Person-based GPS component: preparation of the next french NTS (ENT 2007)

1. Person-based GPS component: preparation of the next french NTS(ENT 2007) Philippe MARCHAL, Shuning YUAN and Pierre-Olivier FLAVIGNY, INRETS-DEST Cost 355 – Watch, Budapest WG3 Meeting, 27/04/06

2. « The travel behaviour researcher faces GPS data like a child faces a candy store – there is so much there, that it is difficult to get started » Schonfelder, Wolf, Oliveira, Samaga, Axhausen

3. Contents 1. Advantages and difficulties of a GPS Component 2. Organisation inside french NTS (ENT 2007) 3. Data-processing tools development : - Visualization aspects • Data reduction • Data enrichment 4. Next steps

4. 1. Advantages and difficulties of a GPS Component

5. Improvement of travel data collection and new technologies Technological improvements - GPS - GSM - combined GPS/GSM - RDS Advantages - limitation of forgotten trips description - accuracy in spatial and temporal framework Improvement of analyses and forecasting models

6. GPS receivers Advances in technology - smaller units - improved precision - greater storage capacity - less power-hungry units Decrease in prices towards cheaper GPS-based surveys

7. What can be obtained with a GPS component in a travel survey Details never given by respondants in conventional surveys - Description of very short trips - Speed - Route choice - Precisions on access/egress time, waiting time Travel data linked to their context : time-use, activities chaining Extended survey duration

8. Difficulties of a GPS component • Post-processing difficulties • Confidentiality problems: do exist with « conventional surveys »… but anonymizing methods have to be designed (in case of sharing of precise data) • Acceptability by respondants (cultural aspects… )

9. 3. Organisation inside french NTS (ENT 2007)

10. Context: preparation of next 2007 National Travel Survey in France « Preserve the comparability (with previous surveys), but introducing innovations to improve the quality of collected data» • 5th « Enquête Nationale Transport » realized in France, first one in the sixties (1966-67, 1973-74, 1981-82, 1993-94) • Objectives: the knowledge of households trips, for persons living in France, and of their use of transport means, both public and individuals

11. Global structure of the GPS data collection chain At the beginning of the survey : the interviewer receives a « GPS pack ». When a respondent agrees with the GPS option, 4 steps : 1) First face-to-face interview : the interviewer gives the « GPS Pack » to the respondent (volunteers only) 2) Second face-to-face interview : the respondent gives the « GPS Pack » back to the interviewer. 3) Immediately : the interviewer downloads the GPS data on his laptop computer (Bluetooth transfer), for a brief addtitional interview. 4) The interviewer checks the GPS unit, reloads it : the equipment is ready for a new interview (step 1)

12. CAPI-GPS design: additional questions (1/2) a) A first serie of n questions concerning recorded trips For each selected trip from 1 to n : Prompted recall with trip caracteristics (day of the week, date, departure time, duration, nearest origin and destination points, time spent) and follow these questions : Question 1 : « What is the purpose ? » (simplified, as compared to the main CAPI) Question 2 : « Number of accompanying persons ? »

13. CAPI-GPS design: additional questions (2/2) Question 3 : « Transport means successively used ? » (simplified set of items as compared to the main CAPI) b) Another serie of m questions concerning days without any record Question 4 : « During this day, we had no recorded data, could you precise the reasons : - I’ve forgotten the GPS unit (or unit off) - No trip - Problem with the GPS unit (battery)

14. Principle of selection of the detailed trips Selection based on the analysis of downloaded GPS data. The main idea : avoid asking the same question twice (as compared to the traditional CAPI). Systematic elimination of : • Trips corresponding to the day before the second face-to-face interview - Trips corresponding to last week-end We will also eliminate : - Trips « very similar » to the day before the second visit - Other « doubled trips » : occuring successively during several days

15. 4. Data-processing tools development : Visualization aspects- Data reduction : recording segmentation by trip or segment of trip- Data enrichment : reverse geocoding, nearest points of interest

17. Trips segmentation steps (1/2) • Initial GPS data conversion to ascii format • Ascii format to database format • Additional fields estimation • Filtering of invalid records • Segmentation by date

18. Trips segmentation steps (2/2) • Initial segmentation by trips • Elimination of records at a certain destination, during an activity • Generation of trips and stops tables

19. Indicator used : HDOP Satellites with a « good » distribution : HDOP low Satellites with a « bad » distribution : HDOP high

21. 4. Next steps

22. Short term tasks GPS-CAPI design, coupled with the data transfer program

23. Medium term tasks Improvement/validation of the traces segmentation tool Add « moving map » functions : replay recordings Rough identification of modes

24. Longer term tasks Missing data and estimations :automated reconstitution of continuous sequences, in space as in time (omissions, technical difficulties) L’enrichissement des données: methods for mode detection, transfer places and purpose estimation

25. Questions ?