Citation

Banks J. Transp. Res. Rec. 2009; 2124: 28-35.

Copyright

(Copyright © 2009, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

10.3141/2124-03

PMID

unavailable

Abstract

An automated procedure for analyzing cumulative flow and speed curves is described. The essential features of this method are a routine that uses a piecewise linear approximation to identify times that speed or flow changes and a set of rules to identify periods of queue discharge flow (QDF) and prequeue flow (PQF). These rules are based on speed thresholds, the duration of periods of low speed, the times congested flow is observed at different locations relative to the bottleneck, and (in the case of PQF) the regression slope of flow versus time. Results of the automated analysis are compared with those of a previous manual analysis of data from 21 bottlenecks. The automated analysis identified more, but shorter, periods of QDF than did the manual analysis, primarily because it was more likely to identify very short periods of QDF or recovery from congestion, but fewer and longer periods of PQF. Average flow for automatically identified periods of QDF was similar to that of manually identified periods, but average flow for automatically identified periods of PQF was almost always lower than that for those identified manually.