Faculty Publications

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Author: search.filters.author.Sreekumar, M.

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Now showing 1 - 9 of 9
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    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.
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    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.
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    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.
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    Modelling multi-class disordered traffic streams using traversable distance: a concept analogous to fluid permeability
    (Taylor and Francis Ltd. michael.wagreich@univie.ac.at, 2020) Sreekumar, M.; Mathew, T.V.
    In multi-class disordered traffic conditions, the presence of numerous classes of vehicles having different size and operational characteristics invalidates the behaviour of lane discipline. Each vehicle traverses through a series of both viable as well as accessible gaps created by other vehicles, thus defining a permeable medium. In this paper, a plausible way to incorporate the disordered behaviour on macroscopic traffic stream modelling is discussed. A new metric termed as traversable distance has been formulated for characterising this behaviour, based on field observations. Based on class-specific traversable distances that correspond to a set of incommensurate density measures, equilibrium speed functions have been redefined. Disordered stream behaviour significantly affects the scatter in the equilibrium speed–density relationship which is a key input to macroscopic traffic flow models. Results from the modified speed functions based on traversable distance proved that the proposed methodology could considerably explain the scatter observed in the fundamental diagram. © 2020, © 2020 Hong Kong Society for Transportation Studies Limited.
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    Modeling multi-class disordered traffic flow subject to varying vehicle composition using the concept of traversable distance
    (World Scientific, 2020) Sreekumar, M.; Mathew, T.V.
    Disordered traffic stream at the microscopic level can be described as a permeable medium. Each vehicle is considered to traverse through a series of lateral gaps created by other vehicles. We develop a multi-class traffic flow model that considers such viable and accessible gaps for individual vehicle classes to traverse downstream. The model accounts for the varying shares of different vehicle classes. The concept of traversable distance and modified equilibrium speed functions are used to model the interplay among multiple vehicle classes. Using a higher order finite volume approximation method, evolution for a two-class traffic stream is shown. This model replicates prominent empirical characteristics exhibited by multi-class disordered traffic such as overtaking and creeping. Varying shares of smaller vehicles affect queue formation and discharge characteristics, and have significant impacts on roadway capacity. The model also could compute dynamic class-specific travel times at different vehicular compositions more realistically. © 2020 World Scientific Publishing Company.
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    A multi-class first-order traffic flow model to explain the disordered behaviour of vehicles
    (Taylor and Francis Ltd., 2022) Sreekumar, M.; Joshi, S.M.; Mathew, T.V.; Chatterjee, A.
    Disordered traffic streams are generally characterised by the presence of numerous vehicle classes having different sizes and operational characteristics. Unlike homogeneous traffic flow, smaller vehicles percolate between the bigger ones, invalidating the lane discipline and therefore requiring a different modelling approach. Each vehicle traverses through a series of opportunities created by other vehicles that are not only viable but also accessible, thus defining a permeable medium. Our objective is to develop an analytical traffic flow model that quantifies such opportunities for individual vehicle classes to traverse downstream. Equilibrium speed functions have been redefined based on a new metric termed as traversable distance. The inter-class flow dynamics of small-sized vehicles has further resulted in a significant reduction in their travel time. © 2021 Hong Kong Society for Transportation Studies Limited.
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    An integrated behavioral approach to analyze the adoption of electric vehicles in the context of a developing country
    (Elsevier Ltd, 2023) Krishnan, V.V.; Sreekumar, M.
    Electric Vehicles (EVs) are considered the best alternative vehicular technology having the potential to cater climatic change and energy security issues of the nations. Despite various promotional policy measures, the penetration of EVs is also observed very low, especially in the developing economies in the Indian subcontinent. This demands a comprehensive analysis of individuals’ EV adoption characteristics and the review of recent literature indicated that most of the research on EV adoption solely focuses on either the psychological aspects leading to its purchase, ignoring the available alternatives or on the conventional choice modelling techniques which do not explicitly consider the psychological motivation to choose the innovative technology. Therefore, this study integrates both behaviour modelling and conventional choice modelling in order to unfold the important determinants of EV adoption in developing economies. This study was conducted in India and the results of Hybrid Choice Modelling (HCM) highlighted that latent attitudes such as marketing perceptions, EV performance, policy perceptions, and EV usage constraints are significant factors influencing the EV adoption intention of individuals. In addition, the study also revealed that on-road price, EV adoption intention, willingness to pay extra for EVs, monthly household income, and age are also important predictors for choice between EVs and conventional vehicles. The study also pinpoints that pricing the electric SUV cars below INR 17 lakhs would make people consider choosing it over the conventional one. © 2023 Elsevier Ltd
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    Assessment of Safety Orientation in Driving Skills Aligned With Performance: A Data-Triangulation Approach
    (Lund University Faculty of Engineering, 2024) Arichandran, R.; Mohan, M.; Sreekumar, M.
    Accurate assessment of Subjective Driving Skills (SDS) is crucial for improving road safety, as direct methods are often biased and do not align well with actual driving performance. This study aimed to develop an unbiased SDS assessment method aligned with driving performance. The specific objectives are (1) reducing bias in SDS assessments, (2) verifying alignment between assessed safety orientation and ground driving performance, and (3) exploring the influence of socio-demographic factors on safety orientation. A combined questionnaire and photographic speed survey were conducted among 389 experienced car drivers in Mangalore, India. Factor analysis, a Double Lane Change (DLC) test conducted on the ground with a test vehicle equipped with Inertial Measurement Unit (IMU) sensors, correlation analysis and multiple linear regression were performed. Factor analysis confirmed the two-factor structure: Perceptual-Motor (PM) and safety skills. Further, PM and safety skills scores were calculated using factor loadings, and safety orientation was determined from their difference. DLC results showed that the assessed safety orientation aligned with the ground performance. Correlation and regression analyses showed that male drivers perceived slightly higher PM skills than female drivers. PM skills decreased with age, while safety orientation increased. Academic education had no significant effect on safety skills or safety orientation. While on-road exposure improved PM skills, weekly driving distance reduced safety orientation. Formally trained drivers had slightly higher safety skills and safety orientation than lay-instructed drivers. These findings provide several valuable insights for enhancing road safety. They suggest that safety programs address overconfidence in male drivers, incorporate road safety awareness into educational curriculums, and offer enhanced training for all experienced drivers. Younger drivers may benefit from targeted safety campaigns, while professional drivers could require specialised safety programs. Regular safety assessments and refresher courses are crucial for maintaining safety awareness, particularly for drivers with higher weekly driving distances. © 2024, Lund University Faculty of Engineering. All rights reserved.
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    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