Institute of Transportation Engineers (ITE)
ITE Western District (Western United States)
San Francisco Bay Area Section
Honorable Mention: 2008 Transportation Project of the Year Award
MOBILE CENTURY: A Novel Approach to Traffic Data Collection from GPS-Equipped Mobile Phones
This project, nicknamed Mobile Century, aimed to test a novel approach, enabled by recent advances in telecommunication technologies that collected data from GPS-equipped cell phones and turned it into relevant traffic information. On February 8th, California Center for Innovative Transportation (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. The goal of this controlled field experiment was to test traffic data collection from GPS-equipped cell phones driving on a stretch of a I-880 highway located in the San Francisco Bay Area.
This project is addressing Caltrans' -- and consequently other Departments of Transportation (DOT)'s -- top-priority need for expanding the scope and coverage of roadway Advanced Traveler Information System by implementing an accurate and cost-effective data collection technology.
Government agencies currently deploy networks of traffic sensors that are expensive to install and maintain. Leveraging commercial cellular networks could drastically cut the ongoing costs of traffic monitoring and expand coverage to thousands of miles of highways and urban arterials for which sensor installations are not even considered an option. 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, Global Positioning System (GPS) receiver chips are now built into more and more handsets. This technology provides very accurate speed and positioning data. Therefore, GPS appears to be the key ingredient needed to turn mobile phones into traffic probes.
The Mobile Century experiment enabled the design and development of algorithms and data collection systems to assemble traffic data from GPS-equipped mobile phones. 100 vehicles carrying the GPS-enabled Nokia N95 drove along a 10-mile stretch of I-880 from 9:30am to 6:30pm. The phones stored vehicle speed and position information every 3 seconds. These measurements were sent wirelessly to a server for real-time processing.
Overall, the average daily train ridership has been significantly increased this year, after deploying the system, ranging from 12%-27% for targeting stations. There has been a 10% increase on parking stall counts before and after the system was activated. The log data also indicates that more than 60% of time commuting with train had time advantage over driving on highways during traffic peak hours (7:00 am- 9:00 am and 5:00 pm- 7:00 pm). In general, during the existing operation schedule (5:00 am- 9:00 am and 3:30 pm- 7:00 pm) the signs showed about average 45% time advantage for using trains vs. driving.
The principal objectives for this experiment were to feature:
- Online, real-time data processing,
- Privacy-preservation, and
- Data efficiency, i.e. not requiring excessive cellular network load.
The benefits of the application that we intend to demonstrate through Mobile Century are two-fold. First, it promises to significantly lower the cost of collecting traffic information compared to what is made possible with today's technologies. Carefully designed, the collection of mobile probe data over existing cellular networks will only incur minimal incremental costs to the operations of those networks. Second, in addition to lowering costs, this method will augment coverage to thousands of miles of roads that are currently not instrumented with any kind of sensors.
The results of the project are as follows:
- The concept of using GPS-equipped cell phones as traffic probes was successfully tested.
- Smart-phone software has been developed to collect data on the phones in a privacy preserving environment.
- A data collection infrastructure has been created.
- Mobile Century experiment has demonstrated that with 2% to 5% (representing smart-phone fleet in 18 months in the United States) of the total flow of highway equipped with GPS enabled cellular phones, the system will become sustainable. The results were validated against 511.org, Performance Measurement System (PeMS) data and video data collected from the bridges.
Mobile Century could successfully accomplish all the objectives and has proven that GPS-enabled cell phones can be deployed as sensors for traffic monitoring purposes, while preserving individuals' privacy when collecting data.
Congratulations to CCIT and its partners for this Honorable Mention in the 2008 ITE SF Bay Area Awards Program.
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