Nuro, the self-driving startup founded by two ex-Google engineers, is expanding its pilot robot delivery service in Houston, Texas, to include Walmart customers. The company has been making grocery deliveries in Houston with its fleet of autonomous Toyota Prius vehicles since March. Now the company plans to roll out its custom-built R2 prototype vehicle to help supplement its delivery duties.

In the coming months, Houston residents who have opted into Nuro’s pilot service can get their groceries delivered from Walmart in either of the company’s two types of vehicles: a Toyota Prius equipped with self-driving hardware and software or the oversized lunchbox-looking R2. The service will expand to the general public late in 2020, the company says.

Nuro is one of the few companies to be operating fully driverless vehicles on public roads

Nuro is one of the few companies to be operating fully driverless vehicles — that is, vehicles without safety drivers behind the wheel — on public roads today. Its R2 vehicle is about half as wide as a compact sedan, shorter than most cars, and there’s no room inside for human passengers or drivers. It is also an updated version of Nuro’s original R1 prototype, but with around 50 percent more capacity (which translates into about 18 more grocery bags).

Earlier this year, Nuro said it planned to increase its test fleet of standard cars fitted with self-driving hardware and software to about 50, which it will operate on public roads in California, Arizona, and Texas with safety drivers behind the wheel. The data accumulated from these tests would then be fed into the company’s machine learning program that powers its driverless vehicles. A spokesperson confirmed that the company’s fleet now stands at about 75 vehicles, a majority of which are Priuses.

The R2 may not have room for a human driver, but the vehicles aren’t completely unmonitored. Nuro uses chase vehicles with human drivers and remote technology to monitor each driverless vehicle as it makes its deliveries.

It’s been a pretty good year for Nuro, which, in addition to expanding its delivery tests, also received a $1 billion investment from Japanese tech company SoftBank. It was a huge vote of confidence for one of the lesser-known startups working on self-driving technology. Formed in 2016 by a pair of ex-Google self-driving engineers, Nuro has set itself apart by focusing on food delivery rather than people moving.

Updated December 11th, 12:10pm ET: Added more details about the size and composure of Nuro’s fleet