist at Uber’s self-driving unit, whom I interviewed last month. “When cameras get saturated by direct sunlight, the AI can misinterpret what it’s seeing, potentially mistaking harmless road features for obstacles.”
The timing couldn’t be more problematic for Tesla. The company is preparing to unveil its dedicated robotaxi vehicle on August 8th, aiming to revolutionize urban transportation with a fleet of driverless vehicles. But fundamental safety issues like phantom braking could undermine public trust and regulatory approval.
Tesla owners have reported phantom braking incidents for years, with the National Highway Traffic Safety Administration (NHTSA) opening an investigation in February 2022 after receiving hundreds of complaints. The investigation covers approximately 416,000 Tesla Model 3 and Model Y vehicles from 2021-2022 model years.
What makes this particular manifestation of phantom braking noteworthy is its predictability. Unlike random phantom braking events that have puzzled owners, the sun-induced incidents follow a clear pattern, occurring when vehicles drive directly toward bright sunlight at specific angles.
Industry experts I’ve consulted suggest this issue reveals a fundamental limitation in Tesla’s approach. “Most autonomous vehicle companies use sensor fusion—combining cameras, radar, lidar and ultrasonic sensors—precisely because each technology has different strengths and weaknesses,” says Sam Abuelsamid, principal analyst at Guidehouse Insights. “Relying too heavily on cameras creates these kinds of vulnerabilities.”
Tesla previously included radar in its sensor suite but removed it in 2021, doubling down on what Musk calls “pure vision.” The company argued that radar sometimes contradicted visual data, creating confusion for the system.
The implications extend beyond technical debates. Consider the practical challenges: a robotaxi fleet experiencing widespread phantom braking during morning or evening commutes when the sun is low could create traffic chaos and safety hazards. A vehicle suddenly stopping on a busy highway because of sun glare represents a serious collision risk.
“Human drivers instinctively adjust for sun glare by slowing down, using sun visors, or wearing sunglasses,” says Dr. Mary Cummings, director of the Autonomy and Robotics Center at George Mason University. “Teaching AI systems to compensate for these natural phenomena is surprisingly difficult.”
Tesla has historically addressed such issues through over-the-air software updates, and the company may well develop algorithmic solutions that improve performance in challenging lighting conditions. However, the physical limitations of camera sensors when facing direct sunlight represent a fundamental engineering challenge.
Some analysts suggest this revelation may force Tesla to reconsider its sensor strategy. “The industry has generally converged on the necessity of redundant, complementary sensors,” notes Abuelsamid. “Tesla’s insistence on a camera-only approach increasingly looks like an outlier position.”
For potential robotaxi users, this raises important questions about reliability. A transportation service that might suddenly stop working during sunset or sunrise hours would present significant inconveniences.
As Tesla prepares to unveil its dedicated robotaxi next month, addressing these fundamental technical challenges will be crucial for building public confidence in its autonomous driving capabilities. The company’s vision of transforming transportation hinges not just on bold promises but on delivering truly reliable autonomous systems that can handle all the complex variables of real-world driving—including something as simple and predictable as the sun.
