It's a warm day in Mountain View, and just outside the Computer History Museum, Lexus SUVs are pulling up to the curb. The Lexus RX450h is a beautiful car, but today my eye travels immediately to its roof, where an attached laser radar array is spinning at 10 times per second. At around $70,000, the laser array is more valuable than the vehicle itself. A pair of test drivers invites me to climb in the back. I'm about to take a ride in Google's self-driving car.

After years of working mostly in secret, Google is beginning to speak more publicly about what its autonomous vehicle can do. There's a reason the company has decided to explain its program more fully: its cars are moving from the highways, where they typically interact only with other cars, to cities, where they are contending with pedestrians, cyclists, moving vans, and freight trains, among hundreds of other objects. As autonomous vehicles start becoming a part of daily life — at least for residents of the Bay Area — Google will face new questions, concerns, and regulatory hurdles.

And so roughly two dozen members of the press have assembled not far from Google's headquarters at the museum, to meet with the leaders of the self-driving car project and speak with a panel of experts on transportation, auto safety, and urban issues. The real lure, though, is to take a ride in one of these vehicles, and just after noon my number is called.

It's time.