The first autonomous robots to deliver packages straight to your front door won’t be flying — they’ll be rolling around on six wheels.

Starship Technologies, an Estonia-based startup created by two Skype co-founders, Janus Friis and Ahti Heinla, is slated to begin testing its autonomous delivery robot to bring groceries and restaurant takeout to Washington, D.C., homes and businesses this fall. It’s the first U.S. municipality to approve ground-based robots to roll around on city sidewalks.

Starship hopes to solve the “last mile” problem –– the work of getting packages from the fulfillment center directly to people’s homes — currently done by humans. It’s a problem Amazon wants to solve with drones, but the FAA’s rules bar drones from flying around humans without an operator in line of sight. But with ground-based delivery, Starship’s founders say, there’s less that can go wrong.

Starship is now touring the United States to look for more cities that will let their robots roam. After a pitstop in San Francisco this week, however, the Department of Public Works decided the city is not ready to fully open its corridors to unmanned machines, opting to charge Starship $66 per side of a city block for a permit, the San Francisco Chronicle reported.

The rules passed in Washington require any company that wants to test ground robots ensure they don’t exceed 10 miles per hour. Starship’s robots max out at four miles per hour and are about the size of a suitcase, designed to carry a payload of around 40 pounds. That’s about three grocery bags.

The Skype co-founders aren’t the only ones promising to ferry robots to your front door. There’s also Dispatch, a San Francisco-based company hoping to bring on-demand, human-free delivery to American streets, but they’re not ready to hit the pavement just yet.

Starship’s rovers can only roam two miles from their original destination, so the plan is to distribute the robots from a delivery van. The company partnered with Mercedes-Benz to create a prototype dubbed “Robovan” that will drive from the fulfillment center to a central destination where the robots will then unload and travel the last mile.

Humans will be on hand to take over in case something goes wrong, monitoring from a remote ground control location with access to the bot’s camera feed. Starship robots are already in action in Europe, where they prowl London for the food delivery companies Just Eat and Pronto. The national postal service in Switzerland is also trying Starship’s autonomous delivery system.

So far, Starship says no one has tried to steal or damage their knee-high machines and that pedestrians tend to just step aside. But Americans may not be as polite. A robot that successfully traversed Canada and Germany was destroyed in Philadelphia last year, only a few weeks into the American leg of its tour.