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188 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 2 monetary expenditures and types of commodities and of factors that influence service levels. A survey method services purchased at commercial establishments. These that provides timespace coordinates of an individual's kinds of data will make survey results applicable to a movement trajectory with high resolution is desired. wider range of planning studies. Third, there is a fundamental issue of whether trip This paper summarizes the results of several pilot sur- measurements obtained from conventional travel sur- veys conducted in Japan by using probe person systems. veys may be inadequate to represent an individual's It shows technical requirements for new travel behavior travel pattern in time and space. For example, accurate surveys that are based on the results of these pilot sur- measurement of travel behavior calls for the recording of veys and discusses the possibility of data-oriented travel short trips. Yet, in addition to the fact that conventional behavior analysis. questionnaire surveys have a problem with reporting omissions, it is often difficult or costly to geocode trips accurately on the basis of the information available from TECHNICAL REQUIREMENTS FOR conventional questionnaire surveys, and errors can be TRAVEL BEHAVIOR SURVEYS excessive in the case of short trips. Moreover, the accu- racy of measurements that are based on survey respon- An individual's activity and travel vary from day to day. dents' memory may be inadequately low in relation to To capture day-to-day variations in travel behavior in the current planning analysis requirements. urban space through surveys and to develop and evalu- ate alternative transportation policy measures, one would desire to IMPLEMENTATION OF SURVEY TECHNIQUES 1. Implement a long-term survey, This section covers the characteristics and problems of 2. Determine spacetime coordinates with high reso- the following five survey methods as tools to collect data lution and accuracy, and for travel behavior analysis: 3. Automatically and accurately measure detailed activity contents. 1. Questionnaire surveys, 2. Web surveys, First, to capture more accurately the diverse patterns 3. Mobile phone surveys, of travel behavior that vary day to day, it is necessary to 4. Probe-person surveys, and implement a long-term, detailed travel behavior survey 5. Surveys using multiple sensors. and observe day-to-day variations in travel patterns. A one-day survey would be sufficient if one wishes to A questionnaire survey can be administered in many acquire information on highly repetitive travel such as ways, each having advantages and disadvantages. For commuting. Travel patterns vary from day to day for example, it is relatively easy to collect data at a low cost various reasons, as noted above, and one's knowing the per completed survey but with a low response rate and a patterns of variation is a prerequisite for determining the lower quality of data in the case of mail-outmail-back causes for, and revealing the mechanisms of, day-to-day surveys. These problems may be overcome when a sur- variations in travel. This knowledge obviously requires vey involves home visits (either just to delivercollect long-term observation of travel patterns. questionnaires or to conduct home interviews) but with Second, it is desirable to determine the spacetime the much higher costs and difficulties of visiting house- coordinates of an individual's trajectory in urban space holds. Moreover, either method requires data coding, along the time axis. Gathering this information calls for which consumes monetary cost and time in proportion identifying--with high accuracy--activity locations, to the sample size. activity durations, trip starting and ending times, and the Computer-aided telephone interview (CATI) surveys like. In some planning contexts, one would also desire to have become a standard procedure in household travel determine travel routes, transfer locations, public transit surveys in the United States. It has many advantages waiting times, and the beginning and ending times and (e.g., data coding is automated, branching is automatic locations of the respective trip segments typically and error free, and questionnaires can be easily cus- involved in a public transit trip. (Even an automobile trip tomized) as well as disadvantages (e.g., it takes an exces- involves access and egress walking, yet the exact location sive amount of interview time in case of a large of parking is often ignored in conventional travel sur- household). As with conventional surveys, trip records veys.) A survey method aimed at capturing the total daily are obtained on the basis of the respondents' abilities to demand volume between zones is incapable of providing recall travel events on the survey day. The quality of the the information necessary to evaluate planning measures data also rests on the respondents' understanding of intended to manage travel demand by fine-tuning a range what exactly a trip is and how its attributes, including