The last we had heard of Google's self-driving car project was in August 2012, when Google announced that the cars had driven 300,000 autonomous miles. Today, that number has more than doubled to 700,000, and Google's cars are now tackling driving in the big city.

Google's cars could probably perform well in an ideal driving environment, but the real world is full of one-off situations that a self-driving car will need to be able to navigate. By trying to figure out city navigation, Google's cars more frequently run into these strange traffic situations.

Getting self-driving cars on the road requires teaching them to deal with a myriad of abnormal traffic conditions, and Google says it has built software models for "thousands" of different situations. The company has taught its cars to detect construction zones by recognizing yellow signs and traffic cones, and the cars can even change lanes as indicated by the cone layout. The cars now move to keep a safe distance from obstacles, like vehicles stopped on the side of the road. They won't stop in the middle of a railroad crossing, but instead will wait on one side of it until there is enough room in the traffic ahead for the car to fully cross.

Often, the worst part of driving is other drivers and pedestrians, but Google says, "What looks chaotic and random on a city street to the human eye is actually fairly predictable to a computer." The cars now model things like the likeliness of a car running a red light, and they can detect cyclists, read their hand signals, and predict their movement. Google's cars have also learned to not run down pedestrians and cyclists at crosswalks, and they can even track objects behind them.

The company admits that it still has a lot of work to do, and it's sticking to its hometown of Mountain View for now. Google notes that over 30,000 people die in traffic accidents in the US every year. A self-driving car will never get tired, distracted, or drunk, and it can see farther than its human counterparts, see at night, and see in 360 degrees. This is one of the rare projects that could change the world, and Google says it's "optimistic" that a self-driving car is an achievable goal.