Amazon raised some eyebrows last year when it announced future plans to use aerial drones for ultra-fast deliveries to its customers. But in New York City, the company has turned to another delivery route that goes under, not over buildings: the city subway system.

The Financial Times reported Sunday Amazon delivery workers are using the subway to deliver items ordered under the company’s recently launched Prime Now app, which guarantees delivery of certain items within the day. Most New Yorkers can attest that the subway can often be a dramatically faster mode of transportation than driving.  

“In Manhattan, our folks bike, walk or use public transportation,” Amazon representatives told the Financial Times. “They only drive if the item is large like a flat screen TV.”

The Prime Now program is only accessible through a mobile app and available to those who already have a $99 a year Amazon Prime membership. For an additional $7.99 fee, customers can get deliveries of certain items, including things like toilet paper, body wash and electrical cables, within the hour.

Last year Amazon drew attention when it announced plans to have drones deliver orders to customers in 30 minutes or less under a future delivery system. The Federal Aviation Administration’s regulations don’t currently allow that kind of service to exist, but the agency has allowed Amazon to conduct research on drone delivery in the meantime.

Amazon launched the Prime Now program in December in select areas of Brooklyn, Manhattan and Miami. It’s competing with a handful of other localized, fast-track delivery services that have launched in the past year and are aiming to expand, including Google Express, Postmates and Uber’s UberRUSH, all of which promise same-day delivery for certain kinds of purchases. Couriers for those services tend to go by bicycle, on foot or public transportation to get deliveries into customers’ hands.

While same-day delivery services balloon, it’s still unclear whether consumer demand will justify the cost for retailers. A survey released in March by analytics company comScore Inc. found free shipping options drove purchasing decisions for online shoppers around the world: 83 percent of respondents said they were willing to wait an extra two days for their deliveries in exchange for free shipping.