SAN FRANCISCO (AP) — Amazon's latest perk ... free delivery to your car. The Seattle company said Tuesday that it has begun delivering packages in 37 cities to Prime members who own newer General Motors or Volvo vehicles.

The delivery service works when cars are parked in publicly accessible areas, such as on the street in front of an apartment building, at a workplace surface parking lot, or in a home driveway — but not in a private parking garage, for example. Packages can put in the vehicle's trunk or out of plain sight.

Deliveries via the Amazon Key In-Car service are available to Prime members with 2015 year or newer Chevrolet, Buick, GMC or Cadillac vehicles with GM's OnStar connected-car service, and those with a 2015 or newer Volvo vehicle with an active Volvo On Call account.

Amazon Prime customers need to download the Amazon Key app. From there, they can link their connected car and start their Amazon orders. No additional hardware or devices are required.

On the day a package is scheduled for delivery, customers can use the Amazon Key app to check if they've parked within range of the delivery location. The app also provides notifications with the expected 4-hour delivery time window and notifies customers when the delivery is on its way and the package has been delivered. Customers can track when their car was unlocked and relocked through the app, where they can also rate the experience.

"Receiving a package securely and reliably in your car, without you having to be there, is something we think many people will appreciate," said Atif Rafiq, chief digital officer at Volvo Cars. "This mix of car and commerce is starting the next wave of innovation and we intend to be at the forefront."

Amazon said that it will include more locations and more vehicle makes and models over time.

The announcement of the in-car delivery service follows Amazon's introduction of the Amazon Key program last year that lets the people delivering packages into the homes of customers who opt in.

To check eligibility and to sign up for Amazon Key In-Car, visit amazon.com/keyincar .