Traffic in the St. Louis area has plateaued this decade, ending years of fast growth that fueled demand for more and wider roads.

A recent analysis by East-West Gateway Council of Governments shows traffic growth in the eight-county region slowed to an average annual rate of less than 1 percent between 2000 and 2006.

That's down from 2.3 percent average growth in the 1990s, and 4.3 percent growth in the 1980s.

The reasons behind the phenomenon have to do with the area's demographics: The region's population is aging, households are getting smaller and the percentage of women in the work force has stabilized. The price of gasoline had little, if any, effect on traffic, the analysis shows.