Demographic Trends Affecting Transportation (continued)
Commuting Patterns Shift to Suburbs
According to Commuting in America III, published by TRB in October 2006, since 1980 the percentage of commuters driving alone has increased from 64 to 76 percent; the percentage carpooling has decreased from 20 to 12 percent; transit riders have declined in percentage from 6 to 5 percent; those walking declined from 6 to 3 percent; and those who work at home have increased from 2 to 3 percent. Transit use is more prevalent in densely populated areas such as downtowns and along well-served transit corridors in the 12 mega-metropolitan areas such as New York, Boston, and Chicago.
From 1990 to 2000, 64 percent of the growth in metropolitan commuting was in flows from suburb to suburb, now representing 46 percent of commuting trips. The next largest growth area was the “reverse commute” from central city to suburb, now representing 9 percent. The “traditional commute” from suburb to central city dropped in share to 19 percent.
Figure 13. Projected Vehicle Miles of Travel, 2004–2055
Figure 14. Growth in Trade as a Percentage of U.S. Gross Domestic Product
Freight Trends Present Major Challenges
Freight movement will be one of the major challenges for the years ahead.
The real change of note is what is taking place with regard to the degree to which our economy is dependent on foreign trade. Trade as a percentage of GDP increased from 13 percent in 1990 to 26 percent in 2000, and is expected to reach 35 percent by 2020. We are indeed moving into a global economy. (Figure 14.)
Trucking tonnage is projected to more than double between 2004 and 2035, to 24 billion tons, a 114 percent increase. Rail tonnage is projected to grow by 63 percent to over 4 billion tons. (Figure 15.) By 2035, it is anticipated that trucks will carry 79 percent of total tonnage. The share of tons carried by truck will slightly increase by 2035, while the modal share carried by rail is expected to decline from 14 to 13 percent.
The increase in freight demand and truck travel means that where today we have an average of 10,500 trucks per day per mile on the Interstate highways system, tomorrow there will be an average of 22,700 trucks per day per mile, with the most heavily used portions of the system seeing upwards of 50,000 trucks per day per mile. Only 30 miles on the Interstate carry more than 50,000 trucks today; by 2035 that number will reach 2,500 miles. To accommodate this growth there will have to be significant increases in capacity. What these volumes of truck traffic may require are dedicated truck lanes.
Figure 15. Projected Freight Ton Growth by Mode, 2004–2035
Much of the congestion on the Interstate System is occurring at bottlenecks—specific locations that routinely experience traffic backups because traffic volumes exceed highway capacity. These bottlenecks, including interchanges, steep-grades, signalized intersections, and lane drops, accounted for the most truck-hours of delay, estimated at about 124 million hours annually in 2004. State programs that target relieving these bottlenecks may be needed.
As NAFTA trade with Canada and Mexico has increased, so too has truck traffic. Since 1994 when NAFTA went into effect, there are 30,000 additional truck crossings per day in the four Southwestern states of Arizona, California, New Mexico, and Texas. In 2004, there were 11.4 million trucks that crossed the Canadian and Mexican border into the United States.
Over the next 20 years, while truck freight is expected to double, international containers are expected to quadruple. (Figure 16.) A great deal of this increase in container volume is coming from Asia, and especially China. These volumes are growing rapidly especially on the West Coast. (Figure 17.)
Figure 16. Historic and Projected U.S. Container Traffic (TEUs)
Ports on both coasts are expecting growth, but by 2010 trade is expected to outstrip port capacity in every region of the country. (Figure 17.) Meanwhile, truck volumes are increasing rapidly as well. Peak-hour congestion on the Interstate System in metropolitan areas is expected to increase from 29 percent in 2000 to 46 percent by 2020. And this comes at a time when U.S. retailers and manufacturers are almost totally dependent on “just-in-time” delivery. Store shelves and manufacturing assembly lines have to be resupplied, sometimes within a 15-minute window. Reliability is a must. So the entire freight system of shippers, carriers, highways, railroads, ports, retailers, manufacturers, and customers face some major challenges.
Figure 17. Port and Terminal—Forecast Capacity/Demand (Millions of Twenty-Foot Equivalent Container Units)
