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Reported The Forgotten Constraint Costly
Waymo recalls ADS software after vehicles proceeded past stopped school buses
In a Part 573 safety recall report for NHTSA recall 25E084, Waymo LLC described a defect in its 5th Generation Automated Driving System (ADS) software. Prior to a software remedy, in certain circumstances Waymo vehicles that were stopped or stopping for a school bus with red lights flashing and/or the stop arm extended would proceed again before the bus had deactivated its flashing lights and/or retracted its stop arm. ([recall report](https://static.nhtsa.gov/odi/rcl/2025/RCLRPT-25E084-7732....
A safety rule that is clear for human drivers — remain stopped for a school bus with lights/arm active — was overridden when the ADS’s “don’t impede priority vehicles” logic misfired after a software change, until a hotfix and formal recall restored the constraint.
In a Part 573 safety recall report for NHTSA recall 25E084, Waymo LLC described a defect in its 5th Generation Automated Driving System (ADS) software. Prior to a software remedy, in certain circumstances Waymo vehicles that were stopped or stopping for a school bus with red lights flashing and/or the stop arm extended would proceed again before the bus had deactivated its flashing lights and/or retracted its stop arm. (recall report)
Waymo said the ADS includes features meant to avoid impeding priority vehicles such as public and school buses. After the 20 August 2025 driverless software release (broadly deployed in mid-September 2025), changes to how the system predicted other agents’ intended behavior could lead the ADS, while yielding, to conclude it was impeding a priority vehicle and then proceed when that was not appropriate. The recall covers ADS software from that 20 August 2025 release through software prior to the 5 November 2025 release; Waymo reported 3,067 potentially involved vehicles, all of which it owns. (recall report)
Chronology in the same report: a 22 September 2025 event (slowed to 5 mph, then proceeded before the stop arm retracted) was later identified as the first known instance of this behavior; engineers linked the pattern in October 2025; the Field Safety Committee decided on 30 October 2025 to deploy a hotfix; the update rolled out to affected vehicles between 5 and 17 November 2025; Waymo’s Safety Board decided on 2 December 2025 to conduct a recall. Waymo reported awareness of 12 related citations between 25 September and 14 November 2025, and stated that no collisions occurred related to this behavior. (recall report)
Separately, on 3 December 2025 NHTSA’s Office of Defects Investigation opened Preliminary Evaluation PE25013 into Waymo ADS performance around stopped school buses and compliance with related traffic safety laws, and issued an information request. That letter describes a media-reported incident in which a Waymo AV approached a stopped school bus from a perpendicular side street and passed in front of it while red lights, stop arm, and crossing control arm were deployed, near disembarking students. PE25013 is an opened investigation with information requests, not a completed defect determination. (PE25013 IR)