Faculty Publications
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Publications by NITK Faculty
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Item A Two-Class Continuum Traffic Flow Model Considering the Disordered Behavior at Nodes(Springer Science and Business Media Deutschland GmbH, 2024) Nair, P.; Abhiram Naidu, M.N.; Sreekumar, M.A peculiar feature of smaller vehicles in multi-class disordered traffic flow is higher maneuverability and lower time of travel. The smaller vehicles can move through the gaps between larger vehicles and reach the downstream end faster. Such features of smaller vehicles contradict traditional concepts of traffic flow such as First In First Out and car following theory. On account of the distinctive features of smaller vehicles in multi-class disordered traffic stream, a macroscopic model is developed for urban corridor incorporating the two-wheeler specific features. The model captures the overtaking and creeping behavior of two-wheelers under congested conditions. The study formulates a multi-class continuum model by combining the link and node model. The link model formulated in this study comprises the fundamental relations of traffic flow with the concept of traversable distance incorporated in the equilibrium speed function to capture the two-wheeler dynamics. The output of the link model is used as input to the nodes, and node model is formulated by defining the supply and demand functions based on the type of intersection. The two-wheeler specific behavior at the intersections is reproduced through the queue formation and dissipation during congestion by simulating the traffic stream under varying external conditions. For this, the study presents four test cases to interpret the typical creeping behavior of two-wheelers at signalized and unsignalized intersections. The difference in class-wise travel time is computed, and it is observed that the travel time and delay of two-wheelers is lesser than that of cars even in congested conditions. The model is also used to demonstrate the typical bus bunching problem at intersections. The study emphasizes on the necessity for an extensive representation of two-wheeler specific features at intersections. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Dynamic Traffic Assignment Using a Multi-class Continuum Model for Disordered Traffic(Springer Science and Business Media Deutschland GmbH, 2025) Nair, P.; Sreekumar, M.The traffic conditions in urban area consist of different vehicle types, which results in varying traffic dynamics for each vehicle class. The smaller vehicles can overtake larger vehicles and also move through the gaps between larger vehicles to traverse faster. The distinct dynamics of smaller and larger vehicles is a challenge to the traditional traffic assignment models which lack class-specific behavior. The routing of vehicles based on the travel time should capture these class-specific features to have a holistic view regarding typical urban traffic conditions. Traditional traffic assignment methods fail to reproduce conditions such as congestion, queue spill back, and bottleneck regions, thereby resulting in underestimation of real traffic scenarios. This study proposes a multi-class dynamic traffic assignment framework for disordered traffic to overcome the limitations of traditional traffic assignment. The framework is tested for different traffic conditions to deduce the class-specific behavior in multi-class traffic conditions. The results from the dynamic traffic assignment are compared to the traditional traffic assignment to account for the difference in travel time computations. The travel time plots obtained using dynamic traffic assignment shows that the vehicles can overcome low to mild levels of congestion by exhibiting overtaking and creeping behavior. This stands close to real traffic conditions where there is no much change in travel time unless heavy congestion. Thus, study justifies the necessity of class-specific features in travel time computation. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Applicability of DTA Framework for Traffic Control and Transport Planning Applications on Networks with Significant Share of Two-Wheelers(Springer Science and Business Media Deutschland GmbH, 2025) Hameed, H.; Minnamreddy, H.K.R.; Nair, P.; Sreekumar, M.Urban traffic comprises of a major proportion of two-wheelers which have greater maneuverability to traverse through congested conditions in disordered traffic. These peculiar features are generally not accounted for in the traffic flow models used in dynamic traffic assignment. The applications pertaining to planning and control operations are highly dependent on the class-specific features of the traffic. Two different applications of dynamic traffic assignment are presented—dynamic wireless charging lane implementation and combined dynamic traffic assignment and control for two-class traffic stream. The results of combined dynamic traffic assignment and control model show that higher split of green times is required for shorter routes with more traffic based on the queue length and clearance time. The proportion of electric two-wheelers was more on the shorter routes and the number of links suitable for dynamic wireless charging lanes was computed for different proportions of electric two-wheelers as thresholds. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2025.Item Praseodymium doped ceria as electrolyte material for IT-SOFC applications(Elsevier Ltd, 2018) Shajahan, I.; Ahn, J.; Nair, P.; Medisetti, S.; Patil, S.; Niveditha, V.; Uday Bhaskar Babu, G.; Prasad Dasari, H.P.; Lee, J.-H.Praseodymium-doped ceria (PDC, Ce0.9Pr0.1O2) electrolyte material for intermediate temperature solid oxide fuel cells (IT-SOFCs) has been successfully synthesised by EDTA-citrate method. From X-Ray diffraction (XRD), fluorite structure along with a crystallite size of 5.4 nm is obtained for PDC nanopowder calcined at 350 °C/24 h. Raman spectroscopy confirmed the structure, presence of oxygen vacancies with the manifestation of the main peak at 457 cm?1 and with a secondary peak at 550 cm?1. From Transmission Electron Microscopy (TEM) analysis, the average particle size is around 7–10 nm and selected area electron diffraction (SAED) patterns further confirmed the fluorite structure of PDC nanopowder. The PDC nanopowder displayed a BET surface area of 65 m2/g with a primary particle size of ?13 nm (calculated from BET surface area). Dilatometer studies revealed a multi-step shrinkage behaviour with the multiple peaks at 522, 1171 and 1461 °C which may be originated due to the presence of multiple size hard agglomerates. The PDC electrolyte pellet sintered at 1500 °C displayed an ionic conductivity of 1.213E-03 S cm?1 along with an activation energy of 1.28eV. Instead of a single fluorite structure, XRD of sintered PDC pellet showed multiple structures (Fluorite structure (CeO2) and cubic structure (PrO2). © 2018 Elsevier B.V.Item A dynamic traffic assignment framework for policy analysis in cities with significant share of two-wheelers(Elsevier Ltd, 2024) Chapala, S.B.K.; Nair, P.; Sreekumar, M.; Bhavathrathan, B.K.High maneuverability of motorized two-wheelers amidst vehicles of bigger size and different dynamics invalidates FIFO to traverse through the gaps between other vehicles for faster mobility. The failure of existing dynamic traffic assignment frameworks with multi-class conditions to capture this behaviour results in inaccurate routing. The study proposes a simulation based two-class dynamic traffic assignment framework comprising of two-wheeler specific behaviour. These features when incorporated in the framework will add to the utility of the traditional dynamic traffic assignment framework in travel time prediction and planning level applications and is therefore relevant to regions with significant share of two-wheelers. The study gives a clear view of the effect of two-wheeler specific features on the route choice behaviour based on the dynamic travel time. The results of the study shows that there occurs an unintentional separation of vehicle classes during congestion; this effect can be utilized for a two-wheeler specific policy implication for congestion management in cities. The proposed framework can be employed in identifying the optimal provision of exclusive two-wheeler lanes. It is also observed that the provision of exclusive lanes may sometimes be counterproductive. © 2023