Publication:
Utilization of vissim towards identification of appropriate location for queue detector at signalized roundabouts: a case study of Amman City, Jordan

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Date
2023-06-01
Authors
Amani Abdallah Ali Assolie
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Research Projects
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Roundabouts are one of the main traffic components in Amman used to improve traffic flow, but it has resulted in very serious congestion problems leading to long queues, delays, and accidents, especially in peak hours. Roundabouts are extremely beneficial when flows are balanced, but as flows rise, there may be operational challenges. When roundabouts reach their capacity, they should be upgraded to signalized intersections to maintain efficient traffic flow, but this can be costly. Alternatively, using adaptive signals and queue detectors can be a more cost-effective solution.This study aims to identify the appropriate locations of queue detectors at the selected roundabout in Amman, Jordan using micro-simulation (VISSIM) supported by programming (Python) software, and to validate the simulated models with the best level of service (LOS). From eight roundabouts located along the Zahran Road, only the 3rd roundabout King Talal Square Roundabout), the 5th roundabout (Prince Faisal bin al-Hussein) and the 6th roundabout (Prince Rashid bin Hassan), were used for simulation purposes. The queue detectors (across 15 distinct scenarios at various distances) and standard (base scenario, 50 m from the stop line) locations were assessed for appropriate placement. The model validation was made based on all scenarios including signalized and un-signalized roundabouts. The best-case scenario for queue detector location was determined based on the highway capacity manual (HCM) criteria for measurement of effectiveness (MOE) at roundabouts. The appropriate location was measured based on the value of cycle length, the duration of traffic delay (seconds), average queue length (m), and LOS. The appropriate queue detector’s location was observed to be 97 m from the roundabout stop line. The findings show that, by installing the queue detectors at appropriate locations can reduce traffic delay (or speed up the traffic flow) by 85.25% with 90 seconds of cycle length. The average queue length can be reduced up to 76.76% at the main roundabout. The LOS F status on the selected roundabouts can be improved to LOS D. Overall, the application of adaptive signal and queue detectors in the appropriate location at all approaches of roundabouts are a crucial role to improve imbalanced traffic flow whilst reducing delays.
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