(Mark Lennihan/AP)

First came in-home delivery. Now Amazon is offering to drop off packages straight to the trunk of your parked car.

The online giant on Tuesday announced that delivery workers will now be able to place packages in certain vehicles parked at homes, offices and other publicly accessible areas. The service is available to Prime members in 37 cities, including Washington and Seattle, who drive Chevrolet, Buick, GMC and Cadillac cars with an active OnStar account, as well as Volvos with an active Volvo On Call account.

The program is the latest effort by the online behemoth to make it easier for customers to receive online orders. Package theft has long been a persistent problem for online shoppers, and Amazon says in-car delivery is one way to combat the problem. But privacy and legal experts say in-car delivery raises a number of concerns about consumer data, and the ways Amazon can use that information to draw conclusions about shoppers and their habits. As with in-home delivery, shoppers may be concerned about letting a stranger into their vehicle.

“Amazon has a voracious appetite for people’s information, and this is one more example of its breathless rush to grab every piece of data and turn it into new forms of revenue,” said Jeffrey Chester, executive director of the Center for Digital Democracy, a Washington nonprofit group.

In November, the company launched Amazon Key, a service that relies on a home-security camera and smart lock to allow couriers into shoppers’ homes to deliver packages. Rival Walmart last year announced a similar program in which delivery workers could bring groceries into shoppers’ kitchens and unload them into their refrigerators, even if nobody is home. (Jeffrey P. Bezos, the founder and chief executive of Amazon, also owns The Washington Post.)

“Amazon’s tentacles are everywhere,” Chester said. “What kind of car do you drive? Where is it parked? What do you have in the back seat? And in which ways will Amazon use that data to market products to you, especially now that they’re getting into ancillary products like life insurance and health insurance?” (An Amazon spokeswoman says the company does not take photos of the car, and that Amazon Key only obtains a customer’s vehicle information on the day of delivery.)

This is how it works: Prime members with the Amazon Key app can link their car to their accounts and select “in-car” delivery during checkout. On delivery day, Amazon gives customers a four-hour delivery window and directs couriers to the parked car, which is unlocked following an encrypted authentication process. The car is relocked after delivery, and consumers receive real-time updates on their phones.

The new delivery service to cars gives customers the “same peace of mind” as in-home delivery with Amazon Key, Peter Larsen, Amazon’s vice president of delivery technology, said in a statement.

The service comes as smart cities and connected cars become more commonplace around the country. After all, some experts say, many drivers now pay parking meters using an app on their phones, and rely on navigational services that know their location at any given time.

“If you trust Amazon with your data, as many people do, then delivery to the trunk of your car is a safe way to getting your package, and perhaps safer than in-home delivery,” said Albert Gidari, director of privacy at the Center for Internet and Society at Stanford Law School. “This is another example of trading off privacy and security for convenience.”

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