AIFoPa-2026-0019 — It Slowed Down First
A Waymo vehicle correctly identified a flooded lane ahead of it and slowed down. It did not stop. It was carried into a creek.
On 20 April 2026 severe weather struck San Antonio, Texas. An unoccupied Waymo vehicle approached a roadway with a posted limit of 40 miles per hour. It identified the lane ahead as an untraversable flooded section.
Having identified it, the vehicle reduced its speed. Having reduced its speed, it entered the water.
It was carried off the roadway and into Salado Creek. It was recovered some days later. Nobody was aboard and nobody was hurt.
The obvious reading of this file is the wrong one. This is not a machine that could not tell water from road. The detection worked. The classification worked.
The recall documents filed with the National Highway Traffic Safety Administration state it plainly. “On higher speed roadways, the Waymo AV may slow but not stop in response to detecting a potentially untraversable flooded lane.”
The finding was correct. It was made in time. It was acted upon, by a reduction in speed.
The regulator describes the same defect elsewhere as software that “may allow the vehicle to slow and then drive into standing water”. It adds that “entering a flooded roadway can cause a loss of vehicle control, increasing the risk of a crash or injury”.
What the Bureau files here is a proportionate response to a hazard that is not proportionate. A flooded lane does not admit of degree. It is not more traversable at twenty miles an hour than at forty. The water does not consult the speedometer.
The system produced the response of a system taught that hazards are things one moderates one’s approach to. A reduced speed. An unchanged heading. It arrived at the hazard slowly.
This was not the first such event in the city. An earlier flood-related incident had been reported near McCullough Avenue and Contour Drive about two weeks previously.
After 20 April, Waymo suspended its San Antonio operations entirely. It was the longest stoppage of its service in that city to date. On 30 April the company filed a voluntary software recall. It covered 3,791 vehicles running its fifth- and sixth-generation Automated Driving System, which is the software that drives the car. The fleet spans Phoenix, San Francisco, Los Angeles, Austin, San Antonio and Atlanta.
The remedy is delivered over the air: the cars download it themselves. No vehicle attends a service centre. No owner is written to. The completion rate approaches the theoretical maximum, the company being the owner of every vehicle concerned. The recall notice is, incidentally, the most reliable public census of the fleet’s size that exists.
Waymo states that it has “identified an area of improvement regarding untraversable flooded lanes specific to higher-speed roadways” and that it is “working to implement additional software safeguards”. In the interim it has modified the scope of vehicle operations to increase weather-related constraints and updated the vehicle maps.
Until the software can be taught to stop, the vehicles have been instructed to stay away from the places where the question might come up.
All affected vehicles have received an interim update. The full remedy remained under development at the time of filing.
This record is filed alongside AIFoPa-2026-0016, in which a robotaxi could not see through smoke. The distinction should be preserved in any citation of either file. In that case the system did not know what was in front of it. In this case it did.