Development of a statewide online system for traffic data quality control and sharing.

DTRT07-G-0010The Washington State Department of Transportation (WSDOT) operates thousands of Inductive LoopDetectors (ILDs) on the freeways and highways of Washington State. The collection and disbursement ofthis data is handled at the regional level, which has led to formatting differences and data fragmentation.The Datamart Project is intended to consolidate data from all regions and store it in one location easilysearchable and accessible by all authorized users. Therefore a database and a web site have been createdin a computer application called Datamart to accomplish these tasks and demonstrate the idea.Additionally, this research project has been also tasked with creating software applications for trafficsensor data acquisition and developing error detection and correction methodologies for data qualitycontrol. Error detection is accomplished in a three-step test proposed by this study to identify loopdetectors suffering from severe errors. The default conditions used by this test approach are generalenough to be applied in other states. Meanwhile, the approach also has its flexibility to use site specificparameters to optimize its performance at a specific location. These severe errors identifiable by thisapproach include wrong mode setting, cross chatting, extreme under sensitivity, and incorrect sensitivitylevel, among others. Loop detectors suffering from incorrect sensitivity levels may be adjusted by theproposed correction methodology. The correction methodology is designed to identify the true length ofthe loop detector\u2019s detection zone. Properly calibrated ILDs are generally assumed to have detection zonesizes determined by the size of the loop coil buried in the roadway. The reality is that when ILDsensitivity levels drift from their correct settings, the detection zone size changes. By using the correctdetection zone lengths, loop detector measurements can be corrected. This software-based approach isproven effective and can be retroactively applied to archived data as well.The loop error identification and correction algorithms have been implemented in the prototypeDatamart system, which is an online database system backed up by Microsoft SQL Server 2008 and theGoogle Map technologies. It is highly scalable and has the potential to add new data sources from othertransportation agencies and online analysis functions for regional transportation planning, trafficmanagement, and analysis purposes