An Evaluation of Smartphone Tracking for Travel Behavior Studies
Abstract
:1. Introduction
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- During the recruitment of participants, one would expect smartphone tracking to make people more willing to participate in surveys, given the innovative nature and reduced burden;
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- In the data collection phase, one would expect that participants entering the smartphone tracking survey are much more likely to complete the data collection period, given the reduced burden compared to paper trip diaries;
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- More detailed and more complete registration is expected to result in more reliable indicator values for travel behavior indicators.
2. Materials and Methods
- In the “survey” mode, the participant manually initiates and terminates the registration of a trip at the start and upon arrival. In this case, the user also immediately enters the transport mode and purpose of the specific trip, resulting in complete and reliable trip information (see Figure 1);
- The “background” mode applies automatic trip detection in order to decide autonomously about the activation and deactivation of smartphone tracking, without need of the participant to interfere with the app. In this case, the transport mode is estimated during the processing of the data (out of four modes: pedestrian, bike, motorized and other), resulting in segmented trip activity (time and estimated distance) with one out of four detected transport modes. Trip segments belonging to one trip are recorded as such. In the background mode, no information about trip purpose is available.
- Trips or trip legs with a distance = 0;
- Trips or trip legs with Duration ≤ 0;
- Trips or trip legs with distance < 100 m;
- Trips or trip legs with distance > 100 km.
- The recruitment of the participants;
- The completion rate of the survey;
- The impact of smartphone tracking on the resulting travel behavior indicators.
- Trip rates;
- Modal split;
- Trip purpose;
- Trip distance;
- Trip durations.
3. Results and Discussion
3.1. Recruitment of Participants
3.2. Completion Rate of the Survey
3.2.1. Number of Days with Trip Data
3.2.2. Use of the CONNECT Survey Mode and Correction Option
- The survey mode allows users to manually record their trip during travel, resulting in a higher accuracy in terms of location data as GPS logging is activated during travel;
- Direct feedback on trip details by the user is enabled through the travel diary option in the CONNECT app, providing users with an overview of their weekly travels, where trip data can be edited by correcting errors in detected trip information (e.g., travel mode) or by adding additional information (e.g., trip purpose). In this case, edited information is stored in the database as a “trip revision” and stored next to the original data, so that modifications are traceable.
3.3. Travel Behavior Indicators
3.3.1. Trip Rate
3.3.2. Trip Distances
3.3.3. Trip Durations
3.3.4. Trip Purposes
3.3.5. Modal Split
3.3.6. Comparability of the Indicators between the Surveys
4. Conclusions
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- It is important to be aware of the challenge of recruiting participants. The reduced burden on the user does not result in the anticipated increased willingness to participate. Dedicated communication or even campaigning is required to attract and motivate interested candidates. As described in [73], “it was also learned that deploying a smartphone application as a tool for collecting travel data required more support than expected. It is similar to launching a product, which should involve a multidisciplinary team, not only designers of the questionnaire and support system, but also for example staff making the interface more user-friendly”;
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- Once participants had entered the survey, however, we observed a higher willingness to complete the survey. Whereas in MOBWAL, only 29% of the participants completed the requested 3-day survey period, in GPSWAL, 83% registered at least 3 survey days and 69% even registered 7 or more days. The reduced burden leads to a more efficient execution of the survey and offers opportunities to perform longer survey periods;
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- As the methodology affects indicators’ values based on the survey, it is essential to document in detail the full process of data collection, data processing and data analysis, delivering reproducible results. These aspects need to be taken into account when describing or comparing results from different studies. Also, Prelipcean [78] and Bonnel [79] raise the issue of a lack of transparency and standardization when using (semi-)automated travel diary collection systems and the inability to understand and compare results and performances between systems or methods;
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- In order to account for these methodological differences, a combined approach of both written trip diaries and smartphone tracking is advised such that each method can complement the shortcomings of the other. Smartphone tracking has strong assets in terms of quality (exact locations, distance, duration, etc.) and period of the trip registrations but has its limitations in terms of trip characteristics (trip purpose or transport mode need to be inferred from sensor data). These aspects are better covered via trip diaries which, in return, are more laborious for participants. As applied in the GPSWAL test, the annotation of trip characteristics can also be integrated in smartphone apps but this increases the burden on users. The combined approach can contribute to improved insight on the exact methodological impact. Bradley [41] suggests that this combined approach can be used to transition gradually from diary-based to (more) smartphone-based methods across years.
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Users | Trips | Trip Legs | Kilometers | |
---|---|---|---|---|
Official survey period | 237 | 10,395 | 14,047 | 121,008 |
First campaign | 110 | 3689 | 4827 | 46,673 |
Second campaign | 145 | 6709 | 9232 | 75,034 |
Transport Mode | No Revisions | Revised | Total |
---|---|---|---|
Foot | 138 | 4 | 142 |
Bike | 27 | 0 | 27 |
Motorized | 562 | 7 | 569 |
Unknown | 0 | 0 | 0 |
Total | 727 | 11 | 738 |
Transport mode | No Revisions | Revised | Total |
---|---|---|---|
Foot | 3477 | 962 | 4439 |
Bike | 865 | 382 | 1247 |
Motorized | 5972 | 1473 | 7445 |
Unknown | 236 | 0 | 236 |
Total | 10,550 | 2817 | 13,367 |
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Gillis, D.; Lopez, A.J.; Gautama, S. An Evaluation of Smartphone Tracking for Travel Behavior Studies. ISPRS Int. J. Geo-Inf. 2023, 12, 335. https://doi.org/10.3390/ijgi12080335
Gillis D, Lopez AJ, Gautama S. An Evaluation of Smartphone Tracking for Travel Behavior Studies. ISPRS International Journal of Geo-Information. 2023; 12(8):335. https://doi.org/10.3390/ijgi12080335
Chicago/Turabian StyleGillis, Dominique, Angel J. Lopez, and Sidharta Gautama. 2023. "An Evaluation of Smartphone Tracking for Travel Behavior Studies" ISPRS International Journal of Geo-Information 12, no. 8: 335. https://doi.org/10.3390/ijgi12080335
APA StyleGillis, D., Lopez, A. J., & Gautama, S. (2023). An Evaluation of Smartphone Tracking for Travel Behavior Studies. ISPRS International Journal of Geo-Information, 12(8), 335. https://doi.org/10.3390/ijgi12080335