The two-seater vehicles, which have no pedals or steering wheels, travelled millions of miles in road tests.

Waymo is now concentrating on integrating its technology into other vehicles rather than building its own.

In a blog post, the firm said it was working on a fleet of 600 Chrysler Pacifica minivans.

Unlike the Firefly, which could only travel at 25mph, the minivans can drive at full speed.

"From the beginning, Firefly was intended as a platform to experiment and learn, not for mass production," wrote lead industrial designer YooJung Ahn and lead systems engineer Jaime Waydo.

"By designing and building a truly self-driving vehicle from scratch, we were able to crack some of the earliest self-driving puzzles?—?where to place the sensors, how to integrate the computer, what controls passengers need in a car that drives itself."

The pair added that using an existing car would enable the firm to bring self-driving technology "to more people, more quickly".

Fireflies will be displayed in Austin and Mountain View in the US and at the Design Museum in London.