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

The online giant announced Tuesday 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.

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

The program is the latest effort by Amazon 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.

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 using an encrypted authentication process. The car is relocked after delivery, and consumers receive real-time updates on their phones.

But privacy and legal experts said in-car delivery raises concerns about consumer data, such as the type of car you drive, and the ways Amazon can use that data to draw conclusions about shoppers and their habits. And like 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-based nonprofit.

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 get your package, and perhaps safer than in-home delivery,” said Albert Gidari, director of privacy at the Center for Internet & Society at Stanford Law School. “This is another example of trading off privacy and security for convenience.”