Obviously, it would be quite dangerous to navigate roads without having collected environmental data prior to autonomous driving. This is why Google engineers travel the route a few times beforehand to collect thorough data. In a recent video displaying the car's performance at an intersection, the self-driving Prius stopped at a red light. Not a big deal. But when the light turned green, the car started a left turn until it sensed a jaywalker. The car yielded to the pedestrian harmlessly.
Before the technology of self-driving cars is released to the public, cars and continuous 3D-mapping will have to go through extensive series of thorough and aggressive testing. Although the testing may get sickening, Google engineers are having fun at the same time (see the embedded Youtube video). In the video, the autonomous Prius speeds through a parking lot while navigating a circuit of cones.
The overall benefit of implying a long-term basis of autonomous cars is that an online network could improve 3D world-mapping and merge user inputs from individual autonomous cars to create one large, detailed map. In this way, users help each other by contributing to this detailed driving map collaboratively. Autonomous cars driving close to each other would create a continuous flow of cars and therefore reduce traffic while composing a leeway for faster cars. Smarter vehicles will undoubtedly make transportation increasingly safe and efficient by reacting faster than humans and preventing more accidents.
So why self-driving cars from a company emphasizing on search-engines? Google's goal is not just to make search engines and cloud storage, it's also to make the world more environmentally stable. Now we won't go into Google-certified houses, treadmills, electricity, and things like that, but Google has the technology necessary to create such autonomous technology. The market of autonomous vehicles is still sprouting, and it has high hopes by its potential customers and will turn prosperous by the energy-saving attitude our world has today.