Waymo says software glitch caused a driverless traffic jam in Phoenix last month

Last month, a traffic jam clogged up the streets of Downtown Phoenix during “First Friday,” and Phoenix police officers worked to shuffle the stuck vehicles out of the way, but there was a problem: No one was behind the wheel of the dozen cars causing the gridlock. 

It was a likely first of its kind, a slew of driverless white Waymo Jaguars were all stopped in the same place at the same time along Roosevelt Street in Downtown Phoenix. 

“There are 12 Waymos that don’t know what to do and the cops say they can’t tell them where to go,” an unidentified person says in a video posted to TikTok of the incident. 

The incident happened at around 8 p.m. on April 7 at First Street and Roosevelt, according to a Waymo spokesperson. 

“As safety is central to our mission, our autonomous driving technology prioritizes the safest driving path with the information it has at any given moment. Sometimes, that means our vehicle will pull over or come to a stop if it’s assessed to be the safest course of action in that instance, as happened here,” Waymo said in a statement about the incident. “We identified the software that contributed to this situation and made appropriate updates across our fleet within 24 hours.”

But the incident also raises other questions about the Waymo fleet that has been operating on Phoenix streets. 

The most recent report from the National Highway Traffic and Safety Administration listed 12 crashes involving Waymos in the state since July 2021, mainly with the Chrysler Pacifica model of the vehicle. No injuries were reported in any of the accidents. 

The specific model involved in the April 7 incident has been part of Waymo’s fully autonomous taxi service, which can be hailed via an app downloaded to a user’s smartphone. The Arizona Mirror inquired if the jam could have been caused by a user or users calling too many of the vehicles at once, either by accident or for nefarious reasons, and was told that the company prevents this from occurring. 

“This incident was not a result of too many people ordering cars to the same location, as it was caused by software that has since been addressed,” a Waymo spokesperson said. “Under normal operations, our vehicles would look for the most appropriate place to park while waiting for riders to enter the vehicle and start the trip.” 

But what about nefarious actors? 

“My sense is that there are probably ways to disrupt the system if you were creative enough, but certainly not on the level of a conventional DDOS, simply because of the current scale of autonomous vehicle deployment at the moment,” said Andrew Maynard, a professor of advanced technology transitions at Arizona State University’s School for Future of Innovation in Society. 

Maynard said that a DDOS attack, or distributed denial of service attack, would be unlikely given the current way Waymo operates and how the company identifies threats and glitches within its system. 

“I suspect here that autonomous vehicle systems are developing at a measured enough rate that, as they grow, they will be pretty resilient to DDOS-type attacks,” Maynard said. “This doesn’t make them immune, but it does suggest that very disruptive attacks will be challenging (and therefore not worth it to most perpetrators) and quickly addressed.” 

It doesn’t mean that people could still try to create havoc and game the system. 

In 2020, an artist used 99 phones to create a phantom traffic jam in Google Maps, something that theoretically could create problems for self-driving systems like Waymo, which rely on mapping programs like Google Maps. 

Proponents say autonomous vehicles will help ease traffic jams and congestion. 

“In terms of autonomous cars being intended (in part) to avoid traffic jams, there are always going to be unintended outcomes in complex systems, but so far the evidence seems to suggest that (autonomous vehicle) jams are neither widespread or long-lasting,” Maynard said about the relationship between the April 7 incident and the furthering goals of the tech. 

The Phoenix Police Department said it is working with the company to get “extra training” for working with self-driving cars during large events. 

“Coordination was also provided to have a drop-off and pick-up point during large events outside areas where officers were manually directing traffic,” Phoenix Police spokesman Sgt. Brian Bower said. 

Waymo said it plans to maintain a “close relationship” with the Phoenix Police Department and other local law enforcement, and has had a “productive conversation with the Phoenix Police Department on this particular event and how we can continue to coordinate together in the future.” 

Autonomous vehicles have been a regular sight on Arizona roadways since 2015, when Gov. Doug Ducey signed an executive order laying out how autonomous vehicles would be tested in the state, opening the door for companies to begin testing.

Companies like Waymo, Nuro and TuSimple have been testing their vehicles in a variety of capacities on Arizona roads, including on the state’s freeways.

Waymo has also been testing both autonomous semi-trucks along the I-10 corridor between Phoenix and Tucson and a fleet of other autonomous vehicles in the Greater Phoenix area.

The Self-Driving Vehicle Oversight Committee that Ducey created has only met once, in 2016.