That $@!# traffic!

New Mexico Business Journal, July-August, 1999

Is traffic congestion entirely the product of a growing population? Some myths and realities are explored

Last year, the National Association of Industrial and Office Properties (NAIOP) launched a national effort to understand and discuss growth management techniques aimed at sprawl. With the assistance of Tony Downes, senior fellow at the Brookings Institution, Washington, D.C., a task force has explored growth-related issues such as traffic congestion. Some of the findings published here for the first time are relevant to the growth management initiative in Bernalillo County, New Mexico's most populous region.

The remarkable expansion of the U.S. economy over the past eight years and the creation of millions of new jobs have fueled a growth spurt in many cities and suburbs. Federal, state and local policies on transportation, environment and taxes have also affected the patterns of growth. In some communities, however, an unwanted side effect of our current prosperity has been what many believe are unwise growth patterns - the phenomenon known as sprawl - both urban and suburban.

Sprawl is essentially unlimited low density residential and commercial development extending outward from urban areas into rural areas. This pattern of land use is viewed as wasteful of both land and natural resources and costly to serve with public facilities. For some people it may also be physically unattractive.

But for others the face of sprawl is not so bad. After all, sprawl in many respects is the product of American affluence, enabling people to have a low density residential environment that allows property owners to "borrow" and enjoy the open space that surrounds them. Sprawl also includes work places located within reasonable distances of affordable housing. As the saying goes: "You drive until you qualify (for a mortgage)." The relative ease of commuting and shopping make suburban sprawl attractive to many families.

Sprawl is the target of growth management. The term means many things to many people. For some, it means slow growth, for others it means no growth at all. But generally, the term encompasses a whole range of strategies and techniques to address what are perceived as the negative effects of rapid, unplanned growth such as traffic congestion, air pollution and the cost of providing public services.

Frustration with rising traffic congestion is cruising many residents to demand a slowdown in growth to prevent even more congestion. Certainly the average citizen stuck in a traffic jam often blames worsening congestion on the region's growth of population and urban development. After all, rising congestion appears to be caused by more vehicles on the streets, and population growth is an obvious cause of such increases. But is this analysis correct?

Traffic congestion has gotten worse because there are more cars, trucks, and other vehicles on each mile of American roads than in the past, especially during peak commuting hours. This conclusion seems obvious, but it deserves further exploration. From 1980 to 1995, the number of persons living in the U.S. rose by 15.5 percent. The number of households increased by 22.5 percent - larger than the percentage increase in population because average household size fell. The number of vehicles rose by 29.4 percent. The number of vehicle miles traveled (VMT) by those vehicles soared 890 billion or 58.3 percent. There were about 1.2 vehicles owned by households per household in 1980, compared to 1.8 in 1995 - a gain of 50 percent.

If the same number of people as existed in 1980 owned the number of vehicles per person that prevailed in 1995, and drove each vehicle the same miles per year as prevailed in 1995, that would account for almost two-thirds of the increase in vehicle miles traveled from 1980 to 1995. That is exactly what has happened.

A part of that increase has been generated solely by the increase in population that occurred from 1980 to 1995; it equals 237.6 billion miles, or 26.7 percent of the total gain. Thus, population growth alone has generated only about one-fourth of the gain in vehicle miles driven from 1980 to 1995. But those added people are in fact owning vehicles and driving them at 1995 rates; and that change of rates accounts for 9.9 percent of the total gain in vehicle miles traveled from 1980 to 1995.

So growth in population plus the new behavior of the added population accounts for about one-third of all added vehicle miles driven per year from 1980 to 1995. Growth alone has not been the major cause of increased vehicular movements on American roads - that cause is changed behavior by the same number of people that lived here in 1980.

Why do Americans own more vehicles per household and drive each one much farther, on the average, than they did in 1980? One reason is that more household members now work outside the home and therefore must commute to work daily. When two or more persons in a household work outside the home, it is often difficult for the household to live close to its members' jobs, since those jobs may be in very divergent locations. If so, at least some household members may have to travel a long way to and from work.