When you think about it, left turns across two lanes of traffic going in opposite directions are kind of crazy. Only an admixture of luck, skill, and a collective social agreement to, as a general rule, avoid crashing into each other keeps you alive. In fact, left turns increase the potential for an accident and also waste fuel. So traffic engineers have come up with a new street design, called “superstreets” that get rid of left turns from side streets onto major roads. And a new study says they are both faster, and safer.