Waymo is perhaps the leader in the race to develop a safe and robust self-driving system, and it's just strengthened its relationship with Fiat Chrysler Automobiles.

The two companies announced Wednesday plans to start testing a Level 4 version of Waymo's Waymo Driver self-driving system in FCA's light commercial vehicles, specifically the Ram ProMaster van.

Level 4 on the SAE scale for self-driving capability means a vehicle that can handle its self for extended periods, though only within set conditions. FCA has been building Chrysler Pacifica minivans equipped with the L4 Waymo Driver since 2016 for use in Waymo's various trials. Some of those trials have been without a backup human driver behind the wheel.

The Ram ProMaster vans equipped with the L4 Waymo Driver will be used to transport goods in a trial whose aim is to address specific needs of commercial customers, particularly those in the delivery business.

Waymo and FCA also announced Wednesday that the Waymo Driver will eventually be fitted across the FCA portfolio of vehicles, including for personal use. The two companies are already working on future FCA vehicles equipped with self-driving systems. Waymo and Volvo also announced in June plans to establish a self-driving taxi service, while Waymo and the Renault Mitsubishi Nissan Alliance in 2019 said they would explore the potential for a self-driving taxi service.

“FCA was our first OEM partner, and we’ve come a long way together,” Waymo CEO John Krafcik said in a statement. “Together, we’ll introduce the Waymo Driver throughout the FCA brand portfolio, opening up new frontiers for ride-hailing, commercial delivery, and personal-use vehicles around the world.”

FCA's merger with PSA Group to create the new auto giant Stellantis also paves the way for the Waymo Driver to be fitted to vehicles from brands currently controlled by PSA Group, leading to the potential for Waymo's trials to be expanded outside North America. Krafcik said in 2018 that Waymo was looking at entering Europe.

"We are not discussing details of the merger at this time,” FCA spokesman Nick Cappa told Motor Authority in an email. “However, our agreement allows for the benefits and obligations of our expanded partnership with Waymo to apply to both FCA’s current and future affiliates."