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Innovations in Travel Demand Modeling, Volume 2: Papers (2008)

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Suggested Citation:"T57054 txt_095.pdf." National Academies of Sciences, Engineering, and Medicine. 2008. Innovations in Travel Demand Modeling, Volume 2: Papers. Washington, DC: The National Academies Press. doi: 10.17226/13678.
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GPS- enabled PDA are discussed. Following that, the functional description of the data collection tool receives further consideration, with the final section presenting conclusions. STATE OF THE ART IN COMPUTERIZED ACTIVITY- TRAVEL DATA COLLECTION TOOLS CHASE (Computerized Household Activity Scheduling Elicitor) was the first computer- aided self- interview of activity scheduling behavior (Doherty and Miller 2000). The purpose was to work out a survey that was able to track down the preceding scheduling process that resulted in the definitive execution of an individual’s schedule, along with the observed activity- travel patterns as the outcome. In the past, traditional survey techniques that use diaries (e.g., paper- and- pencil techniques) were limited almost exclusively to observed patterns, provid- ing little insight into decision processes. This shortcom- ing was dealt with through the development of a multiday computerized scheduling interface. The users’ task consisted of keeping track of their scheduling deci- sions by adding, modifying, and deleting activities to their schedule as they occurred during a multiday period. The application made notes of each of these scheduling decisions, along with prompting for additional informa- tion (e.g., the reasons for these decisions, the exact tim- ing of these decisions). The prompting process was extremely complex with paper- and- pencil techniques. Initial testing results indicated that this computerized approach revealed a considerable amount of informa- tion on the scheduling process and observed patterns, while minimizing respondent burden (Doherty and Miller 2000). Many adjustments and sophistications of this method have followed the original approach, includ- ing applications on the Internet (Lee et al. 2000), devel- opment of a geographical information system (GIS) interface for location and route tracking (Kreitz and Doherty 2002), and integration of GPS in a PDA appli- cation (Doherty et al. 2001). In contributing to this line of research, the authors suggest an application that runs on a GPS- enabled PDA. Several key development issues are desire (a) to capture the dynamic activity- travel scheduling processes, (b) to reduce respondent burden, and (c) to improve activity- travel data quality. The application described in this paper captures the process of dynamic activity- travel scheduling by collect- ing first information on the activities the respondent plans to execute and then information on the activities that the respondent did execute (diary) afterwards. Next, the planning and the diary are compared, and additional information about the differences is gathered if required. ADVANTAGES AND DISADVANTAGES OF A GPS- ENABLED PDA In the past, desktop computer–assisted data collection tools were used for completing scheduling surveys; this process provided activity- travel diary data. However, these systems are not able to trace the actual activity- travel execution due to their mobility constraints. To solve this problem, one might think of a PDA with GPS technology for enhancing the data collection tool’s mobility. The potential advantages of using a PDA with GPS to supplement travel survey data collection are numerous: (a) when using a desktop computer–assisted data collection tool, the respondents have to remember the exact locations of their start and end positions whereas, with a PDA with GPS, trip origin, destination, and route data are automatically collected without bur- dening the respondent; (b) as the respondent may forget to report an activity trip, another advantage exists in recovery of unreported trips, as all routes are recorded; (c) accurate trip start and end times are automatically determined, as well as trip lengths; (d) the GPS data can be used to verify reported data; (e) both the data entry cost and the cost of postprocessing the data constitute a significant share of the total data collection cost (Zhou 2003). These costs can be reduced to a minimum with computer- assisted forms of data collection. One of the most important shortcomings of GPS tech- nology is that the system is not always reliable during the entire trip- recording period. Indeed, civilian GPS receivers have potential position errors resulting from, for example, multipath, selective availability, and the like. However, by combining the GPS data with other data sources such as location information reported by the respondent and GIS maps, these errors can generally be overcome. Another issue associated with the use of a handheld device is the storage capacity available to save the collected data. However, with ever- decreasing stor- age capacity prices, PDAs can readily be fitted with suf- ficient memory to conduct the surveys at a reasonable price. As a PDA is powered by a battery, it has to be recharged regularly, an extra burden for the respondent. To reduce the number of times the PDA needs to be recharged, an energy- conserving battery management system was integrated into the data collection applica- tion. This way the autonomy of the data collection tool can be significantly improved. FUNCTIONAL DESCRIPTION OF GPS- ENABLED ACTIVITY- TRAVEL DIARY DATA COLLECTION TOOL The central theme of the data collection tool revolves around a PDA. Compared with a typical computerized 95DYNAMIC ACTIVITY- TRAVEL DIARY DATA COLLECTION

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TRB Conference Proceedings 42, Innovations in Travel Demand Modeling, Volume 2: Papers includes the papers that were presented at 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. TRB Conference Proceedings 42, Innovations in Travel Demand Modeling, Volume 1: Session Summaries is available online.

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