Every day, tens of millions of men and women commute between home and work, and much of that commuting is done by car. As the number of cars increases on the road, the longer people have to sit in traffic, and the less free time they have for things they enjoy. For commuters stuck in traffic, even opening the window to get a breath of fresh air is impossible because of the choking fumes from polluted air. Traffic has become one of the modern world’s worst nightmares.