Evaluation of Opportunities and Challenges for using INRIX Data for Real-Time Performance Monitoring and Historical Trend Assessment

State Department of Transportation (DOTs) and various transportation agencies rely on fixed, infrastructure – mounted sensors for gathering relatively accurate traffic information such as lane by lane traffic speed, volume, occupancy and vehicle classification on major freeways, highways and arterials. The cost of deploying and maintaining these sensors is however very high compared to alternatives provided by most non-traditional data streaming sources. Also, infrastructure mounted sensors do not easily scale geographically; to determine the traffic situation in an area, a large number of sensors must be installed. As a result most Traffic Management Centers optimize the placement of sensors by deploying them on major freeways and urbanized areas. This leaves little to no coverage on minor roadways and rural segments. There is a growing desire among transportation organizations and state DOTs to consider augmenting traffic data collection with probe-based services, such as INRIX, for expanded coverage under constrained budgets. The nature of traffic data collection with probes is however dramatically different from traditional data collection techniques. For example, traffic data streams from infrastructure mounted sensors are typically averaged per lane and at a single location (time mean speed). Cell phone or vehicle probe data on the other hand, averages speed of vehicles not by lanes or at a single point but rather over a specific road segment (space mean speed). Also at present, the new data stream does not provide volume and occupancy data which are important variables for traffic incident management and planning. These differences and many more affects how the new technology is applied and used to solve current traffic related problems such as incident management and roadway performance assessment. The purpose of this study is to help Nebraska Department of Roads (NDOR) take full advantage of its probe data streaming resources to support various traffic operations activities such as incident management, performance assessment, transportation planning, traveler information, etc. in spite of its limitations. The study will develop a framework for evaluating the reliability and accuracy of the data stream with respect to its usage for measurement of traffic operational activities.