7
The Pace of Change and Innovation

From 1955 to 1965, the basic components and practice of the current trip-based four-step travel demand forecasting process were developed and implemented in cities throughout the United States. Major studies of needs for urban highway and transit infrastructure were completed, regional transportation plans were formulated and adopted, and the design and construction of new highways and transitways commenced.

In 1973, a national conference was held in Williamsburg, Virginia, to discuss the future of metropolitan travel demand forecasting. As noted in the proceedings of that conference, travel forecasting procedures were developed and used to address the issues of the 1960s and support regional transportation plans necessary to design major transportation facilities. The proceedings went on to note that the major issues of the 1970s had changed and now included “demand responsive transit … parking policy, flow metering, exclusive lanes for buses, traffic control schemes, pricing policy, and vehicle exclusion zones.” Other new issues included influencing demand to conserve energy and equitable treatment of different sectors of the population. What was needed, concluded the Williamsburg conferees, were policy-sensitive modeling tools to inform decision making. The conferees were confident that many of these tools had already been developed by using disaggregate modeling procedures and could be incorporated into practice in a 3-year time frame (HRB 1973, 1).

In 1979, a classic text, Fundamentals of Transportation Systems Analysis, assured readers: “While the conventional urban transportation planning models have serious limitations, a new generation of models is now being developed. These models encompass much improved demand functions and a sounder theoretical basis for explicit travel-market equilibrium analysis” (Manheim 1979, 33).



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7 The Pace of Change and Innovation F rom 1955 to 1965, the basic components and practice of the current trip-based four-step travel demand forecasting process were developed and implemented in cities throughout the United States. Major studies of needs for urban highway and transit infrastructure were completed, regional transportation plans were formulated and adopted, and the design and con- struction of new highways and transitways commenced. In 1973, a national conference was held in Williamsburg, Virginia, to discuss the future of metropolitan travel demand forecasting. As noted in the proceedings of that conference, travel forecasting procedures were developed and used to address the issues of the 1960s and support regional transporta- tion plans necessary to design major transportation facilities. The proceed- ings went on to note that the major issues of the 1970s had changed and now included “demand responsive transit . . . parking policy, flow metering, exclusive lanes for buses, traffic control schemes, pricing policy, and vehicle exclusion zones.” Other new issues included influencing demand to conserve energy and equitable treatment of different sectors of the population. What was needed, concluded the Williamsburg conferees, were policy-sensitive modeling tools to inform decision making. The conferees were confident that many of these tools had already been developed by using disaggregate mod- eling procedures and could be incorporated into practice in a 3-year time frame (HRB 1973, 1). In 1979, a classic text, Fundamentals of Transportation Systems Analysis, assured readers: “While the conventional urban transportation planning models have serious limitations, a new generation of models is now being developed. These models encompass much improved demand functions and a sounder theoretical basis for explicit travel-market equilibrium analysis” (Manheim 1979, 33). 122

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The Pace of Change and Innovation 123 In 1982, a national conference on travel analysis methods for the 1980s was held in Easton, Maryland. The proceedings from this conference noted that “the gap between the state of the art and the state of the practice is consider- ably wider now than in the 1970s. . . . This has occurred while the state of practice has not improved appreciably.” The state of the art for travel analy- sis, on the other hand, was “generally well-advanced and capable of dealing with issues likely to need attention in the 1980s.” This was seen as particularly true because of the development of superior tools using disaggregate mathe- matical techniques and the adoption of methods from behavioral science. The only rub was that practitioners were not using these tools (TRB 1983, 3). In the early 1990s, the National Association of Regional Councils com- missioned Elizabeth Deakin and Greig Harvey to prepare a manual on travel modeling practice for air quality analysis. This initiative was occasioned by the Clean Air Act Amendments of 1990, which provided a regulatory impetus for accurate travel forecasts of the impacts of transportation policies and improve- ments on reducing automobile emissions and promoting clean air. The man- ual was based on a study of metropolitan planning organization (MPO) modeling practice at that time and served as a baseline for the present study of metropolitan travel forecasting practice in 2005. Deakin and Harvey found that “advances . . . in the development and application of land use and trans- portation forecasting technologies were made in the 1970s and ’80s, but only a few MPOs had the resources at that time to implement these advances.” As in the 1960s, 1970s, and 1980s, the MPO models used in practice were found to be generally incapable of adequately addressing parking policies, pricing strategies, improvements in traffic operations, and land use and urban design measures. Moreover, there were new air quality planning requirements for estimating link-specific hourly traffic volumes and speeds that were beyond the capabilities of any regional model (Deakin and Harvey 1994, 2). In 2005, this committee undertook a comprehensive survey of current metropolitan travel forecasting practice (see Chapter 4). As in the 1970s, 1980s, and 1990s, with few exceptions, MPO travel forecasting models remained aggregate, trip-based, and structured into four sequential steps. The models remained reasonably well suited to estimating the scale and location of major capital improvements. In 2005, as has been true for the past four decades, these models could not provide accurate information to inform decision making on many transportation and land use polices or traffic operations projects. Improvements made to the modeling process since Deakin and Harvey’s work were primarily the result of computer hardware (faster microcomputers with

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METROPOLITAN TRAVEL FORECASTING Current Practice and Future Direction 124 larger hard drives) and software (geographic information systems). These inno- vations allow more rapid computation and better portrayal of information, but not the information needed for contemporary decision making. The practice of metropolitan travel forecasting has been resistant to funda- mental change. Every 10 years or so there begins a cycle of research, innovation, resolve to put innovation into practice, and eventual failure to effect any appre- ciable change in how travel forecasting is practiced. This sobering assessment underscores the need to break out of this cycle, using the coordinated resources of each level of government in an alliance with academia and the private sec- tor. It is time for a return to the creativity and willingness to innovate that were hallmarks of the early days in which travel forecasting was pioneered. REFERENCES Abbreviations HRB Highway Research Board TRB Transportation Research Board Deakin, E., and G. Harvey. 1994. A Manual of Regional Transportation Modeling Practice for Air Quality Analysis, Chapter 1. National Association of Regional Councils, Washington, D.C. tmip.fhwa.dot.gov/clearinghouse/docs/airquality/mrtm/ch1.stm. HRB. 1973. Special Report 143: Urban Travel Demand Forecasting. National Research Council, Washington, D.C. Manheim, M. 1979. Fundamentals of Transportation Systems Analysis, Vol. 1. Massachusetts Institute of Technology Press, Cambridge. TRB. 1983. Special Report 201: Travel Analysis Methods for the 1980s. National Research Council, Washington, D.C.