4 A new activity diary format: Design and limited empirical evidence 1
4.5 Conclusion
Small diff erences in the design of activity diaries may have substantial impacts on response rates and data quality. To make a better-informed decision in the context of a large data collection eff ort, a combined diary format was developed and evaluated against two more traditional diary formats. is paper reported on the results of this small project.
Table -: Comparison of the three activity-diaries based on the questionnaire
Combi-Stage Combi-Day Stage-Day
U(c) U(s) p(cs) U(c) U(d) p(cd) U(s) U(d) p(sd) Ease of recording:
1. Activities 17.50 16.40 0.73 18.64 16.22 0.45 16.50 15.53 0.75
2. Trips 16.17 18.00 0.56 18.67 16.19 0.45 17.87 14.25 0.24
Ease of selecting correct categories:
3. Out-of-home activities 16.47 16.53 0.98 17.00 15.93 0.74 16.23 14.77 0.62 4. In-home activities 18.06 14.73 0.29 16.82 16.13 0.82 13.93 17.07 0.31 5. Transport mode 17.11 16.87 0.90 17.64 16.23 0.50 16.07 14.93 0.59
6. With-Whom 18.39 15.33 0.33 16.94 17.07 0.97 13.93 17.07 0.30
General questions:
7. Respondents sureness with correct completion
17.03 16.97 0.98 19.19 18.82 0.91 17.70 17.34 0.91 8. Trouble experienced with completion 15.69 18.57 0.38 19.47 18.55 0.79 19.70 15.76 0.23 9. Ease of taking booklet along 18.09 14.70 0.27 22.62 12.38 0.00 18.70 14.56 0.20 10. Overall ease of recording 17.31 16.63 0.83 20.72 16.28 0.18 19.03 15.31 0.24
Keeping in mind the small sample size and the nature of the data collection process, the results of the analyses suggest some diff erences between the formats. ese diff erences are essentially a function of the diff erent organizing principles adopted and design of the diary:
stage based-approach for the trip-diary format, calendar-of-time for the day-planner format and a combination for the combination format. As discussed in the introduction, selection of the appropriate diary format and indeed organizing principle is guided by three interrelated considerations, i.e. the purpose of the project and subsequent data requirements, the quality of the desired data and model sensitivity to incorrect data and, fi nally, the respondent burden. e extent to which the three formats fulfi l these considerations are discussed below.
Generally, the stage-diary format seems very useful in environments where the number of segmented trips is relatively high or where segmented trips are of particular importance to the study. e disadvantage of this approach though is that it is likely to capture less activity-related information. If the focus is placed on the stage and activity information is only collected as part of the stop, the reporting of successive activities is lost. For example, it is not possible to capture successive activities at one spatial location if no trip is made between the activities or when the respondent is busy with more than one activity, i.e. watching TV while doing the household accounts. is is a limitation because multiple activities might be conducted at other locations besides the home location such as the work location or home location of others (during a social visit).
e advantages and disadvantages of the day-planner format are almost the opposite as those of the stage-diary. It has a more fl exible approach to the reporting of multiple activities at an out-of-home location. e potential disadvantage though is with the non-reporting of short, incidental trips. For example, being at a large shopping centre and walking between shops is unlikely recorded with the calendar-of-time diary. Recording of such short trips will place a heavy burden on respondents and they may be inclined not to report trips within the same spatial setting (or perceived spatial setting). It is believed, and this study provided some evidence perceived spatial setting). It is believed, and this study provided some evidence perceived for this, that such diaries implicitly suppress the reporting of with-in site trips. Arguably, the extent to which the stage-diary format captures these trips is very much dependent on the exact defi nition and respondents but a stage-based approach may be better for reporting such short trips. Another potential problem of the Day-planner format is respondent burden. Arguably, open ended questions and continuous time intervals places a higher burden on respondents.
is was supported by the results listed in Table -. e combination format allows respondents the convenience of reporting trips on a detailed stage level while it overcomes the problem of reporting multiple activities at out-of-home activities that occurs in the stage diary.
Overall, respondents valued the handy format of the booklet.
Data quality measured by, amongst other, rounding of time, missing information and overlapping time reporting is another important consideration in travel and activity diaries.
Inexact reporting and rounding of time may have an important infl uence on activity duration estimates, schedule delay, estimates of average travel speeds, and especially the construction of dynamic choice sets and action spaces in activity-based models. In this regard, the stage- diary format seems to be the least prone to rounding of times. ere is no reason to assume, however, that the combination format will perform poorer in this respect provided that the same instructions are given to the respondent. In contrast, the reporting bias to the rounding of
time (activities and trips) found in the case of the day-planner format might be related to this specifi c format. Possibly, the rounding of times might be a natural response of individuals to a typical diary ‘look’ of a day-planner.
With respect to the overlapping of times between successive activities a calendar-of-time approach is likely to give better results than the stage-diary format. e former format seems less exposed to the occurrence of overlapping time reporting with begin times listed below each other. On the other hand, the stage-diary format involves separation of home and out- of-home activities into diff erent booklets (or parts of a single booklet) so that one may expect that consistency between out-of-home and in-home activities may be a problem. is study provided some evidence that the latter problem may occur.
e fi nal consideration used in this study is overall user friendliness and burden. Travel and activity surveys are increasingly faced with a very low and declining response rate. is trend is primarily brought about by modern society’s disinterest, increasing time pressures and privacy concerns. Design principles can go some way to alleviate some of these problems. Here the emphasis should be on designing less intimidating and complex diaries that are understandable by the entire population spectrum. Complex codes should be avoided and activity categories and other reporting options should be limited to only the necessary information. All three diaries generally adopted a very user-friendly design with uncomplicated questions. eir size allows respondents to take the diary with them on their trips although there remains a substantial doubt whether peoples actually take the diaries along (most indicated in the questionnaires that the diaries were only completed at the end of the day).
e fi nal thought concerns the generalizability of these results. As indicated from the start, the reported results relate to our sub-samples and not to a rigorously design scheme where respondents, formats, days and environments were held constant in some sophisticated manner.
Hence, we cannot rule out that some of the diff erences we found are related to such mediating factors as opposed to inherent diff erences in diary formats. Although it is not easy to readily comprehend what a more rigorous research design should look like, this was not the reason why we did not pursue such a methodology. We were interested in testing in rather general terms the diff erent layouts as part of a pre-test of the newly developed diary instrument. is is rarely done in transportation practice. Although it does require additional resources of time and money, the results did put us in a position to make a better-informed decision about the format to choose and to improve the chosen format. Hence, the contribution of the present paper, in addition to providing some experiences and limited empirical evidence about the performance of three alternative diary formats, is in demonstrating the potential value of comparing diff erent diary format in the pre-test phase of survey design. Designing alternative diaries formats can highlight problems with exiting formats given the specifi c data requirements. Moreover, a pre- survey allows researchers to identify potential problems with regard to diff erent formats but also with the main survey with respect to users experience and potential mistakes with diff erent formats, supplying the correct user instructions, identifying actual respondent actions, such as not taking the diary along while travelling, and designing to accommodate these actions.
Generally, a pre-test limits uncertainty.
Modelling activity-travel behaviour, however, requires signifi cantly more data than provided by the activity-travel diaries alone. e land use and transport environment, which provide the opportunities for activity engagement and the means to reach the activity locations, together with all the possible causal elements (household structure, institutionalised time regimes, etc.) discussed in Chapter all impact on activity-travel behaviour and impact in one way or the other, on activity and travel choices. e following chapter discuss the land use and transport data collected as well as the study area and survey response.