Another thing to improve traffic has nothing to do with the roads. One of the reasons we have traffic congestion is simple, slow human reaction time. A lot of cars have an option called adaptive cruise control or ACC, which uses radar or laser sensors to measure what appropriate distances to keep. It also has software to apply the brakes or the gas pedal to follow behind other cars on the highway and do so at closer distance more safely and alerts you when to take needed action allowing more cars to be on the highway per hour. Right now the technology is found in luxury cars or higher end vehicles. Automakers should work to make the technology cheaper so it can be added to nearly any car whose typical cost is less than 15-20 thousand dollars; since it may only be a 1,500 dollar option, whats that for a 18,000 dollar sedan. Most of the advanced technology found in luxury cars eventually finds it’s way into generic models in as little as a few years such as original cruise control, automatic windows, dashboard navigation systems. It’ll be worth it. Once 15-20 percent of cars on the road use ACC on the highways regularly, congestion will be nearly cut in half and fuel savings will significantly improve because we wont idle on the highway so much. Interstate Highways only account for 4 percent of all our roads, but account for 25 percent of traffic and miles driven. De-congesting our major highways will lead to big fuel savings and money savings, and the cost would be transferred to the drivers (the ones responsible for making the roads congested) rather than the huge public costs associated with building additional roads.