A METHODOLOGY TO DISAGGREGATE SPEED DATA COLLECTED BY ROAD DETECTORS

The paper introduces an algorithm that disaggregate speed data collected with automatic road detectors which can only measure speed frequency in intervals only. The objective is to obtain back-calculated “artificial” individual speeds to operate with continuous distribution functions rather than discrete ones. This allows the derivation of more robust, basic descriptive measures (average, variance, and percentiles) according to Normal, LogNormal, and Gamma probability distribution functions. The information produced in this way is more useful than that calculated from standard aggregated speed reports and can be used for further processing purposes. In this investigation, individual speed data collected from video cameras were used to derive reference distributions and descriptive measures on the same road sections where inductive double-loop detectors were installed. The comparisons between the back-calculated individual speeds and those collected from video cameras support the validity of the proposed algorithm.