California regulators say they are taking a close look at potential safety problems involving General Motors’ robocab subsidiary, Cruise LLC following receipt of an anonymous warning from a company insider.

Cruise recently received approval from state regulators to begin commercial service using its driverless vehicles. But the readiness of the technology has come under question following an embarrassing incident early in which a fleet of robocabs suddenly halted at a busy intersection in San Francisco, blocking traffic for hours.

The letter sent to the California Public Utilities Commission, or CPUC, from someone claiming to be a veteran Cruise employee claimed he and other colleagues “generally do not believe we are ready to launch to the public, but there is fear of admitting this because of expectations from leadership and investors.”

Taking the lead

Cruise is considered one of the leaders in the development of autonomous and fully driverless vehicles, and it has been testing them in public in a number of locations including San Francisco, where it is based. It stole a march over competitors, such as Google spinoff Waymo, when it became the first to receive approval to begin commercial operation using fully driverless vehicles.

But it could face the prospect of having that deployment permit revoked should authorities find it has operated in an unsafe manner.

Questions about the safety of autonomous technology, in general, have surfaced repeatedly in recent years, especially after an Uber prototype struck and killed a pedestrian four years ago in a Phoenix suburb. The National Highway Traffic Safety Administration, meanwhile, raised a caution flag last month when it released a preliminary study revealing there were nearly 400 known crashes involving autonomous and semi-autonomous systems over the prior year.

The majority of those involved vehicles using Tesla’s Autopilot system, though Cruise was one of the others identified in the report.

Mounting concerns

But critics point to other incidents that should raise concerns. Earlier this month, a half-dozen Cruise robotaxis simultaneously malfunctioned at a downtown San Francisco location, some reports suggesting they lost their connection to Cruise’s cloud-based operating system. They brought traffic to a complete halt at the intersection of Gough and Fulton streets for several hours. The driverless vehicles only began moving again when Cruise engineers went to the scene and fiddled with their programming.

Such incidents have occurred “with regularity,” according to the Cruise whistleblower — who described himself as a father and someone working on safety critical systems. Such incidents are known as “VREs” or “Vehicle Retrieval Events.”

“When this occurs,” he explained, “a vehicle is stranded, often in lanes where they are blocking traffic and potentially blocking emergency vehicles. Sometimes it is possible to remotely assist the vehicle with safely pulling over, but there have been some cases where fallback systems have also failed and it was not possible to remotely maneuver the vehicle outside of the lanes they were blocking until they were physically towed from their location to a facility.”

Triggering an investigation

After obtaining a copy of the letter, the Wall Street Journal approached the CPUC. A spokeswoman told the publication that when it receives such a complaint, “We look into the issue to determine validity and whether the entity is adhering to our rules and regulations and take additional regulatory action based on those findings.”

The agency also released a 24-page document explaining the reasoning behind the CPUC’s decision to allow Cruise to begin commercial operations. The agency could revoke or suspend the company’s permit should evidence of safety problems surface.

For its part, Cruise issued a statement after the July incident that shut down traffic in downtown San Francisco. “While it was resolved and no passengers were impacted, we apologize to anyone who was inconvenienced.”

Cruise defends its record

The company responded to the whistleblower report, stating, “Our safety record is tracked, reported, and published by multiple government agencies. We’re proud of it and it speaks for itself.”

Perhaps, but the unidentified employee clearly has a different viewpoint.

“My subjective opinion from experiencing this and speaking with others at the company is that employees generally do not believe we are ready to launch to the public,” he told the CPUC.

While the letter has triggered a closer look at Cruise’s safety and operational record, it has also raised questions about who wrote it. The CPUC has not confirmed whether it has verified if the writer was, indeed, a Cruise employee. And while website TechCrunch reached out after obtaining the e-mail address used to submit the letter, it said it has not yet received a response after reaching out to the whistleblower.