■ Transportation Research Record 1804 Paper No. 02- 3545 126 Spatial Behavioral Data Collection and Use in Activity Scheduling Models Marion Kreitz and Sean T. Doherty Transport models and their practical applications are becoming increasingly more sophisticated, thus requiring more precise input data, including spatial data. The development, testing, and assessment of a survey method with which to collect multiday information on activity–travel patterns with a high level of spatial detail and accuracy are described. The survey consists of a computer-assisted, self-completing weekly household activity–travel diary survey program combined with an interactive map for spatial data input and visualization. Compared with traditional paperand-pencil surveys, more accurate spatial data is gathered through this survey, especially for activity locations, routes, and trip lengths, which a first trial on a small sample of 30 households clearly demonstrated. In addition, more details on activity and travel times were collected. Fatigue effects did not become evident, and the respondent burden was considered to be acceptable by the participants. Additional testing of the respondents’ map-handling abilities showed that people have different map-orientation aptitudes that depend on sociodemographic characteristics such as gender, income, and education. This suggests that maps incorporated in travel surveys should be adapted in different ways to accommodate different levels of map handling. Future household travel surveys, especially emerging computerized and Global Positioning System–supported methods, would appear to benefit from the integration of a spatial interface both to add detail and to reduce respondent burden. This is particularly important for activity-based or activity-scheduling surveys, which increasingly attempt to obtain higher amounts of precise and detailed information on individual behavior and choices. these techniques lies in the restricted sample of participants and, for cell phone positioning, the lack of geographic accuracy. Another possibility for spatial data collection is through retrospective methods combined with automatic geocoding of the spatial information in a computer-assisted personal interviewing (CAPI) or computer-assisted self-interviewing (CASI) survey. For example, in its Internet-based combined travel–activity and stated preference survey, the Resource Systems Group tested a geocoding module that allowed entry of activity location by respondents by street or address, nearest intersection, establishment or business name, and direct map point-and-click (4). All entries were geocoded. The same options were also implemented in the Internet-based computerized household activity scheduling elicitor survey developed by Lee et al. (5). Applications of graphically supported survey instruments with display of locations or routes showed that the graphical user interface, photos, icons, and other multimedia elements maintain the respondent’s interest and increase both accuracy and response rate. CASI methods offer the additional potential of longer reporting periods and reduced field costs, especially in light of greater accessibility and use of computerized survey instruments by the population [e.g., computers and laptop computers, personal organizers, Internet, and e-mail (6, 7 )]. An opportunity exists to develop and apply a graphical user interface (e.g., a map) that allows for the direct input by the participant of precise spatial information into the survey system. In the field of research and planning, more sophisticated travel forecasting models are being applied, thus increasing the need for more accurate data. This need refers not only to data validity but also to the precision of spatial (geographical) behavioral information. Transport modeling—as well as applied transport demand and traffic management—is increasingly in need of precise spatial information, for exact geographic location of activity locations, routes, parking search areas, and individual activity spaces. Such data are being collected either in an aggregate fashion, by induction loops or similar systems, or disaggregately by individual travel surveys. Travel survey methods can be applied during reporting periods of variable duration, and they differ according to whether they are simultaneous (online) or retrospective, computer-assisted or paper-and-pencil (PAPI), and with or without automated positioning. Simultaneous, computer-assisted automated positioning methods have already been tested in several studies, by using the Global Positioning System (GPS) (1, 2) or cell phones (3). The disadvantage of OBJECTIVES This paper describes the development and testing of a survey method for the collection of spatial behavioral data within a retrospective CASI travel survey program. A CASI approach was considered to be the most suitable because it offers the ability to store large amounts of spatial data for display and reuse, the ability to incorporate logical checks, and the opportunity to interact directly with the participant over a longer period. The primary directive for this development was the following question: “Is it possible to collect the required spatial and other information during a longer reporting period (7 days) with sufficient validity, completeness, and precision along with a reasonable respondent burden?” If so, this method could be considered for inclusion in a full activity scheduling survey software, thus incorporating both the activity scheduling and revisions as well as a spatial–temporal component. METHODS M. Kreitz, Institute of Urban and Transportation Planning, University of Technology Aachen, Mies-van-der-Rohe-Strasse 1, D-52074 Aachen, Germany. S. T. Doherty, Department of Geography and Environmental Studies, Wilfrid Laurier University, Waterloo, Ontario N2L 3C5, Canada. Two survey methods were employed to meet the objectives. The first involved an in-depth computerized activity–travel survey incorporating a geographic information system (GIS) interface to capture Kreitz and Doherty spatial information. The second survey involved an investigation of map-reading abilities. Both were meant to provide a basis for assessing the future potential of such survey methods. CHASE-GIS Development For the purpose of this research, and to compare the survey results with PAPI and other CASI survey methods, the survey software CHASE-GIS was developed. CHASE-GIS is a further development of the CHASE (computerized household activity scheduling elicitor) survey software, developed by Doherty and Miller (8) but augmented with a GIS-based graphical user interface for the collection of spatial behavior information by Kreitz (9). CHASE is a Windows-based software designed to trace household activity–travel patterns over a multiday period and to trace the underlying decision process that led to the observed patterns. This activity scheduling process is documented by recording the sequence of decisions made by individuals in order to plan, modify, and execute their final schedule of activities and travel. An initial interview is held to establish basic household sociodemographic and activity characteristics. This information is reused during the data entry process. In the course of the reporting week, a weekly schedule similar to a typical day-planner (calendar) is displayed for each household member, FIGURE 1 CHASE-GIS activity–travel entry dialogue, activity sheet. Paper No. 02- 3545 127 leaving any unplanned or unreported time blank. Activities can be added to this calendar, causing pop-up dialogue boxes to appear for the entry of activities and related travel data. In addition, the program records when and by whom such data were entered or modified, along with supplementary information on the reasons for certain choices. Previous research demonstrated that this method provides in-depth detail on observed activity–travel patterns and underlying scheduling decisions while minimizing respondent burden and fatigue effects commonly associated with multiday surveys. During the first application of CHASE-GIS, the focus was on tracing observed activity–travel patterns over a 7-day period (especially the spatial dimension) rather than on underlying scheduling decision processes. As such, many of the CHASE software’s decision tracing components were disabled to concentrate testing on the spatial dimension. This included all questions concerning the planning status of an activity and the reasons why activities were modified. All other parts and functions of CHASE remained activated. Thus, the resulting CHASE-GIS program essentially combines the tabular weekly planner view used in CHASE with a new geographic map interface implemented within the activity–travel entry dialogue. The map view includes a zoomable GIS-based vector map of the study region that serves both as a display tool and as an input tool for spatial data, as shown in Figures 1 and 2. A detailed description of CHASE-GIS is provided elsewhere (9, 10). 128 Paper No. 02- 3545 FIGURE 2 Transportation Research Record 1804 CHASE-GIS activity–travel entry dialogue, travel sheet. The survey tool captures information on both in-home (not detailed) and out-of-home activities, categorized into detailed activity purposes and sorted by categories. As travel diaries usually do, the survey included questions about the characteristics of the activities performed during the reporting period (e.g., times, type, location, participants, costs) and the characteristics of travel to the respective activities (e.g., times, means of transport, costs). Several optional questions probed travel details further, including information on multimodal trips and public transport stops used. CHASE-GIS reuses information that is common to more than one member of a household, such as means of transport, shared activities, and common activity locations. During an initial face-to-face interview, sociodemographic data are also recorded on the computer along with common activity locations as defined by the respondent and entered by using the map as entry tool. In the course of the reporting week to follow, the respondents are asked to log in at least once a day to report their activities by using CHASE-GIS. Predefined items can be chosen from drop-down lists or from the map. If necessary, respondents may define new activities, activity locations and areas, and transport (including public transport stops and lines). All spatial information can be entered by clicking on the map. For trips by personal travel modes, the most likely travel routes are automatically generated and displayed by using a fastest-path algorithm. The route can then be corrected by the user through the addition of further reference points along the route to the map. The route is then redrawn, including the new reference points, and the route length is recalculated. The information reported is automatically checked for logical consistency. Spatial information is automatically geocoded and all input is stored in a database, together with statements of when, in which way, and by whom any kind of interaction with the program took place. In the final interview, the data are checked again by the interviewer. A short interview about the user’s experience with the software also took place. All data from the initial interview, the diary, and the final interview are stored in the same database file. The map view shown in Figures 1 and 2 contains domain information such as area and street characteristics, district and street names, and an individual (private) transport net with routing information. A public transport network with lines and stops was also added to it. The map view allows the display of • Possible and chosen activity locations or areas (origin and destination highlighted); • Public transport lines and stops (automatic choice and highlighting of the nearest stops according to the chosen line, possibility to adjust these); and Kreitz and Doherty • Routes (automatically generated fastest-path routes that can be adjusted by the user; automatic route length calculation). The first application of CHASE-GIS occurred in the summer of 2000 as part of a two-stage PAPI activity–travel panel survey in the city of Karlsruhe, Germany, carried out in the course of the Mobiplan project (11). On recruitment for the second panel wave, households were asked whether they would like to participate in the second wave by computer (on a provided laptop) or with the PAPI method again. The goal was to survey 20 to 25 households in the second panel wave with CHASE-GIS instead of PAPI methods. Because of the restricted time frame of the second wave and the number of laptops available, this was the maximum number to be surveyed. A quota sample was drawn depending on the age of the oldest household member and the household size. Households agreeing to the CASI version were recruited according to the quota sample. The survey attributes for both the PAPI and the CASI surveys were identical, thus allowing the possibility of comparative analysis of the data gathered with both methods and the experiences and evaluations of the household members. Map-Handling Survey A second survey focusing on an evaluation of the graphical features of CHASE-GIS was carried out in the spring of 2001. Because some people find it harder than others to orient themselves on a map, the purpose of this survey was to identify different types of map-reading ability of persons with different sociodemographic characteristics. A total of 178 persons of different sociodemographic backgrounds were recruited for this map-handling survey. The survey involved presentation of the same map used in the CHASE-GIS survey. Participants were asked to locate four locally well-known locations on the map given by the interviewer. The time needed by a person to find the locations was recorded, as was the geographical accuracy of the results. RESULTS CHASE-GIS Main Study Between March and August 2000, 30 households were interviewed, 4 of them in a pilot study. Four laptop computers were used in the field for a 1-week duration in each sampled household. The survey was intermitted during local holidays. It turned out that 15.7% of the households that had been given the choice between both methods were willing to participate in the CASI survey and finally did so. Recruitment for the CASI version was stopped when 30 participating households, the number of households aspired to be surveyed, was reached. Statistical tests (binary logistic regression) gave evidence that at the time of recruitment, no significant differences regarding sociodemographic aspects or the mobility (number of trips per week) in the first panel wave existed between the households that chose PAPI and those that preferred CASI. The decision to use CASI, therefore, does not depend on these characteristics, and the CASI participants can be considered as a representative sample of the Mobiplan survey participants. During the computer-assisted initial interview, the same data were gathered as in the second wave of the Mobiplan (PAPI) study. Household, person, and vehicle data were already completed with the Paper No. 02- 3545 129 associated data from the first panel wave. Additional questions covered the regular activities of the household members and their frequencies. Probable activity locations of the reporting period were defined by using the map. The information was entered into the CHASE-GIS database so the data could be reused during the reporting week. After the initial interview, the software was demonstrated to the households by the interviewer, with the aid of an entry example. In addition, a manual was distributed. During the reporting week, the respondents could call a telephone help-line. The final interview included a check for complete entries and questions regarding the respondents’ experiences with and opinions about the survey tool and methods. The average duration of the initial interview was not much longer than that held for the PAPI method: • Six min (for the household and vehicle data), • Plus 20 min per household member (for the person and activity data), • Plus 15 min for the explanation and demonstration of the CHASE-GIS-software. The corresponding PAPI survey was completed by 176 households with 276 persons. Excluding pilot surveys, the main study with CASI included 26 households (40 persons). One of the respondents was unable to handle the software because of a visual impairment and instead completed the survey with PAPI methods. Of the remaining 25 households, 21 completed the 7-day diary with the survey software. One household dropped out because of lack of comprehension of the software, and three others left because of failed data entries caused by software bugs or computer glitches (mostly caused by running the software on older laptops with capacity constraints); these also completed the survey with PAPI methods. The completeness of the data achieved in the CHASE-GIS survey can be considered to be good. The 21 households provided completed 7-day diaries with all mandatory questions answered for each activity. Problems occurred mostly with questions that required more complex data entry, especially the specification of combined means of transport and route corrections. Further information was also gathered with the optional questions, such as those concerning the sequence of transport modes used, routes, and parking search areas. With the PAPI method, fatigue effects were evident in the form of statistically significantly fewer reported trips per week in the second wave than in the first wave. In contrast, with CHASE-GIS, a slightly higher number of trips was reported in the second wave, as shown in Figure 3. Additionally, with CASI, the number of reported trips did not decrease in the course of the reporting week (Days 1 to 5 compared to Days 6 and 7) as occurred with the PAPI method in both waves. The automatic routing led to a more precise statement of trip lengths. CASI participants generally stated shorter trips than PAPI participants in both waves. This may be because CASI participants gave more exact estimations in the first wave, which were confirmed by the automatic route length calculation in the second wave. Routes were automatically calculated and displayed by using the fastest route. These could be adapted by the user in case of private transport. The trip length was recalculated subsequently. For private motorized transport, 8 of 25 persons who used this mode during the reporting week took the opportunity to adapt the routes of some of their trips. Additionally, 4 of 21 persons using bicycles changed their routes as well. In the final interview, 70% of the persons using some kind of private transport during the reporting week stated that the automatic route suggestion was “mostly” correct, so that they felt no need to Transportation Research Record 1804 80 70 60 202 508 275 118 262 297 17 264 11 50 106 440 277 40 30 20 10 0 N= 39 274 CG1 MP1 W2 Number of trips per week Paper No. 02- 3545 W1 Number of trips per week 130 80 70 118 60 75 264 11 106 291 297 50 40 30 20 10 0 N= 37 271 CG2 MP2 Wave 1 Wave 2 Percent CHASE-GIS (in Wave 2) Mobiplan PAPI CHASE-GIS Mobiplan PAPI 25 21.00 19.00 22.00 18.00 50 28.00 24.00 28.00 23.00 75 33.00 29.25 35.50 29.00 FIGURE 3 Number of reported trips per week and per panel wave (W wave; CG CHASE-GIS; MP Mobiplan). adapt it. At the same time, 50% of these persons admitted that they considered the route adaptation to be “complicated.” Furthermore, the automatic geocoding of locations and routes provided additional spatial information that could not be achieved by PAPI data postprocessing, including • Precise geographical location of activity locations or activity areas (which helped differentiate activities such as hiking and pleasure driving, both of which intrinsically involve traveling as a pursuit, not simply as a means to reach an activity location); • Means of transport used, sequence, and routes; • Activity spaces for each household member, for time of day, activity type, and means of transport; and • Parking search areas and times. The accuracy of the spatial information gathered with CHASE-GIS can be measured by comparing with the postsurvey address geocoding of the PAPI questionnaires. In the second wave, 28% of the trips were not exactly geocodable because of a lack of a specific address and number statement. In these cases, only zones (e.g., city center, name of adjacent cities) were given. Because the geocoding process was performed by a private company, the remaining effort needed to manually geocode unfortunately was not recorded. Although this is not an exact means with which to assess the spatial accuracy of the software, knowing the number of cases with insufficient address statements and assessing the address reference database’s quality (which was in this case one of the best available in Germany), these figures roughly demonstrate the potential of the automatic geocoding facility implemented in CHASE-GIS. Another way to obtain exactly geocoded activity locations and routes is, of course, to use GPS (12). Details on activity and travel start and end time, duration, and—in case of public transport use or being picked up or dropped off— access, egress, and waiting times were also captured and compared. Automatic logical checks made sure that temporal statements were consistent with one another. For the PAPI survey, a comparison regarding inconsistency in reported travel times was based on the calculation of expected travel times from the average speed of the respective means of transport and the distance covered. Recognizing the tendency of PAPI respondents to round up to the nearest 5 or 10 min, only trips with a travel time of more than 10 min were taken into account. It turned out that 25% of the reported travel times showed a deviation from the expected value of more than 50% (which might be because of traffic conditions); 11.5% showed more than a 100% deviation. The latter number indicates that there may be an advantage in correct travel time reporting from automatic matching with public transport schedules or similar background data. Measures of each user’s handling of CHASE-GIS were automatically recorded by the software. It turned out that the survey participants logged into the software an average of 7.3 times per reporting week but largely did not log in daily. Log-ins predominantly took place in the afternoon (25.94%) or in the evening (66.04%). Also on average, the participants needed approximately 22 min per day for the entries in CHASE-GIS compared to about 10 to 15 min for the PAPI questionnaire. It was thought that the log-in durations could have been further reduced if the CASI participants were better trained and made fewer wrong entries. In the final interview, most comments from the survey participants were related to the map display and the entry of activity locations. Participants stated that their orientation on the map could be improved, for example, by adding selected local points of interest and landmarks to the map or by allowing magnification of the display. They also suggested the provision of an address locator. These features were eventually implemented in a later version of CHASEGIS and were tested with positive results for handling by a subsample of the main study’s participants in October 2000. The main study’s survey design and the survey instrument itself were subject to few suggestions for improvement. Overall, the survey participants assessed their experiences with CHASE-GIS as positive in the final interview. Older households and Kreitz and Doherty Paper No. 02- 3545 households without computers tended to be less positive. These households indicated that CHASE-GIS required more effort than the PAPI method, although analysis showed that the time required for data entry was overestimated in most cases. Questioned about their preferences, 84% of the households stated that they considered CHASE-GIS to be more interesting and easier to use than PAPI and that they would prefer CHASE-GIS for another survey of this kind. They explained that this would apply especially to long reporting periods following an appropriate period (about 2 days) to become acquainted with the software. Map-Handling Survey An analysis of the accuracy and time required to locate a series of locations on the CHASE-GIS map interface revealed several tendencies, some of which were statistically significant (for selected results see Table 1). The geographic precision with which the locations were to be detected was at least to the correct block. This was achieved in 43.1% of the recorded attempts. After opening the map and stating that they knew the location they had to look for, the participants failed to find the location in only 3% of the cases. Only 4 of the 178 participants did not find more than one of the given locations, 3 of them women. All 9 participants needing the most time to carry out their tasks (more than 1.5 min for each TABLE 1 Male Female Sex location) were women. No other common characteristics of these participants were evident. In further statistical tests, it turned out that women generally needed more time than men to find a location on the map while not improving the geographical precision. These findings correspond to previous studies on way-finding (13). The older and better educated a person was and the higher the income, the faster the person located the given locations. Those having a car at their disposal needed less time and achieved more precise results than those with no motorized individual means of transport. People who owned or used computers also achieved faster and more accurate results, although this may be due to their general familiarity with the survey instrument in the first place rather than to their orientation ability on maps. Given these differences in map-handling abilities across socioeconomic groups, maps could be prepared in different ways for different groups of people, in accordance with their spatial perception and style of orientation. Furthermore, special incentives and assistance for these groups could be taken into account to reduce their burden and, consequently, improve data quality. DISCUSSION AND CONCLUSIONS Results of the CHASE-GIS survey show that respondents are willing to participate in self-completing, computerized activity–travel diary surveys and consider it very interesting. The CHASE-GIS Selected Results of Map-Handling Survey All Locations Less than 20 25.9 19.0 44.9 Time Needed (sec) 21-40 41-60 14.4 4.8 15.1 7.3 12.2 39.5 60+ 5.8 7.6 13.4 % of All 50.9 49.1 100.0 Less than 20 9.4 17.5 19.3 46.2 Time Needed (sec) 21-40 41-60 8.8 2.7 12.1 3.6 10.3 3.0 9.4 31.3 60+ 1.8 8.8 2.7 13.3 % of All 22.7 42.0 35.3 100.0 Less than 20 0.8 Time Needed (sec) 21-40 41-60 0.2 0.2 60+ 0.2 % of All 1.3 Chi2: 0,009 All Locations Monthly Income (DM) 1800 ≤ 3000 3000 ≤ 5000 5000 + Chi2: 0,016 All Locations Education Secondary School Certificate High School Graduation Apprenticeship or Master University 16.1 12.6 4.6 6.5 39.7 10.8 6.8 3.0 3.8 24.5 17.6 45.3 9.7 29.3 4.1 11.9 3.0 13.5 34.5 100.0 60+ 0.8 12.6 13.4 % of All 2.8 97.2 100.0 Chi2: not significant on 95 %-level All Locations Less than 20 Computer no 0.6 ownership yes 44.3 44.9 Chi2: not significant on 95 %-level NOTE: DM refers to income in deutsche marks. 131 Time Needed (sec) 21-40 41-60 0.3 1.1 11.9 28.4 12.2 29.5 132 Paper No. 02- 3545 survey also resulted in a high level of data quality, especially for spatial and temporal information. Compared with non-computer-assisted surveys without maps, this survey technique provides • Spatial behavioral data with a high geographic precision; • More and consistent details on activity and travel times, including public transport access, egress, transfer, and waiting times; • More and consistent details on the sequence and combination of means of transport on a trip, as well as detailed information about vehicles and routes used; • Accurate trip lengths; and • Knowledge about activity chaining, for example, through information on the scheduling status of activities or the reasons for leaving usual routes. This information is of considerable use in current transport modeling applications and would be difficult to collect via conventional methods. Although the respondents initially faced greater demands in using this method, they became much more comfortable after 3 or 4 days of reporting. However, although several significant tendencies were derived from these findings, they may not be valid for all population groups and circumstances, given the small sample size of 21 households that completed the CASI survey. The experience conducting field work with laptop computers suggests that larger samples would take considerable effort. The effort for generating an application for an area larger than Karlsruhe, such as a major metropolitan area, depends on the availability of the background data. This includes at least the digital availability of the maps with private and public transport networks and, preferably, an address locator and detailed points of interest. In Germany, the former data are available all over the country but are provided by a few private companies. This makes these data extremely expensive, except when required for research purposes. In the United States, the TIGER files provided by the U.S. Bureau of the Census would meet the requirements (but could, perhaps, be improved in content). With these data available, an enlargement of the study area requires practically no effort in terms of the survey software; the background data are simply exchanged. The effort involved for the recruitment of participants increases for larger samples and study areas. The participant training and the delivery of the survey instruments do not necessarily have to be undertaken by an interviewer, which could reduce the costs for manpower. This depends on the survey method applied. The use of laptops as survey instruments requires an interviewer for the initial explanation. Other survey instruments (Internet, personal travel assistant, cell phone) do not rely on an interviewer for these tasks. Also, more people are familiar with these instruments than with laptop computers, so they may find them easier to use. Applying CHASE-GIS on the Internet is one way to permit increased sample sizes in larger study areas in the future. The integration of the spatial features employed in CHASE-GIS would benefit other innovative survey instruments that incorporate emerging technological advances. This includes the application of CHASE on the Internet (5), the incorporation of the survey software on handheld computerized devices, the use of GPS (14, 15), and the use of cell phones for survey tasks (3). The CHASE-GIS survey showed that the implementation of a map improves the completeness and accuracy of the data gathered. The map-handling survey also provides insight into the use of maps in survey instruments. Surveys with automatic positioning (e.g., GPS) may benefit further from an Transportation Research Record 1804 interface such as the one used in CHASE-GIS, because it would allow the display of automatically traced spatial data to participants for interactive updating and completion. This would be particularly useful at times when or in places where automatic positioning is disabled or lacks precision. FUTURE APPLICATIONS A main future goal concerns how to sensibly implement the spatial features of CHASE-GIS into the next generation of activity scheduling process surveys. The lessons learned in this initial application will serve to inform future versions of the programs. The challenge will be to identify the key attributes of interest and bring them together into a comprehensive survey instrument with a minimum of respondent burden. This may include detailed spatiotemporal information on observed activity and travel patterns and information on the underlying scheduling decision process that leads to the observed patterns, preferably over a multiday period. Perhaps more important, the usefulness of such data for improved model development needs to be assessed. Emerging activity-based models aim to represent individuals, their activities, and the formation of activity chains depending on their choices, thus requiring more precise spatial and temporal data than those provided by conventional methods. For example, the activity locations have to be captured with higher geographical accuracy than at the traffic analysis zone level commonly used in traditional four-step models in order to model details of activity chains (short walking trips between several minor activities or similar) within a zone. It seems clear that methods such as CHASE-GIS would provide the detail required for the purposes of activity-based models. More recently, however, activity scheduling process models have begun to emerge that aim to represent the individual planning process and, as a result, the sequence of activities over a period (e.g., a day or a week) (16–18). Their emergence is largely in response to the need to improve the ability to forecast the more complex responses to transport demand management strategies and the needs of emerging traffic flow models for more time-dependent trip matrices. Activity scheduling process models require more detailed and different spatial and temporal data than are available (19). This includes differentiation of activities into routine activities, planned activities and spontaneous activities, rescheduling behavior, and specification of parameters such as the spatial and temporal flexibility of activities. These kinds of information have to be captured in a spatial and temporal long-term perspective and with high precision (20–22). Because of the possibility of reenabling all the original schedulingrelated modules of CHASE, CHASE-GIS probably is momentarily the most suitable instrument with which to capture those items of interest. Aside from modeling applications, the spatial information provided by tools such as CHASE-GIS may be of use for spatial analysis of individual behavior. Understanding of the individual activity spaces may benefit from exact geographical information about activity locations and types. Additional potentials for analysis are offered by the visualization of spatiotemporal patterns before data discretization with a GIS, which may help in the detection of distinctive features or regularities in behavior. Knowledge about activity spaces in the context of household characteristics and urban structure may lead to a deeper insight into the generation of activity and travel demand and its execution. Kreitz and Doherty ACKNOWLEDGMENTS CHASE-GIS was developed by the Institut für Stadtbauwesen und Stadtverkehr (ISB), RWTH Aachen, Germany, in cooperation with S. T. Doherty of Wilfrid Laurier University and PTV AG, Karlsruhe, Germany. 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