Congestion loop analysis on continuous one hour traffic volume and travel time plots linked to one minute volume speed diagrams

To analyze and manage the congested urban freeway, our previous study proposed a Continuous 1-Hour values diagram for traffic volume(Q) - travel Time (CHQT), which continuously generates plots of hourly volume and hourly average travel time, shifting the data every minute like a moving window. The CHQT expresses congestion loop shapes that differ greatly from day to day. However, this previous study did not address the theoretical consideration of the loop in CHQT. Therefore, in this paper we first visually demonstrate the high variability of daily traffic and congestion loops by showing 128-day graphs of the CHQT using data observed on several segments of the Nagoya Expressway in Japan. Next, we analyze a degree of heavy congestion expressed by using 1-minute speed and its duration contained in CHQT, as well as creating abnormal day’s CHQT such as accidents. Finally, we demonstrate that the angle of each point on the CHQT and the angle of the 1-minute q-v movement are linked and move nearly symmetrically about the horizontal axis using a mathematical formula and actual data to analyze hysteresis phenomena. We also examine a method for optimizing scale adjustment parameter for diagrams. These contribute to the efficiency of freeway management, allowing visual grasp of the various fluctuations in traffic flow.