ITS Data Archiving: Case Study of San Antonio Transguide® Data (FHWA-PL-99-024)

This report documents: 1) the state-of-the-practice in retaining and using archived ITS data, and 2) lessons learned from case study analyses of archived ITS data from TxDOT's TransGuide® center in San Antonio. The case study analyses of TransGuide® data were focused on data aggregation and data quality (i.e., data errors, missing data, and data accuracy).|The state-of-the-practice findings indicate that many operations centers are becoming more interested in archiving ITS data. Several concerns have been expressed by potential users about ITS data quality and location referencing of ITS detector locations. Analyses of TransGuide® data resulted in statistical procedures that can be used to help guide decisions about appropriate data aggregation levels. The researchers also present innovative data archiving approaches that can help to address different data aggregation needs, including capabilities such as data sampling, ondemand archiving, and data broadcasts. In other analyses, the researchers found mixed results in comparing traffic volumes from TransGuide® detectors to other nearby TxDOT traffic counting stations and ground truth video. At one location, traffic volumes from both detectors were within 5 percent of ground truth, whereas detectors at the second location ranged between 12 to 38 percent less than ground truth. In analyses of a full month of data, the researchers also found that the level of missing data was nearly 20 percent, whereas basic quality control checks flagged only 1 percent of the data as suspect or erroneous.