The prospect of riding around in driverless cars is exciting, because they have the potential to be much safer than current modes of transportation. Human drivers, even the best ones, are fallible. Distractions roll in and it becomes increasingly difficult to be aware of all of the car's surroundings at once. Driverless vehicles don't have that problem.
These vehicles are constantly sending out light and radar signals and receiving them as they bounce back off of buildings, vehicles, and other objects in the environment. The computer then translates this stream of signals into a real-time 3-D rendering of the street. It has a more thorough understanding of traffic thank a human driver could ever dream of having.
One crucial thing to remember when watching the video is that although it is impressive and beautiful, it isn't perfect. The detail is impressive, but there are still gaps that could potentially put the passenger, pedestrians, or other drivers at risk. This may be a problem now, but will not be for long as the technology continues to develop.
The future looks amazing, which is exactly what this video shows: