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64 I N N O VAT I O N S I N T R AV E L D E M A N D M O D E L I N G , V O L U M E 1 NCHRP, a consortium of metropolitan planning organi- there have been many indications from conference zations and state departments of transportation, or pos- speakers that existing practices are inadequate. Bill sibly software firms take the lead in helping bring a Woodford's session on FTA-sponsored research touched central focus to model development, testing, and deploy- on problems associated with existing traffic assignment ment. Practitioners, academics, and consultants all need procedures. Martin Wachs's presentation on the results to be involved in the process. of a recent state-of-the-practice survey indicated that I think the lack of stochastic models is also an obsta- many MPOs are behind the curve with respect to rea- cle, as is the need for techniques to conduct risk analyses. sonable modeling practice. How can we realistically At the Puget Sound Regional Council, we are just begin- bring advanced methods into practice when we are not ning a 1-year testing phase of the UrbanSim land use doing an adequate job with existing methods? model. We have an enhanced four-step model that is The TPB adheres to a multitrack model development being used to test pricing and high-occupancy toll lane process. We have an applications track, which focuses on alternatives. It appears to be working well. We are also short-term improvements to existing methods, and we conducting a new 2-day travel diary survey. We may try also have a methods development track, which focuses microsimulation tour-based modeling in 2 or 3 years. on the development of more advanced models and tech- Along with the 2-day travel survey, we have a major niques. The methods track activities proceed in parallel problem of converting all our data from the standard with the applications track so that advanced methods industrial classification system to the North American may be phased in when deemed appropriate. If resources Industrial Classification System. We are compiling a are available, I would strongly encourage MPOs to 2006 base year for UrbanSim and we will recalibrate our adopt a similar approach. We feel the "dual track" travel model to 2006. We would also like to add a approach is reasonable for incrementally phasing regionwide dynamic traffic assignment model or a sketch improvements into production when the improvements accessibility calculator, if these tools are developed. are ready. We also believe in the development of empiri- cally based models and the use of locally collected data. Ronald Milone One obstacle to moving advanced methods into prac- tice is the grueling production schedule faced by many T hank you for inviting me to offer comments on what it will take to bring advanced travel modeling meth- ods into practice. This is certainly an important and timely MPOs, which includes periodic plan updates, air quality state implementation plan and conformity work, and project planning studies. Given this busy schedule, I feel conference, and TRB is to be commended for bringing us that there must be a firm understanding about the all together. Both the practitioners and the research com- amount of time and resources that will be required to munity have a great deal to gain by working more closely develop new methods. In order to secure time and together in the coming years. Earlier, Frank Koppelman resources, our staff and board also need to understand made the interesting comment that many of the groups how the advanced methods are superior to existing involved in the planning process are increasingly talking methods. past each other and not really listening to each other. I Another obstacle to moving forward is the lack of think the same phenomenon has been occurring between observed data. Several speakers highlighted both the lack practitioners and researchers. This conference has helped of data and the limitations of existing data used in model to close the gap between research and practice, and that is development work. It is important that the data needed needed for progress in the travel forecasting field. to calibrate and validate advanced methods are clearly The Metropolitan Washington Council of Govern- understood. I would submit that understanding observed ments Transportation Planning Board (TPB) employs a data and input data is just as important as understanding conventional four-step travel demand model that is typi- the model itself. There was a great deal of discussion at cal of such models applied at most metropolitan plan- the conference about what makes one model "better" ning organizations (MPOs) around the country. We are than another model. I do not think that is a useful dis- working hard to address a wide variety of complex trans- cussion. I would submit that the "best" model is the portation issues in the capital region, and we are increas- model that is calibrated with quality data and is driven ingly pushing the travel model to go beyond what it was by quality inputs: accurate land use forecasts, accurate originally designed to do. In addition, our modeling network coding, and accurate policy assumptions. process has received a great deal of technical scrutiny, Finally, the advanced methods need to be fully trans- particularly by environmental groups. As a result, much parent to practitioners before they are used in applica- time has been spent examining and refining our methods tion. Practitioners presently understand the four-step used in application. model very well. They know how to develop four-step The motivation of this conference is to facilitate the models and how to interpret results. They understand implementation of advanced methods into practice. Yet, the limitations of the four-step approach. As advanced