Editor’s take: Some riders of robotaxi services have been experiencing harassment from people emboldened by the absence of a human driver. These incidents raise the question of how emergency response protocols can be adapted for autonomous vehicles.

As Alphabet’s Waymo expands its driverless taxi service across major U.S. cities, a new set of challenges is emerging for passengers who find themselves in unexpected and unsettling situations. While the promise of increased safety and convenience has drawn many to these futuristic vehicles, recent incidents have shown that sometimes a human at the wheel is necessary when navigating urban environments.

The Washington Post spoke with several people who experienced harassment while in these vehicles. One person, a tech worker in San Francisco whom the Post identified as Stephanie, initially embraced Waymo’s robotaxis for their perceived safety advantages, particularly for women traveling alone. However, her perspective shifted dramatically after a harrowing experience one Saturday night.

As she and her sister were being driven home, their Waymo vehicle was pursued by a car full of young men who began catcalling and following them closely. The incident left Stephanie feeling vulnerable and wishing for a human driver who could have easily altered the route to evade their pursuers.

The inability to quickly redirect the vehicle’s path in threatening situations has become a significant concern for some Waymo users. Stephanie’s attempts to seek help were frustrated when a 911 dispatcher informed her they couldn’t dispatch police to a moving vehicle.

In another unsettling incident, Elliot, a San Francisco tech worker, found himself face-to-face with a potential assailant who attempted to enter his Waymo vehicle while it was stopped at a red light. The man briefly displayed what appeared to be a knife before walking away. Elliot, who later filed a police report, said he wished that the vehicle could have reacted more swiftly to the threat.

Madelline, a 25-year-old restaurant server, recounted a late-night ride where her Waymo became immobilized due to a road rage incident unfolding ahead. The robotaxi’s adherence to traffic rules left her feeling trapped and anxious as the situation escalated.

Waymo has acknowledged these concerns, noting that they are relatively rare. “We take these events very seriously and understand how upsetting they can be,” company spokesman Ethan Teicher told the Post. Waymo offers support agents who can stay on the line with riders during incidents and work with law enforcement when necessary. Passengers can also use the Waymo app to request the vehicle to pull over or change its destination.

Some users would like further protections, though, such as having greater control over the vehicle’s route, particularly in potentially dangerous situations. And when Stephanie asked Waymo for video footage of the car that had been following her hoping to get the license plate, the company declined to provide it, she said.

Experts in the field of autonomous vehicles are not surprised by these riders’ experiences. Michael Brooks, executive director of the Center for Auto Safety, pointed out to the Post that while robotaxis excel at following traffic rules, they struggle with interpreting and responding to nuanced human behavior. This technological gap has led to situations where vehicles can be easily manipulated or obstructed by pranksters or those with malicious intent.

The solution to these issues likely lies in a combination of improved vehicle sensing capabilities and enhanced coordination with remote operations teams, according to Missy Cummings, an engineering professor at George Mason University. However, Phil Koopman, an electrical and computer engineering professor at Carnegie Mellon University, said there are limits to what autonomous vehicles can be programmed to do, especially when it comes to actions that might violate traffic laws.

Despite these challenges, many riders continue to appreciate the benefits of driverless taxis. Madelline, for instance, still prefers Waymo to human-driven ride-hailing services, citing the comfort of being alone in the vehicle.