Because of these factors, a table that estimates CO2 emissions based only on a single variable, such as trip distance, cannot provide an accurate estimate. These factors include individual driving behavior, vehicle and roadway types, and traffic conditions. This question is difficult to answer, because CO2 emissions, and the fuel consumption that causes them, are very sensitive to several factors. The key question is how big of an emissions reduction we can get by reducing congestion. Therefore, congestion mitigation programs should reduce CO2 emissions. As traffic congestion increases, so too do fuel consumption and CO2 emissions. Policy makers have placed less attention on reducing CO2 emissions by reducing traffic congestion. Alternative fuel possibilities include many low-carbon options such as biofuels and synthetic fuels. Those who promote vehicle improvements have focused on building lighter and smaller vehicles (while maintaining safety), improving powertrain efficiency, and introducing alternative technologies such as hybrid and fuel cell vehicles.

To reduce CO2 emissions from the transportation sector, policy makers are primarily pushing for more efficient vehicles, alternative fuels, and reducing vehicle miles traveled (VMT). Roughly a third of America’s carbon dioxide (CO2) emissions come from moving people or goods, and 80 percent of these emissions are from cars and trucks.

Surface transportation in the United States is a large source of greenhouse gas emissions, and therefore a large contributor to global climate change. Congestion does more than waste time, it adds to localized pollutants.

Huge traffic jam