Walmart is launching another pilot project involving self-driving technology, the company announced Tuesday. Customers in the Phoenix suburb of Surprise, Arizona, will be able to order groceries for delivery from a nearby Walmart store.

Walmart is conducting the new pilot program along with self-driving delivery startup Udelv. In its own post, Udelv says that the pilot program will begin later this month.

We talked to Udelv CEO Daniel Laury last July. Laury told us that he's a serial entrepreneur with three previous companies under his belt. When he co-founded Udelv three years ago, he said, "pretty much every single company out there was focused on taxis; no one was doing delivery."

Today there are a number of other startups working on delivery services, but a lot of them are focused on building small robots with space for only one or two customers' worth of merchandise. By contrast, Udelv has built its service using full-sized trucks and vans, potentially allowing them to make deliveries to several customers in a single trip.

Udelv hopes to sign deals with a wide variety of retailers. Walmart is now Udelv's most prominent customer, but it's far from the first. Udelv has already done deliveries for the California grocer Draeger’s Market and for a Texas auto parts chain, XL Parts.

"Over the past 12 months, Udelv has made thousands of deliveries for dozens of clients," Udelv said in its Tuesday blog post.

Udelv unveiled its latest vehicle, dubbed the "Newton," at the CES show this week. The vehicle is built using Baidu's open source Apollo platform for autonomous vehicles—a valuable endorsement for the Chinese search engine company, which is seeking to make its self-driving software an industry standard.

In the long run, Laury hopes to improve the customer experience by making deliveries more of an on-demand service. Conventional grocery delivery services often ask customers to be home during a multi-hour window. By contrast, he argues, autonomous vehicles should be able to schedule deliveries on short notice and with a precise delivery time—letting customers quickly accept the goods and then move on with their day.

"Our goal is to be able to give you a super-precise time at which we will be there, say 6:17pm plus or minus a minute," Laury told me last July. It's not clear how close the Walmart program will come to this ideal.

The self-driving delivery business is getting crowded

In recent months, self-driving companies and retailers have been teaming up at an accelerating pace. Walmart already has at least two other partnerships. Last November, Walmart announced a deal to test Ford's self-driving technology for grocery deliveries in the Miami area. Walmart also has a deal with Alphabet's Waymo to encourage passengers to take Waymo's self-driving vehicles to Walmart.

Ford has a number of other partnerships with retailers. A couple of years ago it experimented with delivering pizzas for Dominoes. Last year, it announced a pilot program with Postmates.

Last week, GM's Cruise unit announced a partnership with Doordash to deliver food using Cruise's self-driving car fleet in the San Francisco area.

As far as we know, all of these services still have safety drivers behind the wheel to intervene in case the vehicles malfunction. One notable exception is Nuro, a startup founded by two veterans of Google's self-driving program. The company started delivering groceries for a Kroger-owned grocery store last month using the company's small, fully driverless vehicles—though initially the vehicles were followed by human monitors in another vehicle.