This week, federal regulators rolled out new rules for unmanned flying vehicles, in a first step that helps pave the way for drones to start delivering packages to your door. But because of a federal no-fly zone, drones are prohibited in the D.C. area. So the nation's capital is finding a workaround.

In a unanimous vote Thursday, the District of Columbia's city council gave the green light for an Estonian company to start testing its ground-based robot delivery technology right on the sidewalks. The move represents the first time ground-based drones have been approved for testing anywhere in the country, according to the company, Starship Technologies.

"We're really glad that D.C. is one of the primary locations not only in the United States but also in the world for our testing," said Allan Martinson, Starship's chief operating officer, in an interview.

Executives hope their technology will lead to cheap, ground-based delivery service, costing less than $1 per trip. To make that happen, the drones largely eschew the kinds of sophisticated sensors that you'd find in a driverless car or unmanned aerial vehicle.

It's likely that the service will start by field testing the robots themselves for a period before taking any customers. It could take a few weeks to teach the robots how to get around and "get the initial feeling" for the place, said Martinson.

[Driverless delivery robots could be hitting D.C. sidewalks soon]

The city's stamp of approval — passed this week as part of a budget amendment bill — imposes several restrictions. Any company that wants to start testing ground-based delivery drones will be limited to five robots at a time. The robots can't weigh more than 50 pounds unloaded, and they aren't allowed to go faster than 10 miles per hour. If something malfunctions and the robot has to stop in the middle of its route, Starship will need to come along and clear it from the streets within 24 hours.

The pilot project will run from Sept. 15 through the end of December 2017.

Ground-based drones will likely face a number of challenges, from successfully navigating their environments to fending off thieves. But the technology could prove to be an early alternative to drone deliveries, whose future is still hazy despite the Federal Aviation Administration publishing its long-awaited drone rules this week.