Outlier filtering algorithm for travel time estimation using dedicated short-range communications probes on rural highways

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Outlier filtering algorithm for travel time estimation using dedicated short-range communications probes on rural highways

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Jang, Jinhwan

With increasing market penetration, dedicated short-range communications (DSRC) probes are attracting more interest in the advanced traveller information system as a way to efficiently alleviate traffic congestion. Generally, DSRC probes, thanks to their ability to directly collect point-to-point travel time, are considered to be superior to conventional point detectors. However, outlying observations are inevitable in DSRC probe data, and can erroneously indicate abnormally long travel times. In this study, a practical algorithm to filter out outliers in DSRC probe data is proposed. The suggested algorithm is divided into two parts. In the case of small sample, it uses a previous interval value to determine a valid range for current interval values; otherwise, it uses a modified median filter that uses the median and absolute deviation of current interval observations to determine the valid range. The algorithm has been thoroughly verified using various types of DSRC probe data in interrupted and uninterrupted rural highways near Seoul, Korea. Consequently, it was proven to be sufficient to overcome the deficiencies of the previous techniques.