Tracking daily travel; Assessing discrepancies between GPS-derived and self-reported travel patterns Douglas Houston a,⇑ , Thuy T. Luong b , Marlon G. Boarnet c a Department of Planning, Policy, and Design, 300 Social Ecology I, University of California, Irvine, CA 92697-7075, United States b Transportation Science Graduate Program, University of California, Irvine, CA, United States c Sol Price School of Public Policy, University of Southern California, Los Angeles, CA, United States article info Article history: Received 23 October 2013 Received in revised form 5 June 2014 Accepted 18 August 2014 Keywords: Travel behavior Self-report Global Positioning Systems Travel survey data collection abstract Global Positioning Systems (GPS) technologies have been used in conjunction with tradi- tional one- or two-day travel diaries to audit respondent reporting patterns, but we used GPS-based monitoring to conduct the first assessment to our knowledge of travel reporting patterns using a seven-day travel log instrument, which could reduce response burden and provide multiple-day, policy-relevant information for evaluation studies. We found substantial agreement between participant-reported daily travel patterns and GPS-derived patterns among 116 adult residents of a largely low-income and non-white transportation corridor in urbanized Los Angeles in 2011–2013. For all modes, the average difference between daily GPS- and log-derived trip counts was only about 0.39 trips and the average difference between daily GPS- and log-derived walking duration was about 11.8 min. We found that the probability that a day would be associated with agreement or discrepancies between these measurement tools varied by travel mode and participant socio-demographic characteristics. Future research is needed to investigate the potential and limitations of this and other self-report instruments for a larger sample and a wider range of population groups and travel patterns. Ó 2014 Elsevier Ltd. All rights reserved. 1. Introduction and aims Portable Global Positioning Systems (GPS) technology has been increasingly used in public health and travel behavior studies to assess physical activity and exposure to environmental hazards and amenities based on extended monitoring of activities and locations for periods often ranging from 6 to 14 days (Bohte and Maat, 2009; Chaix et al., 2013; Krenn et al., 2011). GPS has also been increasingly used to supplement traditional travel surveys, which typically use a one-day travel diary requiring participants to provide substantial information about trip purpose, mode, start and end time, and the location of the trip origin and destination (Stopher and Greaves, 2007). Requiring such detailed trip-level information can present a substantial burden for respondents and could be associated with response fatigue and lower reporting accu- racy (Golob and Meurs, 1986). In fact, comparisons of self-reported travel patterns with GPS-derived patterns indicate that participants do not report all GPS-identified trips in their travel diaries (rates of unreported trips range from 10% to 80%), that participants consistently over-report trip duration by about 4.4 min, and that discrepancies in trip measures are associated with socio-demographic and travel-behavior characteristics (Wolf, 2004; Wolf et al., 2004). http://dx.doi.org/10.1016/j.trc.2014.08.013 0968-090X/Ó 2014 Elsevier Ltd. All rights reserved. ⇑ Corresponding author. Tel.: +1 949 824 0563; fax: +1 949 824 8566. E-mail address: houston@uci.edu (D. Houston). Transportation Research Part C 48 (2014) 97–108 Contents lists available at ScienceDirect Transportation Research Part C journal homepage: www.elsevier.com/locate/trc