National Academies Press: OpenBook
« Previous: T56712 Text_65
Page 74
Suggested Citation:"T56712 Text_66." National Academies of Sciences, Engineering, and Medicine. 2008. Innovations in Travel Demand Modeling, Volume 1: Session Summaries. Washington, DC: The National Academies Press. doi: 10.17226/13676.
×
Page 74

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

different times of the day, such as the morning and after- noon peak periods. The mode choice model is the most important of the three components. We have been using a very simplistic approach to the land use elements in the model. We use data from local jurisdictions on population, employment, school enroll- ment, land use, and other socioeconomic characteristics. The Maricopa Association of Governments in the Phoenix area is leading an effort to develop a new land use model. The Pima Association of Governments will be one of the major users of the new land use model. We do not have any plans at this point to move toward the use of activity- based or tour- based models, primarily because of budget, staffing, and data constraints. We do have a number of surveys scheduled and we have an ongoing traffic count program. On an annual basis, we conduct traffic counts at 380 sites and 16 intersections. We also conduct regular vehicle classification counts. An external station survey is scheduled for 2007. A travel speed and travel time savings survey using a Global Posi- tioning System is also scheduled for 2007. We hope to conduct another household travel survey in 2008. I found the papers to be very interesting and learned a good deal about the capabilities of activity- based models at the sessions. Given the resources to develop and maintain activity- based models, however, we need to be able to show that the results are superior to those pro- duced by the traditional four- step model before we are able to make a significant investment in these models. Richard Walker Ihave been fortunate to have had the opportunity towork with activity models throughout my career. Keith Lawton, formerly with Portland Metro, has been a national leader in applying activity- based models. Hav- ing worked extensively with activity- based models, I did not really learn anything new at the conference. A num- ber of important points were reinforced and expanded upon by speakers, however. I would like to highlight a few of the points made throughout the conference. First, “one size does not fit all” in dealing with models, model forms, and the needs of MPOs. Agencies should look at the issues in their areas, as well as their staff and financial capabilities when determining the best models and techniques to use. The model approach for one MPO may be very different from the model approach for another MPO. Second, speakers described the different activity- based models available for practical application, as well as those in the development stage. In considering an activity- based model, it is important to review the ele- ments used in the models, the data needs, and the model capabilities. We are at a point where we can establish a benchmark and compare different models to ensure that MPOs select a model that best meets their needs. Third, we are seeing changes in the types of questions in household travel surveys. Rather than just simply ask- ing the standard questions related to individual travel behavior, additional questions are being included to obtain a better idea of why people are making certain travel choices. The reliability of the transportation system is becom- ing a more important issue. We are developing a regional transportation plan in Portland. With limited funding for projects, congestion, especially in the peak periods, will continue to be an issue in the area. A 20-minute trip in the off- peak period typically takes 40 minutes in the peak period. The consistency of the peak travel times is also an issue. Trip time reliability appears to be more important to commuters than the travel time. As a result, trip time reliability is also becoming an important factor in the decision- making process. We need to have trip time reliability in our modeling tools to provide accurate information to decision makers. Another important issue is assignments under satura- tion conditions. I was not able to attend the session where this topic was discussed, but clearly traffic con- gestion is a way of life in urban areas. As a result, assign- ment techniques with saturation are very important. I would suggest using the word “challenges” rather than “obstacles” in describing the key issues we face in advancing the state of the practice. An important chal- lenge is that we need to be aware that activity- based models may produce different results than traditional four- step models. These differences may not be evident in the base year, but the future year results from an activity- based model will be different from those obtained through a traditional four- step model. While it is to be expected that there will be differences, it can be a challenge to explain the reasons for these variations to policy makers and other groups. We need to be very strategic in implementing activity- based models and in presenting the results. Another challenge relates to future survey methods. Issues related to cellular telephones versus land- line tele- phones, freight data, and nonresponse levels all repre- sent challenges. We are working to update our regional freight data model. Obtaining accurate data on freight movement at the zone level is difficult. Guidelines at the federal level continue to change as a result of SAFETEA- LU and other programs. Addressing new and modified guidelines and requirements related to travel forecasting for different programs and projects will continue to be a challenge. It is also important to think about key elements with the introduction of activity- based models. Examples of these elements include changes in coding, model run- 66 INNOVATIONS IN TRAVEL DEMAND MODELING, VOLUME 1

Next: T56712 Text_67 »
Innovations in Travel Demand Modeling, Volume 1: Session Summaries Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB Conference Proceedings 42, Innovations in Travel Demand Modeling, Volume 1: Session Summaries summarizes the sessions of a May 21-23, 2006, conference that examined advances in travel demand modeling, explored the opportunities and the challenges associated with the implementation of advanced travel models, and reviewed the skills and training necessary to apply new modeling techniques.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!