Mercedes drove around the globe to train its autonomous cars

On a rainy September day in Frankfurt Germany, Mercedes-Benz executives and I got in a specially built semi-automated S-Class to track our drive to Stuttgart. It was the first leg in a five-month, five continent training of the automaker's self-driving system called the Intelligent World Drive that ended at CES earlier this month. It's easy to forget that road laws and regulations differ not only in other countries but even within the United States. While Californians are used to right-turns on red lights and motorcycles lane splitting on the highway, in other places, both of those are not only frowned upon, they're illegal. That means automakers not only have to learn the local laws of each region but the driving habits of the people in those areas plus varying signage and road markings.