Satish Chandra

Bio: Satish Chandra is an academic researcher from Council of Scientific and Industrial Research. The author has contributed to research in topics: Traffic flow & Level of service. The author has an hindex of 27, co-authored 142 publications receiving 2329 citations. Previous affiliations of Satish Chandra include Council for Scientific and Industrial Research & Indian Institutes of Technology.

Effect of lane width on capacity under mixed traffic conditions in india

Abstract: A new concept to estimate the passenger car unit (PCU) of different types of vehicles under mixed traffic conditions is presented. It utilizes the area, as opposed to only the length, and speed of a vehicle. Data were collected at ten sections of two-lane roads in different parts of India. The width of carriageway (this term is commonly used in India for the total width of the paved surface of a road excluding its shoulders) ranged from 5.5 to 8.8 m. All vehicles were divided into nine different categories and their PCU's were estimated at each road section. It was found that the PCU for a vehicle type increases linearly with the width of carriageway. This is attributed to the greater freedom of movement on wider roads and therefore a greater speed differential between a car and a vehicle type. The capacity of a two-lane road also increases with total width of the carriageway and the relationship between the two follows a second-degree curve. This relationship is used to derive the adjustment factors for substandard lane widths and the results are compared with literature.

Pedestrian Flow Characteristics in Mixed Traffic Conditions

Abstract: Data collected at four locations in a medium-sized city of India are analyzed for pedestrians flow characteristics under mixed traffic conditions. The data are presented in the form of mathematical and graphical relationships between speed and volume, speed and density, flow and area module, and flow and density. The results of analysis are compared with those given in literature. The free-flow speed of pedestrians is observed to be 80 m/min which is higher than that reported for China and Singapore, but slightly lower than that in Germany. It is comparable to free speeds reported for Philippines and the United States. The speed of the pedestrian was found to be influenced by the age and gender also. Male pedestrians move faster than female pedestrians. Pedestrians in the age group of 10–15 years had the highest speed, 82 m/min. the speed was reduced by about 85% when pedestrians move with their baggage (or luggage).

Speed Distribution Curves under Mixed Traffic Conditions

Abstract: Most of the studies available in the literature indicate that the speed data on a highway follow the normal distribution. The present study indicates that the speed distribution may be a unimodal or a bimodal curve depending upon the variation in the speed of different categories of vehicles moving on the highway. The mathematical equations are suggested for unimodal and bimodal speed distribution curves, and their parameters are evaluated at 17 different sections of two-lane roads in India. It is observed that the proportion of slow moving vehicles is not a true indicator of bimodality in the speed data. The spread ratio defined as the ratio of the difference between 85th percentile and mean stream speed to the difference in mean stream speed and 15th percentile speed, is better correlated with the shape of the speed distribution curve. The speed data follow the unimodal curve only when the spread ratio is in the range of 0.69–1.35.

Critical gap through clearing behavior of drivers at unsignalised intersections

Abstract: Critical gap is an engineering concept generally used for determination of capacity of individual movements at unsignalised intersections. Majority of studies on critical gap estimation are reported from homogeneous traffic conditions where lane discipline and the rule of priority are truly respected. Vehicular interactions and drivers’ behavior at unsignalised intersections under mixed traffic are very complex. In this study critical gap is estimated by some of the existing methods like lag, Harder, logit, probit, modified Raff and Hewitt methods, at two T-intersections located in the southern part of India. The results show that values of critical gap estimated are as low as 1.60 s and there is a significant variation (12%–38%) among the values estimated by different methods. This highlights the incapability of the existing methods to address the mixed traffic conditions. An alternate procedure of estimation of critical gap making use of clearing behavior of vehicles in conjunction with gap acceptance data is proposed. Incorporating clearing time aspect gives more realistic estimation of critical gap and helps in accurately estimating the entry capacity.

Do transportation network companies decrease or increase congestion

Abstract: This research examines whether transportation network companies (TNCs), such as Uber and Lyft, live up to their stated vision of reducing congestion in major cities. Existing research has produced conflicting results and has been hampered by a lack of data. Using data scraped from the application programming interfaces of two TNCs, combined with observed travel time data, we find that contrary to their vision, TNCs are the biggest contributor to growing traffic congestion in San Francisco. Between 2010 and 2016, weekday vehicle hours of delay increased by 62% compared to 22% in a counterfactual 2016 scenario without TNCs. The findings provide insight into expected changes in major cities as TNCs continue to grow, informing decisions about how to integrate TNCs into the existing transportation system.

Characterization of Cementitiously Stabilized Layers for Use in Pavement Design and Analysis

Abstract: This report presents information on the characterization of cementitiously stabilized layers and the properties that influence pavement performance. It also contains recommended performance-related procedures for characterizing these layers and performance-prediction models for incorporation into the mechanistic–empirical pavement analysis methods. Individual chapters highlight pavement distresses of hot-mix asphalt pavements and concrete pavements, laboratory tests and model development, and model calibration. The material contained in the report will be of immediate interest to state materials, pavement, and construction engineers and others involved in the different aspects of pavement design and construction.

Reachability Analysis and its Application to the Safety Assessment of Autonomous Cars

Abstract: This thesis is about the safety verification of dynamical systems using reachability analysis. Novel solutions have been developed for classical reachability analysis, stochastic reachability analysis, and their application to the safety assessment of autonomous cars. Classical reachability analysis computes the set of states that can be reached by a system. If the reachable set does not intersect any set of unsafe states, the safety of the system is guaranteed. Algorithms for this problem have been developed for linear, nonlinear, and hybrid systems. Stochastic reachability analysis measures the probability of reaching an unsafe set. One pursued approach computes over-approximative solutions for linear systems; another one generates a Markov chain which approximately computes the stochastic reachable set of arbitrary dynamics.