Police lights flashing, the cadence of sirens, the ire of a citation this is the rhythm of nightly traffic enforcement. But in San Bruno, California, officers encountered a moment none of them had ever prepared for: a vehicle making an illegal U-turn that stopped dutifully under flashing lights, yet contained no driver behind the wheel.
The car belonged to Waymo, the Alphabet-backed autonomous vehicle company. The officers, conducting a DUI operation, pulled the vehicle over for violating U-turn signage. They rolled down the windows, peered in, and found the cabin empty. The response? They contacted Waymo to report a “glitch.” They could not issue a citation. Their “citation books don’t have a box for ‘robot.’”
What seems like a comedic footnote is in fact a landmark moment at the intersection of autonomous technology, law enforcement, regulation, and public safety. It poses a question only a few years ago looked hypothetical: If a driverless car breaks the law, who is responsible?
The Details of the San Bruno Stop
The incident occurred near the San Bruno Caltrain station, on San Mateo Avenue, where U-turns are prohibited. Officers say a Waymo vehicle executed a U-turn, triggering the stop. The vehicle promptly complied with police signals indicating that many autonomous systems are programmed to yield to emergency lights.
But compliance with the traffic stop did not solve the deeper problem: issuing a ticket. Because there was no human in control, the officers lacked legal standing to issue a moving violation. As the San Bruno Police Department wrote (with a sense of irony): “no driver, no hands, no clue.”
Until July 2026, California law does not permit officers to issue moving violations against autonomous vehicles. Instead, new legislation will allow officers to file notices of noncompliance directed to the vehicle manufacturer.
Thus, for now, when a robot misbehaves on public roads, law enforcement is largely powerless.
The Legal Vacuum Around Autonomous Liability
This San Bruno episode shines a harsh light on how current traffic laws presume a human at the wheel. Traditional statutes assign responsibility to drivers or passengers; cars are legal assets but not decision-makers. Autonomous vehicles break that premise.
In this legal vacuum:
-
No person to ticket — Without a driver, issuing a moving violation becomes legally unsound under current code.
-
No clear accountability — Obligations toward safety shift from individuals to companies, but enforcement mechanisms lag.
-
Regulation lag — Although California’s forthcoming law will empower officers to cite manufacturers, it does not fully address real-time control, accountability for programming decisions, or conditional exemptions.
Lawmakers and regulators must confront whether future traffic laws will treat autonomous vehicles as agents of law, subject to citations, or as equipment whose designers may be penalized for misbehavior.
The Technological Promise vs. Realities
Waymo’s autonomous system, Waymo Driver, is designed to obey traffic rules, detect emergency vehicles, and respond to enforcement direction. The fact that it responded to police signals shows how much programming has anticipated such interactions.
Yet the U-turn violation shows that even well-engineered systems still face edge cases: ambiguous signage, complex intersections, or imperfect sensors. Autonomous systems rely on maps, sensor fusion, and decision heuristics and these can fail.
Waymo itself has experienced past incidents:
-
In June 2024, a Phoenix officer pulled over a driverless Waymo that had driven into oncoming traffic. No citation was issued.
-
In January, one Waymo reportedly drove in circles in a parking lot when malfunctioning.
-
According to Wikipedia, Waymo has logged over 1,218 accidents in autonomous mode, though the majority involve no injury.
These incidents underscore that the margin for error in autonomous navigation remains nontrivial, and regulatory frameworks must catch up.
Law Enforcement Confronts Robot Traffic
The San Bruno stop is just one moment in a broader collision of policing and autonomy. Law enforcement is accustomed to interacting with people, issuing citations, assessing culpability. Robotaxi systems upend all that.
Consider the challenges officers face:
-
Unknown decision chain — When an AV makes a turn or misstep, was it sensor error, software logic, or hardware failure?
-
Delayed oversight — Inspecting logs or black-box data requires cooperation from the manufacturer.
-
Limited real-time control — Officers cannot ask a ghost machine to step out of a vehicle or identify liability in the moment.
-
Public expectations vs. capability — Citizens may demand accountability, but the law currently lacks tools.
Until enforcement protocols evolve, many autonomous missteps will go unpunished or unresolved as with this U-turn incident.
How California is Responding
California is one of the more advanced jurisdictions in managing autonomous vehicles. In response to incidents like San Bruno, the state passed a new law set to take effect July 2026, which allows officers to issue notices of noncompliance directly to companies when autonomous vehicles break rules.
Under the law:
-
Officers may flag violations even without a human driver.
-
Manufacturers must report those violations to the Department of Motor Vehicles within 72 hours.
-
The law also mandates a 24-7 emergency contact for first responders to interact with AV companies in case of incidents.
Yet many questions remain unresolved: How will fines be allocated? Will companies be held criminally liable in extreme cases? How transparent will oversight be?
Ethical and Governance Questions
The San Bruno event raises deeper ethical questions:
-
Should AVs be held to higher standards than human drivers? One might argue that in exchange for safety claims, autonomous systems must operate near-perfectly.
-
Transparency vs. liability — Some systems may not expose full internal logic due to intellectual property concerns, complicating accountability.
-
Risk distribution — Should liability rest with manufacturers, fleet operators, or software designers?
-
Public trust and perception — Incidents like this may erode public confidence: “If robots violate laws and aren’t punished, is the system fair?”
Governance will need to evolve not just technically and legally, but culturally reshaping expectations of road accountability.
What the San Bruno Case Teaches Us
This incident, bizarre though it is, offers valuable lessons:
-
Law needs to catch up with code — Autonomous vehicles are not hypothetical anymore; interactive regulation is required.
-
Edge cases will expose vulnerabilities — Most AV incidents won’t be perfect test conditions; enforcement must account for ambiguity.
-
Manufacturers need accountability pathways — AV firms must build compliance frameworks, reporting channels, and override logic.
-
Public safety demands clarity — Citizens, law enforcement, and regulators must clearly define rights, recourse, and transparency.
Until those elements align, autonomous traffic stops will remain as perplexing as they are headline-grabbing.
The Road Ahead: Policing Autonomy
In the coming years, we can expect:
-
Expanded state and federal laws authorizing enforcement against non-human drivers.
-
Data‐sharing mandates for AV companies to expose incident logs to law enforcement under oversight.
-
Regulatory sandboxes where AV regulation, incident handling, and accountability models are tested.
-
Insurance and liability frameworks shifting to smart policies that cover AV errors.
-
Public education about rights and limits when dealing with AV stops who to call, what records exist.
The San Bruno episode may become a seminal case in legal textbooks about policing autonomous systems.
The Turning Point in Road Law
That night in San Bruno, the police pulled over a car with no driver. The violation was real. The enforcement gap was glaring. The system failed to cite anyone because under today’s law, it couldn’t.
This is the new terrain of mobility. The collision of AI, autonomy, and law is forcing us to rewrite rules that once presumed humans behind every wheel. Whether in San Bruno, San Francisco, or beyond, we are entering a period of tension where regulation, civil authority, and technology all strain toward alignment.
The U-turn wasn’t just illegal it was a turning point.
