In periods of high traffic, one person can have a great influence on cars behind him or her. Livescience.com describes how reaction times, lapses in attention, and erratic driving (faster or slower than other traffic or the switching of lanes) can cause ‘traffic jams.’
Behavioral economists explain that in most places roads are free, so there is little incentive for drivers not to over-utilize them. Economic incentives or road pricing are measures that can prevent recurring congestion. Evidence based on the induced demand hypothesis suggests that building more freeways increases traffic congestion. With extra road capacity, more cars will use the road and as a result more traffic congestion will arise. It has also been likened to an obese person loosening their belt as a cure for obesity.
Some economists have argued for congestion pricing, which is charging higher tolls for driving on roads when there is more congestion. This idea is thought to change the incentives, so that people will find alternatives to driving in the most congested times (e.g., taking public transportation, leaving at different times, car pooling, etc.). Daniel Gross has an article in the NY Times describing his ideas.