Walmart will use fully autonomous box trucks to make deliveries in Arkansas starting in 2021. The big-box retailer has been working with a startup called Gatik on a delivery pilot for 18 months. Next year, the two companies plan on taking their partnership to the next level by removing the safety driver from their autonomous box trucks.

Gatik, which is based in Palo Alto and Toronto, outfitted several multitemperature box trucks with sensors and software to enable autonomous driving. Since last year, those trucks have been operating on a two-mile route between a “dark store” (a store that stocks items for fulfillment but isn’t open to the public) and a nearby Neighborhood Market in Bentonville, Arkansas. Since then, the vehicles have racked up 70,000 miles in autonomous mode with a safety driver.

Next year, the companies intend to start incorporating fully autonomous trucks into those deliveries. And they plan on expanding to a second location in Louisiana, where trucks with safety drivers will begin delivering items from a “live” Walmart Supercenter to a designated pickup location where customers can retrieve their orders. Those routes, which will begin next year, will be longer than the Arkansas operation — 20-miles between New Orleans and Metairie, Louisiana.

“Our trials with Gatik are just two of many use cases we’re testing with autonomous vehicles, and we’re excited to continue learning how we might incorporate them in a delivery ecosystem,” said Tom Ward, Walmart’s senior VP of customer product.

Gatik describes its approach to self-driving hardware and software as “radically divergent.” In a Medium post, Gatik CEO and co-founder Gautam Narang described the process that gives the company the confidence to pull safety drivers out of its vehicles:

We decompose the massive monolithic DNNs into micro-models whose intended functionality is restricted to a very specific explainable task, and build rule-based fallback & validation systems around them. Given extensive knowledge of Gatik’s well-defined ODDs and hybrid architecture, we are able to hyper-optimize our models with exponentially less data, establish gate-keeping mechanisms to maintain explainability, and ensure continued safety of the system for unmanned operations.

Walmart is working with a variety of self-driving companies in its search for the best fit for the company’s massive retail and delivery operations. In addition to Gatik, the big-box company is working with Waymo, Cruise, Nuro, Udelv, Baidu, Ford, and Postmates.