The Dramatic Floodwaters Mishap in San Antonio

On April 20, 2026, during a heavy rainstorm in San Antonio, Texas, an unoccupied Waymo robotaxi encountered a flooded section of roadway on a street with a 40 miles per hour speed limit. The autonomous vehicle, equipped with Waymo's advanced fifth or sixth generation Automated Driving System (ADS), detected the standing water but instead of coming to a complete stop, it reduced speed and proceeded forward. Swift-moving floodwaters from Salado Creek overtook the vehicle, sweeping it off the road and into the creek. Emergency crews recovered the robotaxi several days later downstream, with no passengers on board and no injuries reported.

This striking event, captured in reports and sparking widespread discussion, highlighted vulnerabilities in how self-driving cars handle extreme weather conditions. It was not an isolated occurrence; about two weeks earlier, another Waymo vehicle in the same city had navigated through flooded conditions near McCullough Avenue and Contour Drive, prompting initial concerns.

Waymo's Swift Operational Pause

Following the creek incident, Waymo immediately suspended all robotaxi services in San Antonio, marking the company's longest service interruption in the city to date. The pause allowed engineers to review flood detection protocols, weather monitoring systems, and overall safety measures. Operations in other cities like Phoenix, San Francisco, Los Angeles, Austin, and Atlanta continued uninterrupted, but the event underscored the challenges of scaling autonomous ride-hailing in flood-prone regions.

Waymo, a subsidiary of Alphabet Inc., has been expanding its driverless fleet aggressively, surpassing 3,000 vehicles by early 2026. San Antonio represents a key testing ground for the technology amid varied urban and suburban environments.

Details of the Voluntary Recall

Waymo filed a voluntary recall with the National Highway Traffic Safety Administration (NHTSA) on May 6, 2026, under campaign number 26E026. The recall affects 3,791 robotaxis equipped with the fifth and sixth generation ADS, produced between March 17, 2022, and April 20, 2026. These systems enable fully driverless operation, relying on sensors, cameras, lidar, radar, and sophisticated software to navigate roads.

Since Waymo owns and operates its entire fleet directly, no consumer notifications or dealer visits are required. The company estimated that 1% of the affected vehicles exhibited the potential defect. For the complete NHTSA recall report, details outline the scope and response.

Understanding the Technical Flaw

The core issue lies in the ADS software's response to detected hazards on higher-speed roadways. When the system identifies potentially untraversable standing water—using real-time data from environmental sensors—it initiates a slowdown but fails to execute a full stop or reroute aggressively enough. This behavior increases the risk of losing vehicle control in fast-moving currents.

Autonomous Driving Systems like Waymo's integrate multiple layers: perception (detecting water depth and flow), prediction (anticipating risks), planning (choosing paths), and control (executing maneuvers). In this case, the perception module flagged the flood correctly, but the planning module opted for cautionary speed reduction over avoidance, a decision calibrated for typical scenarios but inadequate for flash floods.

• Sensor fusion: Combines lidar for depth mapping, cameras for visual cues, and radar for motion.
• Weather integration: Pulls live data from APIs but may lag in hyper-local flash events.
• Operational design domain (ODD): Limits where vehicles operate, now tightened for flood risks.

Interim Fixes and Long-Term Solutions

Hours after the April 20 incident, Waymo rolled out an over-the-air (OTA) interim remedy to its entire fleet. This included modifying the approved scope of operations to exclude high-risk conditions, such as higher-speed roads during severe weather. Key changes encompassed weather-related operational controls, updated high-definition maps flagging flood-prone areas, and refined extreme weather algorithms.

A permanent software safeguard is under development, focusing on enhanced flood detection thresholds and proactive rerouting. Waymo emphasized its commitment to safety, noting that OTA updates achieve near-100% completion rates since the company controls all vehicles. Service in San Antonio is slated to resume imminently post-review. For in-depth analysis, see this Electrek coverage.

Photo by Hoseung Han on Unsplash

A Pattern of Weather-Related Challenges

This recall follows prior incidents exposing autonomous vehicle limitations in adverse weather. Videos from Phoenix floods in 2025 showed Waymo cars inching through shallow water, raising early alarms. Last December, Waymo recalled over 3,000 vehicles for passing stopped school buses—a separate software glitch fixed OTA. In February 2024, 444 units were recalled after minor collisions with towed objects.

Competitors face similar hurdles: Cruise paused operations after a pedestrian drag in 2023, while Tesla's Full Self-Driving has drawn scrutiny for rain-related errors. These events illustrate the gap between controlled testing and real-world chaos like sudden deluges common in the U.S. Southwest.

Regulatory Oversight and NHTSA's Role

The NHTSA launched a probe into the San Antonio event, prompting Waymo's proactive filing. Unlike traditional recalls involving physical parts, software recalls for AVs emphasize virtual updates, aligning with federal guidelines for emerging tech. The agency monitors over 20 AV makers, prioritizing transparency in incident reporting.

Waymo's safety record remains strong overall, with data showing fewer crashes per mile than human drivers. However, edge cases like floods test regulatory frameworks, potentially spurring new standards for weather resilience. Additional insights appear in CNBC's reporting.

Public Reactions and Social Media Buzz

News of the creek sweep went viral, with Reddit threads and TikTok videos amplifying skepticism. Users shared past clips of Waymo vehicles wading through puddles, questioning readiness for climate-amplified storms. San Antonio locals expressed mixed views: excitement for innovative transport tempered by safety fears in a city prone to flash floods.

Waymo riders in other markets praised reliability, but incidents fuel broader debates on trusting machines in unpredictable conditions. Polls indicate growing comfort with robotaxis, yet weather mishaps erode confidence.

Expert Perspectives on AV Safety

Industry analysts view the recall as a positive sign of Waymo's self-reporting culture, contrasting with less transparent rivals. Philip Koopman, Carnegie Mellon AV expert, notes that floods represent rare but high-risk scenarios, solvable via better sensor fusion and simulation training. Missy Cummings, Duke University human-factors specialist, stresses validating software against diverse U.S. climates.

Proponents argue AVs excel in routine driving, reducing 90% of human-error crashes. Critics highlight liability: who pays if a robotaxi floods?

Implications for the Robotaxi Industry

Waymo's fleet doubling to nearly 4,000 signals booming demand, valued at billions. The recall minimally disrupts expansion plans—Miami, Orlando, Nashville, Portland, and London await. Alphabet's investment tops $10 billion, betting on AV supremacy.

Rivals like Zoox, Motional, and Tesla Robotaxi eye similar scales. This event accelerates industry-wide focus on hydrological mapping and AI robustness against water hazards.

Photo by Leo_Visions on Unsplash

Looking Ahead: Safer Skies for Self-Driving

Waymo's rapid response exemplifies AV evolution: iterative software trumps hardware rigidity. Future fixes may integrate drone feeds, community flood cams, and predictive AI using NOAA data. As climate change intensifies storms, resilient AVs could save lives via precise evacuations.

For riders, enhanced transparency builds trust. The road ahead promises fewer mishaps, propelling robotaxis toward ubiquity while navigating nature's curveballs.