Roads are the backbone of our society and economy, taking people and goods across distances long and short. They are a staple of the built environment, taking up nearly 2.8 million lane-miles (or 4.6 million lane-kilometers) of the United States’ surface area.
These same roads have a considerable life-cycle environmental impact, having been associated with over 75 megatons of greenhouse gases (GHG) each year over the past three decades in the United States. That is equivalent to the emissions of a gasoline-powered passenger vehicle traveling over 190 billion miles, or circling the Earth more than 7.5 million times, each year.