Number of Lane Changes Determined by Splashover Effects in Loop Detector Counts

Lane changes are important in quantifying traffic, both for operational and planning purposes. Traditional in-lane loop detectors do not count lane changes, hence historically, traffic engineers have estimated them using other data sources. This paper provides a method to estimate the number of lane changes based on observations of “straddling” vehicles that are detected simultaneously by the loops in adjacent lanes. In the data considered here, such “straddles” correspond almost always to vehicles that are in the process of changing lane. However, many lane-changes take place between detector sites and hence do not result in straddles. The methods developed here estimate the probability distribution for the number of lane changes given an observed number of straddles. The efficacy of this approach depends on calibration issues and on the size of the aggregation period. However, in the evaluation study considered here, the number of lane changes per aggregation period varies by a factor 10, yet the proposed method gives the number of lane changes with approximately 10% error.