Waymo has released a software upgrade for its fleet of nearly 4,000 vehicles to assist them in evading flooded streets as a component of a recall declared by the National Highway Traffic Safety Administration (NHTSA) on Tuesday.

However, the company has not completely addressed the issue regarding how its vehicles respond in these situations. Documents provided by NHTSA indicate that Waymo is still “developing the final solution for this recall.”

The concern seems to be that Waymo’s robotaxis were decelerating but not halting when they encountered flooded roads that were impassable, according to the NHTSA. Robotaxis utilizing both Waymo’s fifth- and sixth-generation autonomous driving systems are involved.

The regulator noted that the recall pertains to 3,791 vehicles — giving us a clearer picture of how many vehicles Waymo operates on the streets across approximately a dozen U.S. cities.

Waymo has now initiated several recalls for its self-driving vehicles. The company’s first recall occurred in February 2024 when it found two robotaxis in Phoenix had independently crashed into the same towed vehicle. Since then, Waymo has conducted recalls to rectify low-speed collisions with parking barriers and telephone poles, as well as to tackle unlawful driving near school buses.

Waymo chose to initiate the recall in late April after its robotaxis had difficulty navigating floods in central Texas; during one incident, an empty robotaxi was carried away in San Antonio. The company has also halted operations in the city.

The initial update sent to its fleet imposes “restrictions at times and at locations where there is an increased likelihood of encountering a flooded, higher-speed roadway,” according to the NHTSA.

“We have pinpointed an area for enhancement regarding impassable flooded lanes on higher-speed roadways, and have made the choice to submit a voluntary software recall with NHTSA concerning this scenario,” Waymo stated in a release. “We are striving to implement additional software protections and have introduced mitigations, including refining our extreme weather protocols during heavy rain, limiting access to regions where flash flooding could occur.”