Algorithm for Detecting and Correcting Errors in Archived Traffic Data

Abstract

An algorithm is presented for correcting errors in archived loop data from freeway traffic-management systems that are the result of poorly calibrated sensors. These errors pose a significant difficulty when archived data are used in off-line analysis because the calibration errors are difficult to detect by using traditional methods. In the presented work, consistency of vehicle counts is used to judge the validity of the data: if vehicles counts are balanced, the data are valid; if vehicle counts are not balanced, the data are not valid. The method also can determine a correction factor. This correction factor is used to create a time series that can be combined with the original data to adjust the volume to create a consistent data set. To illustrate the methodology, an example case is presented that details the process of identifying a pair of reference stations that are properly calibrated. After the reference stations are identified, a poorly calibrated station is identified, and the data from this station are corrected. The result of the correction process is discussed.

Correction of Measured Traffic Volume on Expressways Based on Traffic Volume Balancing

“…When a difference occurs in the comparison, it is considered to be a violation of the traffic volume balance, and a non-linear optimization model is applied to correct the measured traffic volume. Wall and Dailey [15] established a reference detector to verify and correct the measured traffic volume on the expressway main line and set the measured traffic volume collected from this detector as the initial value. The measured traffic volume configured as the initial value was used to verify whether the adjacent measured traffic volume satisfied the traffic volume balance.…”

Method for accuracy assessment of aggregated freeway traffic data

“…Wall and Dailey [11] proposed an error detection algorithm that first identifies a pair of well-calibrated reference stations, whose historical data shows a strong conformity to the conservation principle. Subsequently, faulty sensors adjacent to the reference stations are identified by comparing with the latter.…”

Method to detect malfunctioning traffic count stations

“…In such case, the next step would be to obtain the adjusted data, that is, the consistent data that most closely resembles the observed data. Any data deemed inadmissible during the pre-process will have been eliminated from the observed data using one of the procedures suggested by other authors ( [1], [2], [3] and [4]).…”

“…A number of studies ( [1], [2], [3], [4] and [5]) attempt to find a solution to Case 1 (admissible errors)…”