In October 2015, Regina Múrmura, 70, and her husband, Francisco, 69, followed directions on their Waze navigation app into the Caramujo favela, what news reports called a “violent” Brazilian neighborhood 15 miles outside Rio de Janeiro. As their silver Citroen drove through the unfamiliar area, shots—a hail of them—flew through the car. Regina died at the hospital. Francisco was reportedly saved by a pair of silver candlesticks in the trunk that deflected bullets away from his body.

The death of Regina Múrmura made national headlines, firming up the city's reputation for violent crime. Waze is about to launch new feature aimed at preventing similar deaths. On Wednesday, just in time for the Olympics, the company will release Crime Risk Alerts in Rio. Here's how it works: If a user enters an address in one of the 25__ __areas Waze identifies “high crime," they'll see an alert on their screen. “Caution,” it will read, a red exclamation mark hovering above. “This destination is an area with a higher chance of crime.” Users will also get an alert if they happen to drive through one of these areas on their way somewhere else. These locations are areas with higher-than-average homicide, car robbery, or drug trafficking rates. They've been identified by data sources, and corroborated by researchers and Waze map editors on the ground.

Waze had already been considering instituting these pop-up alerts for two years when Múrmura died. And though the company says its decision to implement the feature had nothing to do with the incident, Waze says the community of roughly 2,000 Brazilian volunteers who work on fact-checking their local maps had been asking for such a feature. “It is very easy to get turned around in Rio,” says Paulo Cabral, a Brazil native and Waze’s head of Latin American growth. “I understand the anxiety of ending up somewhere you didn't plan to be.”

Waze

Still, the application sets off alarm bells. (Sorry.) Homicide rates in the Brazilian city have actually declined since 2007, from 37.8 deaths per 100,000 residents to 18.6, though Waze says they're up since last year. Waze's Brazilian users—particularly those who are visiting from nearby cities—may find this feature reassuring. But many "high crime" areas are also poor areas, and some might find it offensive that there's an app that will steer you and your fancy smartphone away from low-income neighborhoods. Do "Crime Risk Alerts" simply feed anxieties about local crime? Or can they actually keep people safe?

Will It Keep You Safe?

To determine which areas get “high crime” alerts, Waze uses data from Disque Denuncia, a Brazilian phone service that receives and logs crime information from anonymous callers. The app supplements those numbers with data from local universities and researchers. Waze cross-references high-crime areas with places where their Rio users often drive, and throws those out—drivers are clearly comfortable with the level of risk in those areas. 25 “polygons” remain—areas as small as a city block or as large as an entire neighborhood.

The company declined to name the communities it’s labeled as “high crime," partly out of respect to those who actually live there. If a user *does *happen to set one of these areas as “home” in her app, she’ll only receive the alert once.

The feature's ability to protect its users will, of course, depend on the quality of the data powering it. And Disque Denuncia data isn't perfect, says Nick Barnes, a doctoral candidate in political science at the University of Wisconsin, Madison, who works with the service’s dataset regularly. “A lot of people use the Disque Denuncia hotline because it’s anonymous,” Barnes says. He says that means the data mostly reflects crime in Rio’s favelas, where people may be afraid to go on the record with notoriously corrupt police. Many of these places are unquestionably dangerous for outsiders. But especially given Waze’s well-meaning attempt to exclude areas already frequented by its users, it may be discarding places where users can still fall victim to crime. Waze says it makes up for these discrepancies with additional data sources. Still, it's TBD whether the new feature will prevent crime, or just make drivers feel more secure in their cars.

Is It Good?

And there are the politics of it all. “I wonder what people in Los Angeles and New York would say [if the feature came there],” says Christopher Gaffney, a geographer with the University of Zurich who studies mega-events in Brazil. It might have. In 2012, Microsoft claimed a patent for a "Pedestrian Route Production" navigation feature, that promised to only take "the user through neighborhoods with violent crime statistics below a certain threshold." Commentators worried the technology would just confirm assumptions about class and race in America—that poor, black neighborhoods are also rife with crime. The patent never turned into a real-life feature.

Waze says it did not consider the racial makeup of its "high crime" areas when it outlined its polygons. But the app could still end up lumping greater stigma on already poverty-stricken areas. What happens when a friend offers to pick another up, only to discover that the passenger-to-be lives in a "high crime" area? What does that do to a relationship—and the night's plans?

Waze has to walk a fine line, between keeping its users safe and being fair to the rest of the country. It's an American-owned company, founded in Israel, trying to create a hyper-local applications for a voracious Brazilian user base—one that's not necessarily representative of all Cariocas. The company insists providing this type of feature "comes back to the moral responsibility we have to promote safety and care for people by highlighting information that we may have at our disposal,” says Julie Mossler, Waze’s brand head. And Brazil is not the only country getting special applications. In May, Waze activated a feature in Los Angeles that automatically reroutes drivers away from left turns across multiple lanes of traffic. It's another tweak in the name of safety; it can also be turned off.

It's up to Waze to determine the limits of its efforts to keep its users safe. Right now, the feature will be confined to Brazil. But this could herald a new type of routing application, one that's intensely personalized but also laden with value judgments. Just like their makers, and the maps on which they're based, all applications are biased. They emphasize some things, downplay others. Users will tell them which ones they find acceptable. In a world where applications' effects go well beyond the smartphone screen (see Pokemon Go), non-users might too.