Google's self-driving car

A prototype of Google's own self-driving vehicle is seen during a media preview of Google's current autonomous vehicles in Mountain View, California September 29, 2015. REUTERS/Elijah Nouvelage

A Google employee on a bicycle acts as a real-life obstacle for a Google self-driving prototype car to react to during a media preview. REUTERS/Elijah Nouvelage

Dmitri Dolgov, Principal Engineer on the software team of Google's Self-Driving Car project, speaks to the media. REUTERS/Elijah Nouvelage

Google co-founder Sergey Brin gets in a self-driving Lexus prototype following a presentation at a media preview. REUTERS/Elijah Nouvelage

Google co-founder Sergey Brin takes questions from the media following presentations at a media preview. REUTERS/Elijah Nouvelage

A line of Lexus SUVs equipped with Google self-driving sensors await test riders during a media preview. REUTERS/Elijah Nouvelage

Google vehicle operator Reko Ong stands next to a prototype of Google's own self-driving vehicle during a media preview. REUTERS/Elijah Nouvelage

The rear of a Lexus SUV equipped with Google self-driving sensors is seen during a media preview. REUTERS/Elijah Nouvelage

A prototype of Google's own self-driving vehicle is seen during a media preview. REUTERS/Elijah Nouvelage

Google co-founder Sergey Brin takes questions from the media following presentations at a media preview. REUTERS/Elijah Nouvelage

Jouralists take a test drive in a prototype of Google's own self-driving vehicle during a media preview. REUTERS/Elijah Nouvelage

Journalists take a test drive in a self-driving Lexus SUV during a media preview. REUTERS/Elijah Nouvelage

A prototype of Google's own self-driving vehicle is seen during a media preview. REUTERS/Elijah Nouvelage

Chris Urmson, Director of the Self Driving Cars Project at Google, poses for photos in front of a prototype self-driving car during a media preview. REUTERS/Elijah Nouvelage