Amazon's autonomous robots have started delivering packages in Southern California

For much of this year, a fleet of Amazon Scouts, mini tank-like delivery vehicles about the size of a cooler, have traversed residential neighborhoods in a Seattle suburb to deliver packages.

During that period, the autonomous vehicles, which roll along at walking speed, have endured the full spectrum of the Pacific Northwest's weather, including one of the largest snowstorms of the past decade.

Now, after nearly eight months of street tests and thousands of successful deliveries, Amazon has announced that Scout has begun delivering packages to customers in Irvine, California. (Amazon CEO Jeff Bezos owns The Washington Post.)

The company said the light blue and black robots are able to safely navigate typical neighborhood obstructions such as trashcans, skateboards and lawn chairs. And yet the six-wheeled, battery-powered machines can't climb steps and will initially be chaperoned by a human employee to monitor their progress.

A self-driving delivery robot that Amazon is calling Scout. Photo / AP

"To kick-start our journey, we created dedicated hardware and software labs in Seattle," Amazon said in a statement online. "These labs give engineers, scientists, and our operations staff the opportunity to quickly build and test the delivery devices. We don't need to wait on external parts or software updates; we can rapidly prototype hardware components and write new code, and are able to validate our efforts in real-time."

Amazon is just one contestant in the race to perfect autonomous, last mile delivery vehicles capable to transporting food and packages from warehouses to doorsteps as quickly and cheaply as possible. In recent years, various companies have tested robotic delivery vehicles in California; the District of Columbia; Miami; Michigan and Las Vegas. The testing locations range from bustling neighborhoods to quiet office parks with limited foot traffic.

On college campuses around the country, food deliveries via robot are increasingly common. After a fleet of 25 delivery robots from the Bay Area start-up Starship Technologies descended on Virginia's George Mason University's campus in January, campus officials recorded a spike in breakfast orders.

In Ann Arbor, Michigan, the creators of a new autonomous vehicle have designed their robot to operate on local streets - but more like a bicycle than a car. Built by a startup called "Refraction AI," the REV-1 - a four-foot tall robot that weighs about 80 pounds and travels at a top speed of 15 mph - can operate in both car and bike lanes.

For now, Amazon said, the company plans to roll out a "small number" of Scout devices, which will operate Monday through Friday, during daylight hours. Local Amazon customers may receive their package from a scout or one of the company's typical delivery partners.

Despite being accompanied by human guides, it's safe to assume Amazon Scouts already have a detailed lay of the land. In June, the Verge reported that Amazon engineers have begun creating "detailed virtual maps of American suburbia" for the company's robots to absorb. Scout vice president Sean Scott told the publication that the three-dimensional models - which include details like sidewalks and storm drains - are used to train the machines for the real world.

"We can run thousands of deliveries in simulation overnight versus taking a bot outside in the real world," Scott told the Verge. "The bot doesn't actually know it's in a simulation. It thinks it's in the real world, which is pretty cool."

Scott said that once a Scout vehicle arrives in your neighborhood, its non-threatening look, down to its rubber wheels and curved exterior, are designed to help the robot blend in to its surroundings. If Amazon is lucky, he said, you might not notice the machine at all.

"We want the robot to fade into the background," he said. "We call it 'design for boring.' "