I put together a post about four and a half years ago called What might a future grocery store look like?. It discussed how robots were starting to appear in warehouses - as of January this year Amazon was operating 45000 of them - as well as what a delivery bot of the future might look like. Amongst what I was thinking back then back then:
a substantially lighter vehicle - don't forgot also the weight of a human driver. ... should it be bigger? smaller? (I'm guessing a limited-speed, light-weight vehicle would be easier to get government approval of than running full-size vehicles). You could eliminate most of the parking lot for most grocery stores and, as the vehicles would be operating within a short range of home base electric vehicles might be more feasible.
Now it seems like these delivery bots are getting to the point where you might start to see these things in operation soon. e.g. Postmates and DoorDash are testing delivery by robot with Starship Technologies (the article has an image of these in front of the White House):
Starship’s robots look something like a cooler on wheels. They travel at a top speed of about 4 miles per hour on busy town sidewalks or streets where the company has attained regulatory permission to roll among the people, and make deliveries. They can carry just over 40 lbs. at a time, and are generally programmed to deliver within a two-mile radius in real world scenarios.
Starship’s nearly self-driving robots are also powered by rechargeable lithium-ion batteries, so they’re relatively quiet and clean compared to something like diesel trucks idling on your corner, or the hoopty a driver may use for their pizza delivery job. A human operator oversees the use of the robots remotely through a fleet management app, but they primarily rely on computer vision and street map data to navigate and drop off an item at a customer’s door.
Small. Slow speed so low risk of inflicting serious damage. A relatively short delivery radius. Battery powered. Another article on the same robots:
Starship Technologies’ robots have already driven thousands of miles in cities around the world, and the company even helped get legislation put in place to make the testing possible in Washington, DC. While these will be the company’s first two commercial trials in the US, Starship has already performed deliveries in the UK and Germany thanks to partnerships with services like Just Eat, Pronto, and Hermes.
The second article discusses airborne drone deliveries but for the moment those seem a bit gimmicky to me. I also expect to see more vehicle like the ones below, but those are larger-sized units. I find the little ones more interesting.