Waymo had to recall a similar number last month after it discovered a bug that allowed AVs to drive onto flooded roads.

A new recall notice shows that Waymo is pulling out nearly 3,900 robotaxis from US streets over a software issue that lets autonomous vehicles (AV) enter and drive on closed freeway construction zones.

This comes just a month after the company had to recall a similar number of cars after it found a different bug that allowed its AVs to drive onto flooded roadways.

“Under certain circumstances”, Waymo’s fifth-generation automated driving system software (ADS) could allow AVs to enter and drive “at speed” in freeway construction zones, the safety recall report filed with the US National Highway Traffic Safety Administration (NHTSA) on 17 June read.

The ADS in question is unable to recognise construction zones, or “inappropriately” prioritises avoiding other freeway hazards, the document showed. Waymo said it owned all of the 3,871 robotaxis it is recalling.

Mounting safety concerns alongside political roadblocks hindering its rollout plans in the US are bringing to question whether Waymo – or its competitors – might succeed in enabling wider robotaxi adoption.

Waymo said it began monitoring the latest issue after six separate incidents in April where its robotaxis failed to recognise, and drove past ramp closure signs into pre-planned freeway construction zones in Arizona.

Seven similar incidents in mid-May saw Waymo AVs drive between traffic cones to enter freeway lanes with active construction in the San Francisco Bay Area.  The company decided to recall the cars on 8 June.

“We identified an area of improvement regarding performance around freeway construction zones,” the company said in a statement to news publications. “We voluntarily restricted freeway operations last month while making improvements, proactively notified state and federal regulators and decided to file a voluntary software recall with NHTSA.”

This is the sixth recall Waymo has had to issue for its robotaxis, TechCrunch reported. In December, the company issued a software recall after its AVs drove dangerously around school busses. Other recalls involved low-speed collisions with gates and telephone poles.

Waymo is currently being investigated by the US vehicle safety authority after one of its AVs struck a child near a school in California.

The company also faced a major disruption to services in late December following a massive power outage in San Francisco that stalled its AVs, disrupted traffic and caused a gridlock.

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