Waymo, the autonomous vehicle subsidiary of Alphabet, has issued a recall for its entire fleet of robotaxis operating in the United States following an incident in which one of its vehicles drove into a flooded creek in San Francisco. The recall, announced late on Tuesday, affects approximately 672 vehicles and comes as UK regulators call for a comprehensive safety review of autonomous driving technologies.

The incident occurred on March 15 when a Waymo vehicle, navigating without a human driver, failed to recognise the hazard posed by floodwater from a broken fire hydrant. The car proceeded into the water, becoming submerged and causing extensive damage. No injuries were reported. Waymo’s internal investigation concluded that the vehicle’s perception system misidentified the standing water as a passable surface, a flaw that the company says has now been corrected via a software update.

The recall is classified as a “voluntary safety recall” under US National Highway Traffic Safety Administration (NHTSA) oversight. It is the first such recall for Waymo’s driverless fleet, which has been operating commercially in San Francisco since 2022. The company has stated that all affected vehicles will receive the over-the-air update automatically, with no physical modifications required.

In London, the Centre for Connected and Autonomous Vehicles (CCAV), part of the Department for Transport, issued a statement expressing concern over the incident. “The Waymo event raises serious questions about the robustness of autonomous systems in unpredictable environments,” a CCAV spokesperson said. “We are working with international partners to ensure that safety standards keep pace with deployment.” The CCAV has commissioned an independent review of the risk assessment protocols used by autonomous vehicle operators, with findings expected within six months.

The response from UK regulators reflects broader unease about the rapid expansion of robotaxi services. While no Waymo vehicles operate in Britain, several companies, including Oxa and Wayve, are conducting trials on public roads. The CCAV’s review will inform potential changes to the Automated Vehicles Act, passed in 2023, which is designed to regulate driverless cars without a human supervisor.

Waymo has emphasised that its recall demonstrates the effectiveness of existing oversight mechanisms. “We reported this event to NHTSA promptly and have already deployed a fix,” a Waymo spokesperson said. “Our commitment to transparency and safety remains absolute.” The company insists that its vehicles have logged millions of miles without a comparable incident, and that the flood incident does not indicate a systemic failure.

Nonetheless, critics argue that the incident reveals limitations in AI-driven perception under conditions of “edge case” weather or debris. Professor Sarah Nelson, a specialist in autonomous systems at Imperial College London, said: “The vehicle’s inability to recognise floodwater suggests a gap in training data. Rain, snow, and standing water remain challenging for lidar and camera-based systems.” She added that regulators must establish clear benchmarks for performance in adverse conditions.

The recall has also drawn attention to the legal framework for liability in autonomous vehicle accidents. Under US law, manufacturers are responsible for safety defects, but questions remain about when an incident constitutes a design flaw versus an unforeseeable scenario. In the UK, the Automated Vehicles Act assigns liability to the manufacturer or software developer, but only if the vehicle is operating in “self-driving mode”.

Waymo’s recall follows a series of high-profile incidents involving autonomous vehicles, including a fatal crash involving an Uber self-driving car in 2018 and a collision between a Cruise robotaxi and a bus in 2023. Each case has prompted regulatory scrutiny but has not derailed the industry’s expansion. Waymo, for its part, continues to pursue scaling of its service to additional US cities, including Los Angeles and Austin.

The CCAV’s safety review is expected to propose stricter requirements for real-world testing, including mandatory reporting of near-misses and more robust scenario simulation. UK Transport Minister Michael Ellis has stated that “public trust is non-negotiable” and that the government will not hesitate to tighten rules if necessary.

As the autonomous vehicle industry matures, the balance between innovation and safety remains delicate. Waymo’s recall, while modest in scale, underscores the challenges of deploying machines that must navigate the chaos of real-world environments. For UK regulators, the incident provides a cautionary lesson in the importance of proactive oversight.