USC graduate student Jeremy Fuller put it eloquently when he said, "Traffic really just defines your possibilities at any given time." When traveling from one side of a large metro area to another in the US, a single individual has very little control over her travel time. You can try to pick a less congested time of day or select from a few alternate routes but if the city is gridlocked you are out of luck.

According to the most recent Annual Urban Mobility Report, annual hours wasted in traffic in the largest metro areas of the US increased by 33 hours per year between 1982 and 2012 (from 19 to 52). That means every year Americans in the largest cities are wasting one more hour of their life in traffic. There are 15 of these areas with over 3 million residents each, so even small differences in time wasted add up. The worst offender is the DC area at 67 wasted hours per driver per year.

The Los Angeles area is notorious for its traffic, but the situation is improving. Although the 2011 figure of 61 hours per driver-year is still high, it is down from 78 hours in 2005.  Part of the improvement comes from synchronizing the city's 4,500 traffic signals over the 469 square-mile metro area:

The system uses magnetic sensors in the road that measure the flow of traffic, hundreds of cameras and a centralized computer system that makes constant adjustments to keep cars moving as smoothly as possible. The city’s Transportation Department says the average speed of traffic across the city is 16 percent faster under the system, with delays at major intersections down 12 percent.

Without synchronization, it takes an average of 20 minutes to drive five miles on Los Angeles streets; with synchronization, it has fallen to 17.2 minutes, the city says. And the average speed on the city’s streets is now 17.3 miles per hour, up from 15 m.p.h. without synchronized lights.

The natural question to ask is, "but then what?" There could be second-order effects: as traffic time is reduced, more commuters could switch to driving. And as the city continues to grow there will be more cars on the road. For now, though, this represents a major improvement that cuts down on one of the main hidden costs in urban life.

Read more about how other major cities are fighting traffic problems here. You may also be interested in traffic signals as a metaphor for property rights or the safety of traffic circles.