– Designers of futuristic cityscapes envision delivery drones dropping off your packages from the sky and driverless cars taking you to work. But the robotic delivery invasion already has arrived in the form of machines that look like beer coolers on wheels scooting along the sidewalks.

The ground-bound robots, developed by the science fiction-sounding company Starship Technologies, will be showing up any day in the nation’s capital and in Redwood City, Calif. They could soon be in up to 10 cities, ferrying groceries and other packages over what the company calls the “last mile,” from a neighborhood delivery “hub” to your front door, all for as little as $1 a trip.

A second company, TeleRetail, plans to test its sidewalk robots in Washington and other cities, including Mountain View, Calif., next year.

Like driverless cars, the delivery robots use cameras, GPS and radar to “see” their urban environment and navigate through it.

The robots are the first of what the companies foresee as a wave of inexpensive, high-tech, electricity-driven alternatives to gasoline car-driven shopping trips and delivery trucks that contribute to traffic gridlock and pollution. Urban futurists see the little robots as an integral part of a digitally based “smart city” landscape — although it will take time for humans to adjust to them, and they come with privacy concerns.

“We think there will be hundreds, if not thousands, of robots on the ground eventually around the world,” said Allan Martinson, chief operating officer of Starship Technologies, based in London and started by the co-founders of internet telephone company Skype.

Torsten Scholl, founder of TeleRetail, which is based in Switzerland, said, “Why have a vehicle as big as an autonomous car to deliver goods? We think of it as a self-driving trunk.”

And tech gadget website Tech Crunch has called autonomous vehicles — like drones, driverless cars and delivery robots — among the “Top Five Technologies” that will define cities in the next decade.

Starship’s delivery robots work this way: Customers use a smartphone mobile application to order their delivery. A text alerts customers — “You have a robot waiting for you outside” — when the robot is near their home or business. A person must be present to receive the delivery because only the customer has a unique code to unlock the robot’s box.

Cities that have laid out the welcome mat for the robots see practical promise in what can first appear to be a passing fancy gizmo.

“We’re excited,” said Catherine Ralston, economic development manager of Redwood City. “They did a video in our downtown of the robot going into the bakery, picking up baked goods, and at the moment it rolled into City Hall, it popped open and presented the cookies to City Council.” They are thinking of using the robots for city services, such as delivering library books.

The Washington, D.C., City Council opened the door to the machines by passing legislation last month that allows up to five different robot companies to operate in the area, though not in the downtown business district.

“To be candid, I’m not at all futuristic. I’m a here-and-now kind of person,” said Leif Dormsjo, head of the District’s Department of Transportation. “But our approach to transportation innovation is that we want to be a catalyst for new and interesting technologies. We have a permissive attitude about cooperating with new technologies.”

Whether city dwellers will be as enthusiastic and accepting of the little robots as their city leaders are is an open question.

“Humans don’t always act in rational ways,” said Prof. Missy Cummings, director of the Humans and Autonomy Lab at Duke University. “Look, I’m from the Deep South, and as soon as a robot delivers a six-pack of beer down there, they’ll get out the guns and shoot it up.”

Starship Technologies already has robots operating in 58 cities in 16 countries around the world, Martinson said. More than 1.7 million people have encountered the robots on sidewalks, or used their services — without incident, he said.

“We took a video in London showing that 3,000 people passed by our robots without even noticing them.”

Ralston of Redwood City said test robots rolling around the city haven’t caused any issues so far. “People enjoy seeing the little robots. Or they completely ignore them, they don’t even take a glance,” she said. “They realize, OK, there’s something rolling along the sidewalk. It looks all right.”

In a northwest neighborhood of Washington recently, one Starship robot drew some attention as it scooted around pedestrians and bicyclists on a busy sidewalk.

Resident Timothy Sanders stopped his bike to watch it weave in and out of human traffic, avoiding pedestrians and bikers. “It’s amazing, it’s very futuristic,” he said. Reginald Isaac stopped to watch it too. “Technology be real fly,” he said, laughing.