Traffic plateau clouds planning

(St. Louis Post-Dispatch, February 18, 2008 by Elisa Crouch)

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.

The stagnation is spurring discussions about how to plan for road projects. And in Missouri, it has raised concerns about how to generate more road funds, because gasoline tax revenue doesn't rise much when traffic is stagnant.

"It's going to change how we look at building the transportation system," said Les Sterman, executive director of East-West Gateway, which determines how federal transportation money is spent in the region. "Clearly, the level of traffic volumes that we expect will determine how much additional capacity we plan for in the system."

For decades, highway planners have pointed to rising congestion as reason to proceed with expansion, with the expectation that traffic would only worsen. In fact, planners could hardly keep up, Sterman said. If the pattern continues, it's likely to have an impact on long-term plans — those 20 to 30 years in the future.

The study shouldn't put an end to projects already on the to-do list, such as building a new Mississippi River bridge downtown and extending the Page Avenue extension (Highway 364) to Wentzville.

"We're so far behind the curve on just meeting the needs that are here today," said Ed Hassinger, district engineer for the Missouri Department of Transportation. "I'm not sure it has an affect on the here and now."

The trend statewide in Missouri and Illinois, and across much of the U.S., mirrors what is going on the St. Louis area.

But there are exceptions, for instance in western St. Charles County, where subdivisions, shopping centers and office buildings have replaced cornfields. Consequently, traffic on Highway 40-61 at Interstate 70 shot up 20 percent between 2000 and 2005, according to the report. Growth in places like Dardenne Prairie is responsible. "It was a sleepy little town when we moved out here," said Mike Page, who moved to Dardenne Prairie in 2001. Traffic, he said, "is definitely increasing."

Other high-growth spots include Interstate 44 in the Kirkwood area, and various sections of Interstate 270.

Those traffic booms aren't representative of the region.

"We're certainly not New York or LA," said Lance Huntley, of East-West Gateway, who co-authored the study. "They do have continued congestion problems, but here, we don't."

The organization used data from Missouri and Illinois, whose transportation departments calculate the miles traveled in the region each year. The federal government requires these counts, on every mile of a state's highway and interstate system. The number of vehicles counted each mile are added up to calculate the number of vehicle miles traveled.

"It's fairly accurate," said Mary Beth Antone, planning supervisor for the Missouri Department of Transportation.

AGE, OWNERSHIP

Several demographic factors are driving the stagnation, the authors of the study found.

One is the aging population. The median age in the metro area rose to 37.5 years in 2006, from 35.3 years in 2000, according to the U.S. Census. During that time, the percentage of the population older than 60 rose to 17.1 percent, from 16.3 percent.

Drivers at retirement age tend to drive about half as much as they did in their 30s, statistics say. Those 65 and older drive an average of 8,200 miles a year, compared with the more than 16,300 miles driven by those half their age, according to East-West Gateway.

Household size and composition also makes a difference. The average St. Louis-area household fell to 2.51 people in 2000 from 2.60 in 1990, according to the census. Two-parent households with children put more miles on their vehicles — an average of 15,339 miles a year per — than one-parent households or couples without children. Couples without children average 12,775 miles a year per driver. Single parents drive an average of 13,848 miles a year.

Female participation in the work force is having an impact. Nationally, the percentage of women working has plateaued at about 60 percent, labor statistics say. Specific numbers for St. Louis weren't available.

"The average driving time is about 20 minutes to work, so participation in the labor force typically does result in greater miles traveled," said Mark Tranel, director of the public policy research center at the University of Missouri-St. Louis. "For the postwar period until the '80s, there were significant increases in that rate. Now that rate has leveled off."

Vehicle ownership also may be close to hitting a ceiling, said John Posey, co-author of the study.

In Madison County, about 5 percent of households had no vehicles in 2006. The percentage in St. Louis County was 6 percent, St. Charles County was 3.5 percent and the city of St. Louis — where alternative forms of transportation are more widely available — was 21 percent. Those numbers are down from previous years.

"We're reaching a point where it's looking like there aren't that many more households in the region that are going to add cars," Posey said. "There are some households that don't have cars for whatever reason, whether it's disability or age, or they can't afford one, or personal choice. We just think that at some point, the rate of increase in auto ownership is going to have to level off."

So far, gasoline prices appear to be having little, if any, impact on traffic growth, according to the analysis. As prices rise and fall, the number of miles people drive remains steady. Still, it's a factor East-West Gateway isn't ready to rule out.

"That's something we're going to continue to monitor," Posey said. "Maybe gas prices don't have much impact in the short term, but they do in the long term."