Fiat Chrysler announced that Waymo will add 500 Chrysler Pacifica Hybrid minivans to its self-driving program.

The automaker previously delivered 100 minivans, modified for self-driving, to Waymo during the second half of 2016.

Production of the additional 500 minivans will ramp up beginning in May, according to Fiat Chrysler. Waymo then will outfit the vehicles with its self-driving technology.

“The collaboration between FCA and Waymo has been advantageous for both companies as we continue to work together to fully understand the steps needed to bring self-driving vehicles to market,” said Sergio Marchionne, CEO of Fiat Chrysler. “The addition of 500 Chrysler Pacifica Hybrid minivans is a further acknowledgement of the hard work put forth by both engineering teams.”

The Chrysler Pacifica Hybrid minivans are equipped with Waymo’s hardware suite and self-driving software, which has been honed with nearly 3 million miles of on-road testing and billions of miles in simulation. The minivan’s electrical, powertrain, chassis and structural systems were modified to accommodate Waymo’s self-driving technology.

Waymo and Fiat Chrysler co-located a select group of engineers at a facility in southeastern Michigan to accelerate the overall development process. In addition, they conducted extensive testing at Fiat Chrysler’s Chelsea Proving Grounds in Chelsea, Mich., and Arizona Proving Grounds in Yucca, Ariz, as well as Waymo test sites in California.

Waymo Invites Public to Try Self-Driving Minivans

Waymo, formerly the Google self-driving car project, also announced that it is inviting members of the public to use its fleet of self-driving vehicles for everyday travel. Waymo’s early rider program will give selected Phoenix residents the opportunity to experience the self-driving Chrysler Pacifica Hybrid minivans for the first time.