Science has firmly established that climate change is a public health issue and that human activity is causing climate change. International and domestic policy negotiations are under way to decrease greenhouse gas (GHG) emissions, in particular CO2, a major contributor to climate change. The transportation sector accounts for 33% of U.S. GHG emissions, second only to utilities such as power plants. Improving our transportation system will not only decrease GHG emissions, but also improve the public’s health.