On February 8th, CCIT, Caltrans, Nokia, and UC Berkeley’s Department of Civil and Environmental Engineering collaborated to conduct an unprecedented experiment in the area of traffic monitoring.

The event was enormously successful, both technically and logistically.

CCIT would like to thank the entire team for their work on this labor intensive project. CCIT would especially like to thank Mobile Century's project manager Ali Mortazavi and principal investigator Alex Bayen for their excellent work.

View our news page for articles, podcasts, and more about this project.

For an entire day, 100 vehicles carrying the GPS‐equipped Nokia N95 drove along a 10‐mile stretch of I‐880 between Hayward and Fremont, California.

The phones stored the vehicles' speed and position information every 3 seconds. These measurements were sent wirelessly to a server for real‐time processing.

Cameras located on bridges at both ends of the loop recorded the actual travel times of all vehicles, including those not participating in the experiment. This provided a ‘ground truth’ reference that will be compared with the speed and position estimates produced from the GPS data.

Privacy Issues

The protection of personal privacy was built into the very core of the research project. Researchers built safeguards into the system, such as stripping the traffic data from identifiers with an individual phone, using banking-grade encryption techniques to protect the transmission of data, and drawing data only from targeted roadways where traffic information is needed. Data that can be tied to a particular phone will not be created, transmitted or stored in this "privacy-by-design" system.

Moreover, mobile device users control the service. If an individual does not want his or her device to transmit position data, he or she can turn off the GPS feed. Researchers are studying the trade-offs between personal privacy, traffic data accuracy and data collection costs.

Please Download a Mobile Century fact sheet. (PDF .5 MB)

A Larger Context

The Intelligent Transportation Systems (ITS) community has long examined the potential of using cell phones to operate as traffic data collection devices.

Available methods to collect data from cell phones rely on approximate positioning provided by the cellular networks, and have shown limited accuracy to date. However, GPS chips will soon become as ubiquitous as cell phone cameras. For example, Nokia will be adding GPS to most cell phones in the near future.

The prospect of large numbers of GPS‐equipped cell phones reporting position and speed with 10 meter / 3 mph accuracy at regular intervals represents a huge leap forward in traffic monitoring technology. Yet, its implementation requires addressing key questions regarding individual privacy, data ownership, network load, and proper traffic flow estimation techniques.