Faculty Publications

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    Estimation and Comparison of Saturation Flow at Signalized Intersection in Mixed Traffic Condition
    (Springer Science and Business Media Deutschland GmbH, 2022) Mahapatra, M.J.; Advani, M.; Ravi Shankar, A.U.
    Signalized intersections are the important part of urban road network. Capacity of signalized intersections has significant role in capacity of overall road network in an area. Accordingly, capacity estimation of signalized intersection and therefore the estimation of saturation flow values become an important aspect especially for Indian roads due to the presence of different types of vehicles and space sharing-based vehicular movement. This study extracts the saturation flow from the field data captured through videography and compares it with the saturation flow values estimated by various methods available in literature. Data have been collected at two signalized intersections; first one is a four-legged intersection, and other one is three-legged intersection. Approach width of all arms of both intersections ranges from 7.6 to 10.3 m. Both intersections are located on the main arterial road of Delhi, India, and at the distance of 1.1 km without any obstructions in-between. Saturation flow has been estimated through existing methods available in literature and compared with the developed model in this study. Proposed model indicates that with the increased width, saturation flow values also increase. Values estimated are closer to values obtained by Webster’s method. © 2022, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Impact of Leading Vehicles of the Queue on Saturation Flow at Signalized Intersections
    (Springer Science and Business Media Deutschland GmbH, 2024) Kumar, R.; Mohan, M.
    Saturation flow is an essential component in the design and capacity estimation of signalized intersections. The saturation flow rate is influenced by several factors, including intersection geometry, speed limit, the proportion of heavy vehicles, parking activities, bus stops adjacent to the intersection area, lane utilization, pedestrian volume, etc. Estimation of saturation flow is well-established for homogeneous traffic conditions. However, measuring and modelling saturation flow are challenging in mixed traffic conditions due to the non-lane-based traffic flow and the presence of multiple types of vehicles. Typically, Passenger Car Unit (PCU) adopted should be enough to account for the variation among the vehicles that constitute the queue while estimating saturation flow. However, field observation at Indian intersections indicated that the vehicles at the front of the queue might profoundly influence the queue discharge at the onset of green phase, thereby exposing the shortcoming of PCUs. This influence is clearly visible when heavy vehicles make up the front of the queue and owing to their inferior operational performance and larger size, they deny the following vehicles the opportunity to attain their desired acceleration. To investigate this, the present study simulated the operation of a typical four-legged signalized intersection in VISSIM software. The subsequent analysis revealed a strong relationship between leaders of the queue and the saturation flow of the approach. This result from the simulation was then verified based on field data. The study concluded that the PCU factors adopted at signalized intersections fail to account for the effect of the queue leader’s composition, which has a marked influence on the saturation flow. © 2024, The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Investigating bus stops' influence on saturation flow at signalized intersections in heterogeneous traffic
    (Aracne Editrice, 2022) Shubhashree, K.S.; Mohan, M.
    The public transportation system efficiently reduces congestion and pollution as they lessen the dependency on personalized modes. However, most bus stops are located close to the intersection, and the stopping buses often create a bottleneck. At signalized intersections, this will seriously impact the saturation flow as it hinders the efficient functioning of the traffic signal system, resulting in delays and reduction of the intersection's capacity. Hence, a profound understanding of the factors associated with bus stoppages, which influence the saturation flow, is essential in designing efficient signalized intersections. This study simulates traffic flows at signalized intersections in heterogeneous traffic in a micro-simulation software VISSIM. Results of multiple simulation run indicated that saturation flow at intersections depends on the percentage of buses in the vehicular mix, the distance of bus stop from the stop line, and percentages of right and left-turning traffic. Further, the study proposes separate saturation flow models for upstream and downstream bus stop conditions. These could be used to optimally place bus stops near the intersection such that it does not hamper the performance of the intersection while not causing any undue discomfort to the bus passengers. © 2022, Aracne Editrice. All rights reserved.