If you live in the U.S. but don't live in San Francisco or a few other select testbeds, you'll be forgiven for not knowing that robot deliveries are on the rise. But in many towns around the world, including Milton Keynes in England, robots are already a common sight on city streets.

Starship Technologies, a technology and logistics company focused on last-mile delivery services utilizing robots, is celebrating 50,000 commercial deliveries this week in 100 cities around the world. The company sees a change in consumer behavior toward more frequent demand for smaller numbers of items as key to its continued expansion.

The customer behavior is called "top up" shopping, and it pairs well with delivery robots with limited payloads but quick response times. Need pretzels? A bottle of milk? Rather than wait until the next trip to the store, a robot can have the items to your door in a matter of minutes.

"Since the robots came to our neighborhood last year, they've become such a popular and common sight in the community," Gillian Bailey, a local resident in Milton Keynes who received the 50,000th delivery made by Starship in the town. "With my hectic schedule, it's really convenient to get my groceries delivered by the robot right to my front door while I'm busy with other things around the house. Our community feels really lucky to have this service available in our area, and I know many people who use it regularly throughout the week. I've already made over 100 orders since Starship first set up shop here and I'll be making many more!"

Top up shopping is crucial to customer adoption of the robot delivery concept. It's no coincidence Starship has robots roving corporate and college campuses, including George Mason University in Virginia. College students and office dwellers in need of a quick snack are a perfect customer base and an ideal testbed to prove the robot delivery concept.

"It has been exciting to see the increase in 'top up shopping' by residents in Milton Keynes where they buy groceries on multiple occasions throughout the week now that they have the option of autonomous delivery," says Lex Bayer, CEO of Starship Technologies.

The push to change shopping habits seems to be working in Milton Keynes. Since the introduction of robot delivery a year ago, houses served in the town grew by 450 percent. The most popular items ordered in the last year include milk, bread and chocolate.

Starship, which contracts with local businesses to offer delivery services, will add a second co-op store in Milton Keynes.