The New York Times has an article today suggesting that bringing back the 55 mph rule on highways is a good way to reduce America’s energy consumption. If you look at the story’s own graphic, however, it’s not at all clear that the limit had any effect on consumption between 1973 and 1987 (when it was imposed and when it was relaxed). The idea also brought to mind a conversation I recently had with one of my brothers. He’s got one of these newer model cars that has a real-time display reporting how many miles to the gallon the car is getting. So I asked him if there was an optimal speed in terms of fuel use. “Yeah,” he said. “Zero.”