Why do Waymos keep loitering in front of my house?

When a Waymo pulls up and parks in front of her home on a residential street in West Los Angeles, 10-year-old Morgan rushes to the window.

“The Waymo is home!” she says, calling to her parents, Lisa Delgin and Zach Tucker.

It is by no means the first time a Waymo has come “home” to this particular spot. Last year, a Waymo robotaxi dropped Delgin and Tucker off after a New Year’s Eve party and idled there for several minutes until it took off for the next ride. Since then, Waymos have been parking in that same spot, day after day, sometimes for minutes, sometimes for hours.

“It would always come back here, like a beacon,” Delgin said. “Like it knew there was a spot here that it could take.”

As with Uber rideshares and Bird scooters before them, Waymos are the latest tech transportation innovation to start showing up in people’s lives — and they sometimes cause friction with residents in the cities that become their first markets.

But the AI of it all adds a layer of opacity to these interactions. Confused driverless cars seem to make random stops, their mandatory backup sounds are irritating, and it’s unclear whether they are even beholden to traffic laws, human drivers allege. When it comes to parking in neighborhood spots, some residents are annoyed, and some are unsettled by the always-on cameras and sensors. But most just want to know why their homes or blocks seem to have become unofficial Waymo hubs.

“Of all the blocks…” Delgin wonders. Why hers?

Morgan, for her part, is delighted by the Waymo’s return visits, since she sees it as approval of their family by the robot cars. Her parents have been more curious, so they’ve run some informal experiments.

They’ve learned that it’s not just one Waymo taking the spot, since Tucker has documented the license plates of multiple different vehicles. A Waymo will also only select one of two specific parking spots: directly in front of their home or straddling the property line with their neighbors to the south. Delgin has noticed that if both of those two spots are taken, a Waymo coming through will slow down, but not stop or try to park elsewhere on the street, even for open spots directly in front of, behind, or across the street from their home.

The Delgin / Tucker family is not alone in noticing the repeated presence of a parked Waymo in LA, where the robotaxis have operated since November 2024. A resident of the Pico / Fairfax neighborhood, Tal (who preferred to be identified by her first name), said a Waymo often parks on her street, always in front of an apartment building a few doors down. The Verge has observed a Waymo frequently at the same location on a street in Brentwood. Multiple users on Nextdoor have asked fellow neighbors (or complained) about the phenomenon in neighborhoods across LA, including Palms, Playa del Rey, and Westchester.

The practice has also been ongoing in Arizona, where Waymo has operated since 2020. One Scottsdale family says a Waymo often parks around the corner from their home, which is adjacent to a shopping center. In recent months, Reddit users in Phoenix have documented the robotaxis’ frequent spots, while a 2023 AZCentral article first documented the phenomenon. “How do you stop Waymo from storing cars in front of your house between trips?” asks one Reddit thread.

Whether a human or AI drives a taxi, it makes sense that a car would idle for some time before it’s dispatched on its next ride. But what makes Lisa Delgin’s home or the Pico / Fairfax building a safe haven for the robotaxis, with such apparent specificity? Neighbors have their theories: proximity to high-traffic areas, central locations, a lack of parking restrictions, ample curb space. But none of that accounts for the repeated specificity of the parking choice.

And unfortunately, not even Waymo the company necessarily fully knows the answer.

Can a robot catch a break?

Where does a Waymo go on its downtime? The company acknowledges that street parking may be a part of a Waymo’s daily routine. There are parking depots throughout LA where Waymos get charged and cleaned. But when not in use, the company says that the cars park outside the Waymo lots, too.

“Our vehicles will find appropriate parking spots to wait for short periods between trips, either in Waymo’s parking facilities or on-street parking locations,” Vishay Nihalani, Waymo’s director of product management, said in a statement. Waymo is even participating in a forthcoming study from UC Berkeley and UC Irvine analyzing street parking behavior, and its impact on ride wait times and curb and road congestion, by providing researchers with aggregate / hypothetical data.

Waymo street parking behavior differs from a cab or other rideshare vehicle. After the morning rush, Uber driver / actor Josh Myra heads home, which is naturally where he parks his car when he’s not taking rides. Otherwise, Myra does not make a practice of parking in residential neighborhoods between rides. When he’s not working, he’s parked at home. And if he is looking for rides, he will usually drive around high-traffic areas, a practice known as “deadheading,” since he gets far more ride requests when he’s in motion versus when he’s stopped. Myra said this is typical of most of the Uber drivers he knows.

But if a Waymo isn’t at a depot, or doesn’t need to head to a depot for a charge or service, it’s not necessarily going to act like an Uber driver and chase rides. If Waymo isn’t seeing a high amount of traffic for ride requests, it may choose to park to conserve energy and avoid contributing to traffic, while also ensuring there’s some Waymo coverage in non-high-traffic zones.

“When Waymo vehicles are idle and don’t have charging or maintenance needs, they choose between parking in nearby spots or driving to areas of high demand,” Nihalani said. The Waymos opt to drive to these “high-demand” areas when “they’re likely to quickly receive the next hail.” If high-demand areas have an adequate number of Waymos nearby, the cars may choose to park. “This allows us to best match ride-hailing demand and vehicle supply, while conserving energy and reducing traffic congestion,” Nihalani said.

As for where to pull over, there are a few things that definitively go into Waymo’s parking choices. First is “local parking regulations,” so that includes the actual curb restrictions such as time limits or street sweeping. Next is “the number of our vehicles that are parked in a given area.” If there are already Waymo vehicles servicing that neighborhood, the individual Waymo is likely to move on. And finally, “how long they remain parked.” If they tend to hang out there for long periods of time, that could mean a Waymo might not park in that neighborhood (or spot) in the future, since it indicates there’s not much demand in that area.

The decision to park or head to a depot or a high-traffic zone appears to be a balancing act. If a neighborhood doesn’t have another Waymo nearby, and high-traffic areas are saturated with Waymos, parking in a place with minimal curb restrictions might be the best choice. The curb traffic study supports this: UC Irvine lead researcher on the curb study Michael Hyland said data showed that street parking reduces wait times and road congestion. Although it does, obviously, take up more parking spots.

While Waymo provides general insight into its parking choices, it does not address the specificity of the places its vehicles choose to stop — in front of the same house or apartment building, over and over again.

Waymo acknowledges the specific repeat parking phenomenon, but says that the cars’ AI is making so many dynamic decisions in driving as well as parking — about safety, accessibility, and congestion — that it can’t say why a Waymo selects a spot for idling or parking.

Neither the repetition nor the lack of clarity around the behavior shock Phil Koopman, a Carnegie Mellon professor and autonomous vehicle expert. “A computer just doing exactly the same thing the same way every time should not be a surprise to anyone,” Koopman said. “That’s how computers are.” Essentially, they’re smart enough to find an absolutely optimized parking spot — but not necessarily elastic enough in this instance to choose a nearby spot if the optimal spot is not available, the way a human would.

As for how the computers are arriving at that result, Koopman has another theory. Waymo saying that only the car’s computer really knows why it does what it does leads him to believe that Waymo is using machine learning to direct its curb parking decisions. Machine learning means that Waymo engineers provide the cars with data that allows them to make their own decisions based on that data, rather than provide specific instructions via a human-written algorithm.

“Machine learning looks at statistical information and comes up with an answer, and nobody has any idea how it got there,” Koopman said. “And it seems that they are currently not optimizing to vary the location for whatever reason.”

Waymo does not confirm or deny its use of machine learning, instead saying “several elements go into the vehicles’ determination of where to park,” according to Nihalani.

Koopman says that while Waymo may not have insight into how the cars are arriving at their parking choices, they absolutely understand what it’s basing those decisions on. “They don’t know why it made the decision, but they know what data they’re feeding it,” Koopman said. Where it’s legal to park is certainly in this data, but one Reddit user suspects that Waymos have “designated safe spots” — a suspicion that Koopman shares. However, Waymo does not confirm the existence of such designations, and only says that it prohibits parking in certain places.

Tal, the Pico / Fairfax resident, feels slightly uncomfortable about the constant presence of the Waymo with its always-on cameras; Redditors have expressed similar sentiments. Delgin and Tucker have been mostly amused, though sometimes annoyed by the car taking up a spot. Once, while about to head out on an errand, Delgin even made a quick U-turn back into her street spot when she saw a Waymo coming to block it. This sort of moderate annoyance is the overwhelming sentiment on forums where people raise the issue, too.

Some residents have taken their complaints directly to Waymo, the company says. The thing is, Waymo is not technically doing anything wrong, as long as parking doesn’t exceed three hours. Regarding parking regulations governing Waymo parking, Los Angeles Department of Transportation spokesperson Colin Sweeney cites Los Angeles Municipal Code 80.69.2(b), which says that commercial passenger vehicles under 22 feet must follow the same parking regulations that personal vehicles do, and that they can’t park in the same spot for over three hours.

Neither Tal nor Delgin is sure whether Waymo has overstayed this time limit. But researcher Hyland says that, according to the aggregate / hypothetical data, very rarely did any rideshare vehicle park for more than two hours.

Waymo can, and has, told its vehicles to steer clear of certain spots. Waymo confirmed that it is technically possible to mark a spot as a no-parking zone for Waymo vehicles, which it has done in response to neighbor complaints. The police departments of Los Angeles and Phoenix weren’t able to say whether they had gotten any general “loitering” complaints, as these types of information requests require that inquiries be pinpointed to specific locations.

“We are committed to being good neighbors in the communities we operate in,” Nihalani said. “We have received a few pieces of feedback from neighbors, and have made adjustments accordingly.”

Being a “good neighbor” is all well and good, but not providing clarity into the specific parking behavior could indicate larger problems if it is also using machine learning for other functions.

“[Parking] is not high stakes,” Koopman said. “But companies like to use, ‘Well, the computer just did what it did, we don’t know,’ as an excuse for shirking accountability for decisions that might be somewhat harmful.”

Lately, the Delgin / Tucker family’s Waymo has been around less. Waymo confirms that, while usage fluctuates, it has seen a significant uptick in recent months. So chances to stop and take a breather for the robotaxis might be fewer and farther between as the supply of Waymo’s 500-strong Los Angeles fleet begins to meet Angelenos’ demand. Lisa Delgin just hopes, in the future, a Waymo will be around when she needs it.