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Publication Number:      Date:  Sept/Oct 2000
Issue No: Vol. 64 No. 2
Date: Sept/Oct 2000


Transportation in The 21st Century

by Robert E. Skinner Jr.

The following article was adapted from a paper presented by Bob Skinner, executive director of the Transportation Research Board, at the Johns Hopkins Applied Physics Laboratory on June 9, 2000. This paper was also the basis for remarks by Skinner to the American Association of State Highway and Transportation Officials (AASHTO) Research Advisory Committee Meeting on July 31, 2000.

Amtrak Acela
Amtrak says that its new Acela (the name represents a combination of increased acceleration and excellence in service), currently offering daily service between Boston and Washington, D.C., shaves 90 minutes off the travel time between Boston and New York City.
[credit Federal Railroad Administration]

Speculating about how transportation in the United States may evolve in the first few decades of this new century is clearly ambitious, and given the scale of our transportation system, it can be approached only partially. It is risky because everyone is a transportation expert -- that is, most of us are not only customers but also operators of the system. And it is a bit presumptuous because talking about the future of transportation inevitably takes one well beyond transportation; it is intertwined with our lifestyles, our economic well-being, and our environment.

I am going to take on this challenge. My comments are not intended to reflect my own personal preferences; rather they are intended to describe a transport future that seems probable based on what we now know.

I will begin by presenting a broad view of transportation and change. Then, I will discuss some important trends and characteristics of transportation that will influence its evolution in the United States, and I will conclude with some brief comments on specific proposals that have been advanced for transportation.

A Broad View

Let me offer three propositions about transportation as a driver of change and as a reactor to change.

First, with due respect to the computer and other technologies, the 20th century was the century of transportation technology. Aircraft and the mass production of motor vehicles changed the way we live, work, recreate, and even fight wars. The changes in mobility that they introduced were so great and so broadly accessible in the United States that they were key drivers of change throughout society.

Second, in the 21st century -- at least for the first few decades -- no breakthrough transportation technologies of that sort are on the horizon. In a world of financial and environmental constraints, we are more concerned with the preservation of the level of mobility that Americans already enjoy than with expectations of quantum leaps in mobility.

Third, information technology (including telecommunications) and biotechnology are more likely breakthrough technologies of the 21st century, continuing trends that are already evident. Of these, information technology promises to have the most immediate effect on transportation.

Information technology can be a substitute for transportation (e.g., video conferencing), but perhaps more importantly, it reduces the need for critical mass -- that is, for concentrations of employment -- especially as the United States increasingly becomes a service economy. It is the great equalizer that allows an individual to have the same access to information whether he is at home or in the office and that allows companies to operate as well in Des Moines as in New York. It is a powerful force for dispersal -- just as the industrial revolution was for concentration.

And the introduction of new information technology is happening quickly:

Now let me turn to four other areas that will exert strong influence on the evolution of transportation: demographics, institutions, capacity of the existing system, and -- what I see as a bit of a wild card -- human adaptability.


As Alan Pisarski, the author of Commuting in America, often says, "Demographics are destiny." What are our demographics and how are they changing? What will be our demographics 20 or 30 years from now?


Certainly, there will be more of us -- 20 percent more by 2020 and 43 percent more by 2050 according to mid- range Census Bureau forecasts. But our rate of growth is slowing from an annual rate of 1.9 percent in the late 1940s to 0.9 percent in 1996.3

We are becoming a nation of immigrants again. The immigrant population nearly doubled between 1950 and 1990. 3 A net population growth from immigration of 820,000 per year is assumed in Census Bureau projections through 2035. 4


More of us will be older. Now, 13 percent of the U.S. population is more than 65; by 2025, the projection is 19 percent.4 And gerontologists tell us that older Americans of the future will not want to live as older Americans have in the past.


Women are closing the gender gap. In 1970, 43 percent of women participated in the labor force, but by 1998, 60 percent of women were at work. As a benchmark, it is useful to compare the percentage of working women with the percentage of working men and to express that comparison as a ratio. The ratio of working women to working men went from 0.54-to-1 in 1970 to 0.8-to-1 in 1998. 4

From 1975 to 1995, the percentage of women with a driver's license grew from 68 percent to 85 percent -- a 17-percent increase. During the same period, the increase for men was only 4 percent -- from 88 percent to 92 percent. In 1995, the ratio of the percentage of women with a driver's license to the percentage of men with a driver's license was 0.92-to-1. 3

It seems likely that the remaining small gaps in labor force participation and driver's license rates will be effectively closed. As a result, schedules become very complex. Travel is increasingly organized into "chains" of trips (work, shopping, child-related), and such trips are difficult to serve with public transportation.

Suburban area
In many suburban areas, the vast construction of shopping malls and office buildings is turning suburbs into "edge cities" where people go to shop and work. In the 20 years from 1970 to 1990, suburb-to-suburb commuting rose from 15 percent to 44 percent of work trips. The diffusion of jobs to the suburbs makes it more difficult to serve commuters with conventional transit.
[Photo credit Zac Ellis]

We hope to be more affluent, and that expectation is reasonable based on our recent experience and our prospects.

Measured in "chained 1992 dollars," the disposable personal per capita income in 1998 was 1.33 times the 1980 figure and 2.3 times the amount in 1960. 4

More people are traveling more often. Between 1970 and 1990, while the population increased by 29 percent, the passenger-miles traveled increased by 95.3 percent. 5 For trips more than 100 miles (160 kilometers), leisure is the big gainer; the work trip is no longer the dominant determinant of travel demand.


We have become a nation of suburbs, and a big question is whether or not this trend will continue.

In 1940, 15 percent of the population of the United States lived in suburbs; 32 percent in center cities; and 52 percent in rural areas. By 1990, the suburban and rural percentages nearly flip-flopped with 47 percent in suburbs, 32 percent in center cities, and 21 percent in rural areas. 3

Suburb-to-suburb commuting in metropolitan areas accounted for about 15 percent of work trips in 1970 and for 44 percent in 1990. 6 The implication of this is that it is getting harder to serve work trips with conventional transit.

But ironically, rural areas are now growing as fast as metropolitan regions. 3 A recent Census Bureau study reported that, in 1995, more Americans relocated to rural areas than to metropolitan areas. 7 Rural Americans of the future will not be like the farmers of the past. Most will have the same values and the same desires for amenities and activities as suburban dwellers.

Use of Motor Vehicles

If current trends persist, we will probably be "saturated" with motor vehicles. Indeed, it looks like we already are.

Households without automobiles declined from 20 percent to 8 percent between 1969 and 1995. At the same time, households with two or more motor vehicles increased from 30 percent to 60 percent. 3 All this happened while the average household declined from 3.14 to 2.65 persons between 1970 and 1995. 4

Persons per vehicle declined from 2.6 in 1955 to 1.3 in 1995.

In 1990, 91.4 percent of workers traveled to work by automobile, and only 5.5 percent used transit. 4 (These statistics probably exclude people who work at home.) In 1995, 81.3 percent of all intercity trips of greater than 100 miles (160 kilometers) were made by automobile, and 16.1 percent were by air. 4

In 1993, trucks carried 72 percent of freight shipments by value and 24 percent of ton-miles. By comparison, the figures for rail were 4 percent and 26 percent, respectively, and for water, the numbers were 4 percent and 24 percent, respectively. 5

Transit's share of work trips is still falling 6.4 percent in 1980 and 5.3 percent in 1990.6 [Note: These figures are calculated from Pisarski's Commuting in America II to exclude people working at home.] Given the trends noted previously, this trend is likely to continue even though many transit organizations have recently reported increases in riders in absolute terms.

In summary, the United States has a growing population that is older, more affluent, and places a greater emphasis on leisure travel. It's highly suburbanized and heavily reliant on motor vehicles for passenger travel and freight. The tendency for dispersal continues -- even a return to rural areas.

Transport Institutions

How our nation organizes, regulates, and finances transportation systems plays a big role in determining the availability, cost, and quality of service. The transportation industry is, in fact, not one industry but rather a collection of industries. Transportation is a public and private enterprise that is highly decentralized.

How is our organization of transportation changing and how will it look in the future?

Private Sector

The private sector has undergone a significant transition over the past 20 years. There has been significant consolidation of railroads, airlines, and trucking firms; it is now occurring in construction and engineering fields.

Currently, there are nine Class I railroads (with only four majors), down from 58 in 1977 and 23 in 1985. 9 More mergers are expected, and some believe the United States will have just two major railroads, each providing coast-to-coast service. Mergers and acquisitions of construction and engineering firms tripled between 1996 and 1999, and even more mergers are forecast for 2000. 10

In Washington state, 30 percent of asphalt pavement is now laid by international concerns. In 1964, there were 48 asphalt pavement contractors; today, there are 18. 11

In 1985, the top 10 aggregate producers had 16 percent of the market. In 1999, they had 25 percent. 12

At the same time, there has been considerable downsizing and streamlining, most dramatically in the railroad industry. In 1977, railroads operated 309,000 miles (almost 500,000 kilometers) of track; in 1997, the total was down to 173,000 miles (almost 280,000 kilometers). 9 Between 1985 and 1997, while Class I railroad employment declined from 302,000 to 178,000, 4 ton-miles handled increased by 59 percent. 9

Economic deregulation starting in the late 1970s, coupled with information technology and the globalization of industry, has prompted a re-engineering and reorganization of service delivery and an integration of transportation into the supply chain of manufacturers. Just-in-time delivery and airline hub-and-spoke systems are illustrative of the changes. Companies are increasingly outsourcing their logistics; the World Bank reported that the share of logistical support handled by third parties for a sample of North American and European industry groupings increased by 50 percent between 1987 and 1995. 13

Competition, which was encouraged by deregulation, appears healthy despite consolidation. Rail rates (revenue/ton-mile) in constant dollars dropped every year except one in the 1989 to 1998 period, and overall in that period, the rates dropped 30 percent.14 While airlines increased their scheduled departures by nearly 20 percent from 1990 to 1999, fares in constant dollars dropped by 25 percent between 1990 and 1998. 15 Productivity is increasing. The growth of the nation's freight bill was in lock step with the growth of the gross national product (GNP) until 1981. Since then, the GNP has grown roughly 6.6 percent annually while the freight bill growth has been 3.9 percent. 13


American household garage
The average American household has almost as many vehicles as people. In 1995, the average household contained 2.65 people, and about 60 percent of households had two or more vehicles. Persons per vehicle ratio was 1.3-to-1.
[Photo credit Zac Ellis]
Public Sector

Organizational changes in the public sector have been far more modest.

Some devolution of authority to lower levels of government has occurred (with a shorter term outlook becoming even more dominant). For example, the Intermodal Surface Transportation Efficiency Act of 1991, which reauthorized federal highway and transit programs, gave states greater flexibility in the use of federal aid and gave metropolitan areas a greater voice in how that aid would be spent in their regions.

About half of the state departments of transportation have reduced their staffs. 16

Outsourcing of design and maintenance services is on the rise. Some experimentation with design-build for new facilities -- for example, I-15 in Salt Lake City -- is taking place, but there is little true privatization.

Little interest has been shown in consolidation, which would face significant barriers, and financing of publicly provided transport infrastructure and services is a continuing problem.

The inflation-adjusted state and federal gas tax at 1.6 cents per vehicle-mile in 1995 is near an all-time low. For comparison, it was 4.5 cents per vehicle-mile in 1965, and 2.5 cents in 1985. 17 The average price of gasoline, including taxes and adjusted for inflation, is also near an all-time low, lower than it was just before the 1973 oil embargo. 18

This illustrates the irony of recent efforts in Congress to repeal 4.3 cents of the federal gas tax because of recent spikes in the price, and it makes one wonder about how highways will be financed when hybrid or alternative-fuel vehicles are introduced on a large scale.

In California, highway expenditures per 1,000 vehicle-miles traveled have declined steadily for operations and maintenance -- $15 in 1956 to $7 in 1995 -- and for capital -- $45 in 1956 to $16 in 1995. 17

In summary, dramatic institutional and organizational changes have occurred in the private sector, resulting in productivity benefits. In the public sector, change has been more limited with some devolution and increased outsourcing, and big revenue questions are looming for the future.

Capacity of Existing Systems and Congestion

Transport capacity, at least in terms of the physical infrastructure, did not keep pace with demand in the latter part of the 20th century.

Between 1980 and 1997, highway lane-miles increased by 4 percent; registered motor vehicles increased by 31 percent; and vehicle-miles traveled increased by 67 percent. 19 The Texas Transportation Institute estimates that the average annual hours of delay per vehicle in the largest U.S. urban areas increased between 100 percent and 300 percent from 1982 to 1997. 20

While the railroads have shed unnecessary assets and employees and have improved productivity, the Bureau of Economic Analysis reports that real net capital stock has declined in value and that capital spending has not kept pace with depreciation and retirement. 21 Also, average speeds on Class I railroads increased between 1980 and 1992, and then began to decline. 22

Waterways and ports are experiencing capacity problems related to aging equipment, mismatches with new technology (container ships, deeper draft ships, double-stack trains), and controversial environmental issues (dredging and disposal of the spoils). Yet, international maritime demand is growing as a result of globalization. For example, containers handled at Los Angeles-Long Beach increased by 80 percent from 1990 to 1997.

In aviation, Denver International Airport is the only new air carrier airport built in the past 25 years, and our air traffic control system still relies on vacuum tube-based technology.

In summary, capacity growth has not kept pace with traffic growth of passengers and freight. Loss of redundancy and "excess" capacity are the flip side of greater efficiency, but they raise concerns about our vulnerability to major system disruptions (such as the floods in the Midwest several years ago), the cost of routine incidents, and our ability to sustain economic growth. The United States still has plenty of system capacity but not necessarily where we want it.

The Human Dimension -- The Wild Card

Transportation systems are operated for and by people, and it is the human dimension of transportation that introduces a great deal of unpredictability about the future. It is the "wild card." How will people's expectations and tastes change, and how will they adapt to new circumstances?

Cars on highway
According to the Texas Transportation Institute, the average annual hours of delay per vehicle in the largest U.S. metropolitan areas increased between 100 percent and 300 percent from 1982 to 1997.
[Photo credit Zac Ellis]

Changing Expectations

In a nutshell, Americans want it all -- more mobility, more accessibility, more personal space, a better environment, and so on -- and in the future, there will be more of us wanting these things. Without a major crisis that galvanizes public opinion and forces a major policy change, we can expect a continuation of current trends -- increasingly stringent environmental regulations and a thirst for space and mobility. Our consumer society will become increasingly more customized with more special orders, more deliveries, and more travel. Almost certainly, transport infrastructure will not keep pace with travel demand.


How will Americans reconcile these conflicting desires; deal with congestion; and, in short, "adapt"?

We have all seen dire forecasts of future traffic and gridlock based on extrapolations of current trends that are simply not realistic. Travelers will find ways to avoid regular two-hour commutes. Indeed, Americans have already demonstrated remarkable ability to adapt to changes involving their transportation options and to optimize their own happiness and preferences, sometimes in unanticipated ways. Highway capacity has increased steadily as drivers have been willing to tolerate shorter gaps between vehicles when operating at high speeds. Freeway lane capacity was reported to be 2,000 passenger cars per hour per lane in the 1985 edition of the Highway Capacity Manual; 2,200 in the 1994 edition; and 2,300 in the 2000 edition. The estimated speed at 1,800 passenger cars per hour per lane was 48 miles per hour (77 kilometers per hour) in the 1985 edition and 59 mi/h (95 km/h) in the 2000 edition. 23

Average home-to-work travel times have been surprisingly stable despite growing highway congestion. The overall average travel time rose from 21.7 minutes in 1980 to 22.3 minutes in 1990 while there was a steady rise in congestion as measured by the Texas Transportation Institute index. 6,20 Presumably, the modest growth in travel time is a result of individual adjustments in residential location, employer's location, time of travel, or choice of mode.

After the Northridge earthquake, many commuters in the Los Angeles region were forced to change routes and time of travel. Twenty-five percent said that they would stick with their new, mostly arterial, routes after repairs on damaged roads were completed.24

The aviation system has handled growth in airline traffic through introduction of hub-and-spoke operating systems and through the introduction or expansion of service at smaller airports -- for examples, Burbank, Orange County, and Ontario in the Los Angeles area and Newburgh in the New York region.

As our options and our expectations change, Americans will reconfigure residential locations, work and travel habits, and lifestyle more broadly in ways that may not be obvious to us today. These adaptations will alleviate congestion. But this does not mean that no new infrastructure is needed, nor does it mean that the tradeoffs and choices individuals make will be desirable for society at-large.

Proposals and Alternative Visions for the Future

Let me make some observations about some proposals, options, and alternative visions that have been offered for transportation in the future.

Smart Growth and Other Development Options

Highway Damage in Los Angeles
The widespread damage in the Los Angeles area caused by the Northridge earthquake in 1994 forced many commuters to find alternative routes and/or travel at different times. When the damage was repaired, about 25 percent of the commuters preferred to continue using the alternative routes.

Some people envision new land-use arrangements as a means of reducing travel demand and at the same time promoting more livable communities. "Smart Growth" and similar proposals usually envision more compact, denser residential areas, perhaps mixed with other land uses linked to public transportation. The trends previously discussed suggest that Americans will continue to place a great deal of emphasis on quality of life -- space, escaping crime, education, and personal mobility. Certainly, these things can be compatible with Smart Growth, but I suspect that "in fill" will occur more in the areas between major metropolitan areas rather than within them as employment shifts, with the aid of information technology, to small- and medium-sized metropolitan areas and rural areas. These areas can often accommodate growth with existing infrastructure or offer a more hospitable environment for infrastructure expansion.

With that said, we can and should do a much better job of designing our communities, giving more emphasis to aesthetics, environmental compatibility, and the community impact of roadways. How to best do these things is not so clear.

The Portland urban growth boundary, for example, has had some success in promoting in-fill, increasing density, and reducing land consumption. Apparently, it has also increased housing prices and reduced low-end housing availability. All of these results are to be expected.

Also to be expected is difficulty in determining when and how to extend the boundary as an metropolitan area's population increases. Without a market mechanism in place to make adjustments automatically, adjustments depend on regulatory change, which can be politically contentious and erratic.

High-Speed Trains and Maglev

Proposals for new high-speed trains, such as the French TGV (train à grande vitesse) or Japanese bullet train, and magnetically levitated (maglev) systems in the United States have been advanced many times over the past 15 years.

The development of extensive networks of such systems face significant barriers, including:

Yet, public interest in high-speed trains and maglev systems remains strong. When a special Transportation Research Board (TRB) committee looked at this topic, it suggested that selected new high-speed maglev rail lines that are integrated with the air system would be more promising than extensive high-speed rail or maglev networks. 25 Rail lines in corridors with high air traffic volumes, such as San Francisco to Los Angeles, might substitute for added airport capacity. But they would require unprecedented intermodal and public-private partnerships, and this, in and of itself, poses a significant hurdle.

More promising is another idea endorsed by the committee: incrementally upgrading existing passenger rail lines with electrification, selected alignment improvements, track improvements, and "tilt trains," such as Amtrak's new Acela, which will tilt as it goes around curves to increase passenger comfort by lessening the effects of centrifugal force. We have already seen the application of this less costly approach for high-speed rail service in the Northeast corridor.

Privatization and Outsourcing

Some analysts argue that we will get added highway capacity by privatizing the highways and will have more transit service by privatizing public transportation agencies.

For highway construction and maintenance services, increased outsourcing and innovative procurement that transfer risk to the private sector are likely -- maybe even inevitable -- given limits on public agency employment and salaries and the push for greater cost-effectiveness. Consolidation in the construction industry would facilitate this shift because larger firms are more likely to embrace innovation for competitive advantage and they have the resources for research and for accepting the added risks of warranties and design-build approaches.

Nevertheless, true privatization is unlikely; it requires firms that can adjust supply and prices in response to demand. Also, in the case of highways, government is unlikely -- or unable -- to relinquish control over decision- making regarding capacity and the tradeoffs with environmental and community impact.

For transit, the possibilities for privatization and a broader array of private-sector services are more promising. Various European countries are reporting successful applications. In the United States, labor protections and the difficulty of changing established local institutions might limit creativity in establishing and designing new private-sector services.

Intelligent Transportation Systems (ITS)

For the past decade, a federally supported effort has been underway to accelerate the development and introduction of systems that use computer, information, and communications technologies to improve the performance of transportation systems. A variety of applications are promising, including more than can be enumerated here, but I will mention two highway applications for illustration.

Photo by Federal Railroad Administration
A special Transportation Research Board committee suggested that selected high-speed magnetically levitated rail lines that are integrated with the air transportation system would be a promising substitute for increased airport capacity.
[Photo credit Federal Railroad Administration]

Advanced traffic control and management systems built upon earlier computer-based traffic systems seem certain, at least from a technical standpoint, to offer a steady stream of incremental improvements in highway service levels on congested urban roads.

Real-time performance measurement and information dissemination giving drivers accurate real-time information about travel times (or speeds) on their intended routes and providing incident information via in-vehicle devices, the Internet, or variable message signs will benefit travelers immediately. In the long run, such information may produce better informed, more demanding customers, who are more supportive of public investments in operational improvements when they deliver real benefits.

Following up on that last point, right now ITS improvements that can be implemented unilaterally by the private sector are the only improvements with a clear path to implementation. Many promising applications will require strong, continuing commitments from local governments, which unfortunately are often unable to provide the resources necessary to maintain and operate existing systems. Until such funding commitments are made and local and state governments within the same region are able to act cooperatively with seamless systems, it will be difficult to realize the full potential of ITS.

Road Pricing

Under various names such as congestion pricing and value pricing, charging motorists variable fees to use highways based on the level of demand or congestion has been advocated by some economists since the 1920s. More recently, it has been embraced by environmental organizations and policy analysts who see it as an effective way of dealing with congestion. A special TRB study committee concluded that road pricing is technically feasible and could produce net benefits to society. However, implementation would require addressing a complex set of institutional issues, and even then, it would face uncertain political feasibility. 26

In addition to likely public resistance, institutional and political issues include the details in the scope (e.g., limited-access roadways only, all primary arterials), collection methods, price-setting algorithms, allowable uses of the revenues collected, and equity across income groups. As a way to get started, the TRB committee supported HOT (high-occupancy and toll) lane experiments, such as state Route 91 in Southern California on which single- occupant vehicles pay variable congestion-based tolls to use high-occupancy lanes.

New Automobile Technology

For the past 30 years, the United States has relied heavily on cleaner engine technology, driven by more stringent regulations, to reduce or limit air pollutant emissions. Given the growth in motor vehicle travel cited previously, the record has been remarkable as demonstrated by the changes in tons of pollutants emitted by all sources between 1970 and 1997: 4

Nonetheless, more must be done as the increase in traffic growth threatens to overwhelm the gains made through cleaner internal combustion engines. This, in fact, has already happened with fuel consumption. Between 1970 and 1996, average fuel economy increased from 13.5 miles per gallon (5.7 kilometers per liter) in 1970 to 21.3 miles per gallon (9 kilometers per liter) in 1996, but total fuel consumption for motor vehicles increased 59 percent. 4 And of course, carbon dioxide emissions, which are linked to global warming, are directly tied to the amount of petroleum fuel burned.

Given these trends, the most promising way to deal with emissions, including carbon dioxide, still appears to be through the continued evolution of automotive engine technology. The advent of hybrid engines; new battery technology; and, hopefully, fuel cell technology in the not too distant future is promising, but lacking is a set of strong incentives -- economic or regulatory -- for the automobile companies to aggressively develop these technologies and for consumers to purchase the cleaner, more fuel-efficient vehicles.


The trends and proposals I have discussed suggest a future America with a larger, more dispersed population -- a population that continues to rely heavily on motor vehicles for transportation. The largest metropolitan areas will continue to grow, but small- and medium-sized cities will also grow and attract service industries. In addition to perceived lifestyle advantages, the smaller cities often have underused highway capacity and a greater willingness to add more capacity if necessary. Information technology will facilitate these trends and will allow individuals to make other lifestyle adjustments that -- along with ITS, creative public transportation services, and modest increases in physical capacity -- will help Americans adapt to the choices available without gridlock levels of traffic congestion. Incremental high-speed passenger rail will be introduced in selected intercity corridors. As in the past, the nation will rely principally on new automotive technology to address emissions, greenhouse gas, and energy concerns unless a crisis occurs and leads to a new public policy environment. More consolidation will occur in private-sector transportation companies, and public agencies will outsource more of their work to the private sector.


  1. "A Dot-Com World," The Washington Post, May 17, 2000, reporting figures from Forrester Research.
  2. Dale Hayes. "E-Commerce and Transportation: A Win-Win Partnership," presentation to the TRB Executive Committee, June 2000, citing figures developed by Forrester Research.
  3. Alan Pisarski. Presentation to the Reason Foundation Seminar, Washington, D.C., October 1999.
  4. Statistical Abstract of the United States, Census Bureau, 1999.
  5. Transportation in the United States, A Review, Bureau of Transportation Statistics, U.S. Department of Transportation, 1997.
  6. Alan Pisarski. Commuting in America II, Eno Foundation, 1996.
  7. "Americans Are Less on the Move," The Washington Post, Dec. 4, 1997, reporting on Census Bureau report, Geographical Mobility, March 1995 to March 1996.
  8. Public Transportation Fact Book, American Public Transportation Association, March 2000.
  9. Paul D. Larson and H. Barry Spraggins. "The American Railroad Industry: Twenty Years After Staggers," Transportation Quarterly, Eno Foundation, Spring 2000.
  10. "Another Day, Another Big Deal," Engineering News Record, Nov. 15, 1999, reporting figures from Mergerstat, a division of Houlihan, Lokey, Howard, and Zirkin.
  11. David Spivey, Asphalt Paving Association of Washington Inc., personal communication, June 2000.
  12. Mark Towe, presentation at Texas Transportation Institute 50th Anniversary Conference, May 2000, citing figures from Warburg, Dillon, and Reed.
  13. Kenneth Gwilliam, presentation at World Bank symposium, Washington, D.C., Dec. 17, 1998.
  14. Steven Lautsch. "Reorganization of U.S. Railway Systems," Proceedings of the 5th Regular Conference of the International Federation of Port Cargo Distributors, October 1999.
  15. Entry and Competition in the U.S. Airline Industry, Issues and Opportunities, Special Report 255, Transportation Research Board, 1999.
  16. Stephen Lockwood. Factors Affecting the Future of State DOTs as Institutions, report for Project 8-36, National Cooperative Highway Research Program, 2000.
  17. Martin Wachs. Presentation to TRB F-SHRP Committee, June 2000, citing California Revenue Study.
  18. "Despite the Price, Gasoline Is Still a Bargain," The Washington Post, May 27, 2000. citing data from Cambridge Energy Research Associates, U.S. Department of Energy, and American Petroleum Institute.
  19. National Transportation Statistics, Bureau of Transportation Statistics, U.S. Department of Transportation, 1999.
  20. David Shrank and Tim Lomax. Urban Mobility Studies, Texas Transportation Institute (http://mobility.tamu.edu).
  21. Survey of Current Business, U.S. Bureau of Economic Analysis, May 1997.
  22. Railroad Facts, Association of American Railroads, 1998.
  23. Highway Capacity Manual, Special Report 209, Transportation Research Board, 1985 edition, 1994 edition, 2000 edition (pending).
  24. State of the Commute, Commuter Transportation Services Inc., Los Angeles, Calif., 1994. (See also Giuliano et al., Impacts of the Northridge Earthquake on Transit and Highway Use, Bureau of Transportation Statistics, U.S. Department of Transportation, 1996.)
  25. In Pursuit of Speed, New Options for Intercity Passenger Transportation, Special Report 233, Transportation Research Board, 1991.
  26. Curbing Gridlock, Peak-Period Fees to Relieve Traffic Congestion, Special Report 242, Vol. 1, Transportation Research Board and Commission on Behavioral and Social Sciences and Education, 1994.
  27. Pocket Guide to Transportation, Bureau of Transportation Statistics, U.S. Department of Transportation, December 1999.

Robert E. Skinner Jr. is the executive director of the Transportation Research Board (TRB), a unit of the non- profit National Academies of Sciences and Engineering. TRB is dedicated to the coordination and dissemination of transportation research. TRB maintains 430 technical committees dedicated to promoting innovation in transportation; publishes more than 150 transportation reports, proceedings, and other documents each year; holds an annual meeting attended by more than 8,000 participants; administers contract research programs on behalf of the states and the federal government; and conducts studies on national transportation policy issues. Skinner joined TRB as a senior program officer in 1983, was named director of the Studies and Information Services Division in 1986, and became executive director in 1994. Prior to joining TRB, he was vice president of Alan M. Voorhees and Associates, a transportation consulting firm. He earned a bachelor's degree in civil engineering from the University of Virginia and a master's degree in civil engineering/transportation systems from the Massachusetts Institute of Technology. He is a registered professional engineer.



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