Standardized Data Processing

The newly enacted U.S. transportation act Moving Ahead for Progress in the 21st Century requires the reporting of highway performance in terms of congestion and reliability. With unprecedented coverage and detail, private-sector probe-based traffic data are one of the most promising sources for the establishment of a highway performance monitoring system that can track congestion and reliability on a national scale. But the data alone are not enough; many variants in the data and the data-processing procedures can cause significantly different results even from the same set of data. As demonstrated in this paper, the space mean speed feature of the probe data, the referencing of the segment locations, the frequency of data archiving, the calculation procedures, and the difference between experienced travel time and instantaneous travel time could play a role in determining the values of certain performance measures. Standardized data elements and data processing procedures should be established in the effort to use proprietary probe data to measure highway performance.