Google’s self-driving car project is probably one of the most audacious experiments the company has embarked upon. Today, Google announced another milestone for this project: its fleet of about a dozen autonomous cars has now driven 300,000 miles without a single accident under computer control. While this is obviously very positive news for the project, Google warns that “there’s still a long road ahead.” The cars still need to learn how to handle snow-covered roads, for example, and how to interpret temporary construction signs and other situations that could throw its systems for a loop.