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Issue No. 05 - May (2012 vol. 11)
ISSN: 1536-1233
pp: 849-864
Baik Hoh , Nokia Research Center, Palo Alto
Toch Iwuchukwu , Nokia Research Center, Palo Alto
Quinn Jacobson , Nokia Research Center, Palo Alto
Daniel Work , University of California, Berkeley, Berkeley
Alexandre M. Bayen , University of California, Berkeley, Berkeley
Ryan Herring , University of California, Berkeley, Berkeley
Juan Carlos Herrera , University of California, Berkeley, Berkeley
Marco Gruteser , Rutgers University, North Brunswick
Murali Annavaram , University of Southern California, Los Angeles
Jeff Ban , Rensselaer Polytechnique Institute, Troy
Traffic monitoring using probe vehicles with GPS receivers promises significant improvements in cost, coverage, and accuracy over dedicated infrastructure systems. Current approaches, however, raise privacy concerns because they require participants to reveal their positions to an external traffic monitoring server. To address this challenge, we describe a system based on virtual trip lines and an associated cloaking technique, followed by another system design in which we relax the privacy requirements to maximize the accuracy of real-time traffic estimation. We introduce virtual trip lines which are geographic markers that indicate where vehicles should provide speed updates. These markers are placed to avoid specific privacy sensitive locations. They also allow aggregating and cloaking several location updates based on trip line identifiers, without knowing the actual geographic locations of these trip lines. Thus, they facilitate the design of a distributed architecture, in which no single entity has a complete knowledge of probe identities and fine-grained location information. We have implemented the system with GPS smartphone clients and conducted a controlled experiment with 100 phone-equipped drivers circling a highway segment, which was later extended into a year-long public deployment.
Algorithms, design, experimentation, security, privacy, GPS, traffic, data integrity.

R. Herring et al., "Enhancing Privacy and Accuracy in Probe Vehicle-Based Traffic Monitoring via Virtual Trip Lines," in IEEE Transactions on Mobile Computing, vol. 11, no. , pp. 849-864, 2011.
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