Browsing by Author "Dey P.P."

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Affinity propagation clustering for quantification of level of service at uncontrolled median opening
(2014) Mohapatra S.S.; Dey P.P.; Sil G.
Level of service at uncontrolled median openings on multilane divided urban roads is not defined for heterogeneous traffic condition prevailing in India. The LOS of uncontrolled junctions is quantified by the delay experienced by the lower priority movement. Therefore, delay experienced by the lower priority movement i.e. U-turning vehicles at an uncontrolled median opening has been studied to quantify the delay ranges for different LOS categories. Recently developed, affinity propagation (AP) clustering algorithm was employed to achieve the solution of the classification problem. Five validation parameters are analyzed to get the optimal number of cluster number which is crucial for the classification of different level of service categories. Affinity Propagation clustering is used to get the delay ranges for 6 different LOS categories. The range is less than 4 second for best operating condition and is greater than 35 second for the worst operating condition.
Conflicting volume for U-turns at uncontrolled median openings
(2016) Mohapatra S.S.; Dey P.P.; Chandra S.
This paper proposes a practical approach to estimate the conflicting traffic volume caused by U-turns at uncontrolled median openings under mixed traffic conditions. Data were collected at 21 median openings on multi-lane divided roads in India (i.e. 13 on six-lane and eight on four-lane). The road width at the median opening is divided into three parts: zone of severe conflict, zone of safety and unaffected zone based on the placement of the left wheel of U-turning vehicles (left-hand drive rule followed in India). The first two zones together are considered as the conflicting zone for calculating the conflicting traffic. The proportion of opposing through traffic within the conflicting zone is considered as the conflicting traffic volume for U-turns. The conflicting volume at all the sections is estimated based on placement of through traffic across the width of the road and it is found to be dependent on the size of the U-turning vehicle. An equation is suggested to calculate the conflicting traffic based on the composition of U-turning traffic. The conflicting traffic on six-lane roads is found to be relatively, low but on four-lane roads, almost all of the opposing traffic becomes conflicting traffic for U-turns. � 2016, Thomas Telford Services Ltd. All rights reserved.
Estimation of critical gap of U-turns at uncontrolled median openings
(2019) Dash S.; Mohapatra S.S.; Dey P.P.
The estimation of critical gap is an important traffic parameter and this is useful to estimate the capacity of U-turning vehicles at uncontrolled median openings. In this study critical gap is estimated by four different methods by collecting data at seven median openings in India. During field study it was observed that, the heterogeneous traffic in India operates very peculiarly and the rule of priority is often violated and aggressive behavior of the minor stream vehicles compels the major stream vehicles to slow down to provide sufficient gap for the U-turn maneuver. These peculiar characteristics warrant for a re-look into the methodology of critical gap estimation. An unconventional method of critical gap estimation using the merging time of the U-turning vehicle is proposed. The merging time to clear the conflict area at uncontrolled median opening was calculated from field data and this time is utilized to estimate the critical gap for different categories of vehicle. � 2017, � 2017 Informa UK Limited, trading as Taylor & Francis Group.
Estimation of U-turn capacity at median opening
(2018) Mohapatra S.S.; Dey P.P.
Median openings are provided in multilane divided roads to enable U-turns. The atypical conditions prevailing in India motivated this study for the development of a methodology for the proper computation of the capacity for U-turns at these locations. Harders' formula has been widely used by various researchers to evaluate capacity for U-turns and this formula needs three elementary factors-namely, conflicting traffic volume, critical gap, and follow-up time. We collected the required data for capacity estimation from different uncontrolled median openings in India. We estimated the first input parameter required for Harders' formula, conflicting traffic volume, by analyzing the lateral placement of vehicles at the median opening area. We estimated the second parameter, critical gap, by using four different critical gap estimation procedures-namely; modified Raff, maximum likelihood, macroscopic probability equilibrium, and merging behavior. The third parameter, follow-up time, was measured directly in the field. Consequently, we calculated U-turn capacity for the given traffic streams and the findings were tested against the field capacity estimated in the field using Kyte's method. We then determined a suitable method for critical gap estimation in the Indian context by using two statistical parameters. � 2018 American Society of Civil Engineers.
Lateral placement of U-turns at median openings on six-lane divided urban roads
(2015) Mohapatra S.S.; Dey P.P.
Study on lateral placement of U-turning vehicle is carried out by collecting data at 13 different median openings of six-lane divided roads. It was found that the lateral placement of all the vehicles'' taking U-turn at median opening may be unimodal or bimodal. The unimodal distribution was described by normal distribution, whereas bimodal distribution was described separately by two different normal distributions; one for only 2-W'' and other for all the vehicles excluding 2-W.'' Equations were developed and parameters were calculated to describe a bimodal placement distribution curve. The issue of bimodality in placement was investigated statistically and the separation factor (S(r)) and placement factor (PF) were used to describe the issue. This study on the lateral placement of Uturning vehicles holds significance in the better estimation of conflicting traffic volume, which is essential for the correct estimation of the capacity of U-turns at median openings in mixed traffic condition. � 2015 Institute of Materials, Minerals and Mining.
Major Stream Delay under Limited Priority Conditions
(2019) Mohanty M.; Dey P.P.
Under a limited priority situation, U-turning vehicles attempt to accept smaller gaps, which compels approaching through vehicles to slow down and experience delays. Delay within the median opening area is termed median delay, which is studied in two parts: Median delay 1 (from start to center of median opening), and Median delay 2 (center to end of median opening). The significant difference between these two delays is established by a t-test. The effect of U-turning volume on Median delay 1, Median delay 2, and total median delay is studied. Considering the lateral movements of approaching through vehicles within the median opening area, the effect of the zone on median delay is studied. Furthermore, the effect of the category of U-turning vehicle on median delay is examined. Finally, three mathematical models are proposed considering the effect of (1) U-turning volume, (2) zone through which the vehicle is moving within the median opening area, and (3) category of U-turning vehicle. The proposed models are validated by comparing the model values with the field data. � 2018 American Society of Civil Engineers.
Merging process of u-turns at uncontrolled median openings under mixed traffic conditions
(2018) Sil G.; Mohapatra S.S.; Dey P.P.; Chandra S.
At an uncontrolled median opening, the limited priority situation and the high degree of heterogeneity in traffic stream make the merging manoeuvre of U-turning vehicles very much complex. This study is an attempt to understand this merging manoeuvre. The different types of merging manoeuvres have been identified in the field and accordingly classified into different categories. Depending upon the number of vehicles that can merge all together into the opposing through traffic by accepting a single gap, the merging has been classified into two types: single entry merging and multiple entry merging. On the other hand, based on the situation of priority of movement, the merging process is divided into another two categories: ideal merging and forced merging. More explicitly, the ideal merging is split into free merging and Swift Merging (SM). In addition, the forced entry merging is categorized into Gradual Merging (GM) and Aggressive Merging (AM). Time distance diagrams for different types of merging are presented for their better understanding. Field data collected at seven median openings located on various 6-lane divided urban roads are used to analyse different types of merging in a mixed traffic situation. All vehicles plying on the road are divided into 5 categories such as car, motorized two-wheeler (2-W), motorized three-wheeler (3-W), Sports Utility Vehicle (SUV), and Light Commercial Vehicle (LCV) and the merging behaviour of these categories of vehicles have been studied. The effect of influencing parameters like opposing traffic volume and delay on merging are investigated. Mathematical relations are developed between Merging Time (MT) of a vehicle type and the opposing traffic volume. To address the effect of Service Delay (SD) on the MT of a vehicle, models are proposed between SD and MT for all the five categories of vehicles. The two types of merging; gradual and swift are prominently observed in field. The time required by different categories of vehicles for these two merging at various traffic volume levels are determined. Finally, two-tailed t-test is conducted to see if the MT for the two different types of merging is statistically different. � 2016 Vilnius Gediminas Technical University (VGTU) Press.
Modeling the critical position of U-turning vehicles at uncontrolled median openings
(2016) Mohapatra S.S.; Dey P.P.; Chandra S.
The present study provides a methodology for identification of the conflict zone between a turning vehicle and on-coming vehicles at uncontrolled median openings on urban roads under mixed traffic conditions. Data for turning movements of different types of vehicles were collected at 13 median openings on 6-lane roads and 8 median openings on 4-lane roads in different cities of India. These data are analyzed statistically and it was found that the critical position (path of the outer wheel) of a vehicle is influenced by the vehicle size and the road width. In the case of 6-lane roads, the critical position of turning vehicle may follow a unimodal or bimodal distribution depending upon the proportion of motorized two-wheelers (2-W) in the turning volume. On 4-lane roads, the gamma distribution was found to fit the placement data at all the eight sections. A simple model is proposed to identify the boundary of the conflict zone at median openings. The geometrical augmentation required at the median opening in order to avoid the conflict between turning vehicles and through traffic in the opposing median lane is also suggested. � 2015, Korean Society of Civil Engineers and Springer-Verlag Berlin Heidelberg.
Modelling the area occupancy of major stream traffic
(2018) Mohanty M.; Dey P.P.
The U-turns at median openings interrupt the movement of approaching through vehicles. This results an overall reduction in speed and flow along with increase in density. It is difficult to measure density from field observations and it doesn't consider any heterogeneous characteristics of traffic stream. Alternatively, area occupancy takes into account the flow, speed, and the dimension of each vehicle. Therefore area occupancy is a much better measure to study the performance of a road as compared to traffic density. This concept assumes that the vehicles must move at a uniform speed while entering and exiting the test section which may be practically impossible to maintain for all the vehicles. Therefore, to overcome this assumption, a modified technique has been proposed in this study. Besides, the change in area occupancy at various segments of slow down section across different U-turning traffic volumes has been assessed. Finally, a regression equation has been modelled to estimate area occupancy at every segment of road section corresponding to any U-turning volume. This model has been validated by comparing the estimated values with the values obtained from field data and the MAPE is found to be less than 10%. � 2018 Institute for Transport Studies in the European Economic Integration. All right reserved.
Modelling the major stream delay due to U-turns
(2019) Mohanty M.; Dey P.P.
This study assesses the delay faced by approaching through vehicles at uncontrolled median openings due to U-turning movement. Under limited priority situation, the U-turning vehicles accept smaller gaps which compel the through vehicles to reduce their speeds and experience delays. First, the slowdown section is identified and the delay faced by through vehicles from the starting of slowdown section to start of median opening is estimated. This is termed as approach delay. The approaching vehicles shift laterally as they approach toward the median opening. The concept of zone has been introduced to study this lateral movement. This study shows that the vehicles moving through the zone adjacent to curb face more delay as compared to the vehicles moving through the zone adjacent to median. Finally, a regression model is developed for estimating approach delay faced by any vehicle category traveling through a particular zone at a given U-turning traffic volume. � 2017, � 2017 Informa UK Limited, trading as Taylor & Francis Group.
Performance of Lime Stabilization on Extremely Alkaline Red Mud Waste under Acidic Environment
(2019) Mishra M.C.; Sateesh Babu K.; Reddy N.G.; Dey P.P.; Hanumantha Rao B.
Excessive pH (>11) and inconsistent engineering properties because of the chemicomineralogical composition of red mud warrant devising an alternate approach to render it more environmentally benign. In this study, the performance of lime stabilization coupled with oxalic acid, which acts as a neutralizing agent, was explored systematically to improve the long-term strength and to reduce the alkalinity of red mud. The mechanisms governing the behavior of additives along with their effects were investigated by examining the mineralogical, elemental, and morphological characteristics. The results suggest an effect of sodalite and alumina on the inconsistency in dry unit weight and claylike behavior of red mud. A reduction in pH was found to be instrumental during early phases of lime stabilization and in precipitation of cementitious hydration products, leading to strength gain in the long term in red mud. Moreover, the addition of lime and oxalic acid was found to yield more encouraging results than lime treatment alone, and hence this is recommended to be used for red mud stabilization. The obtained results were substantiated by comparison with code provisions. � 2019 American Society of Civil Engineers.
Quantification of LOS at Uncontrolled Median Openings Using Area Occupancy Through Cluster Analysis
(2019) Mohanty M.; Dey P.P.
This study quantifies LOS ranges for traffic movement at uncontrolled median openings using �area occupancy� as a measure of effectiveness. The Highway Capacity Manual is silent about LOS ranges at uncontrolled median openings. Traditionally, traffic density is considered as an important parameter for quantifying the traffic flow. However, it does not consider the heterogeneous characteristics of the traffic stream. Further, occupancy also does not explain the heterogeneous traffic and the absence of lane discipline which is predominant in developing countries. Therefore, area occupancy is used in this study to assess the performance of traffic conditions at median openings. The established method to measure area occupancy has been modified to overcome the assumption used in earlier techniques. Area occupancy has been estimated for both major and minor traffic streams. K-mean clustering has been employed to classify area occupancy ranges for various LOS categories. This methodology could be beneficial for practitioner engineers to monitor the vehicular movement at median opening. � 2018, King Fahd University of Petroleum & Minerals.
Queue discharge characteristics at signalised intersections under mixed traffic conditions
(2013) Dey P.P.; Nandal S.; Kalyan R.
The evaluation of capacity at signalized intersection is an important component in the planning, design, operation and management of transportation system. Presently, the methodologies available for the estimation of capacity of signalised intersections are based on the concept of saturation flow (s). The study describes the headway, speed, and acceleration characteristics of vehicles during queue discharge after green onset under mixed traffic condition. For the present work data were collected at different signalized intersections in the city of Bhubaneswar, India under mixed traffic conditions. It has been found that the queue discharge headways shows an unmistakable pattern of gradual compression as queuing vehicles are discharged in succession. In this paper the speed at which the vehicles move during queue discharge for three different categories of vehicles (2-wheeler, 3-wheeler, and car) are also analysed. The acceleration characteristics of different category of vehicles released from stop after the green onset are also analysed in this paper and are explained by the non-uniform acceleration model in the form of (dv/dt) = ? - ?v. The average values of ? and ? for different category of vehicles are estimated.
Service delay and merging time evaluation at median openings
(2019) Sil G.; Mohapatra S.S.; Dey P.P.; Chandra S.
Studies have been carried out on delays at unsignalized intersections but there is hardly any report is available on delays at unsignalised median openings on multi-lane divided urban roads. The present study estimates the average service delay to vehicles and proposes service delay models based on microscopic analysis of delay data under highly heterogeneous and unruly traffic conditions. The data for the study were collected by video recording at seven different uncontrolled median openings on multi-lane divided urban roads in India. The conflicting traffic was measured as the exact number of conflicting vehicles (n) as seen by a particular U-turning vehicle. The number of conflicting vehicles and the opposing through traffic were found to affect the service delay and mathematical models have been proposed. The merging time was also estimated for different categories of vehicles. Furthermore, the effect of opposing traffic volume and delay on merging time is studied. � 2019 Institute for Transport Studies in the European Economic Integration. All rights reserved.