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Traffic safety at signalized intersections is significantly affected by the driver's behavior, psychology, and the design of traffic signals, especially in mixed traffic conditions. At signalized intersections, the traffic signal design influences the traffic behavior during the yellow change interval. The indecisiveness or the dilemma in decision-making during the yellow change interval often results in hard deceleration or red-light running, which concerns the safety of the road users in the form of rear-end and side-angled conflicts. Thus, it is essential to understand how traffic behavior and signal design changes affect safety. The present work investigates traffic behavior at signalized intersections operating under mixed traffic conditions using high-quality vehicular trajectory data obtained using unmanned aerial vehicles (UAVs). The analyzed traffic behavior is related to Type I and Type II dilemma zones at intersections with two types of traffic flow conditions: oversaturated and undersaturated. However, it is found that the position of these dilemma zones is near the stop line for an oversaturated intersection and away from the stop line for an undersaturated intersection, as it depends on the approach speeds of vehicles. The driver's decision-making behavior, which depends on the driver's psychology, is also analyzed, and a binary logistic regression model is developed for determining the Type II dilemma zone by considering various parameters at the onset of the yellow change interval. Further, the variation in the length of the Type I dilemma zone is studied by performing a sensitivity analysis and proposing measures for mitigating its negative effects. The findings underscore the critical importance of considering both traffic behavior and signal design in the safety analysis of signalized intersections, particularly in mixed traffic environments where driver behavior, psychology, and vehicle interactions are more unpredictable. Practical Applications: The findings from this study have significant practical applications for enhancing traffic safety at signalized intersections, especially in mixed traffic conditions like those in India. Utilizing high-quality trajectory data collected via UAVs, this research precisely identifies dilemma zones and comprehensively analyzes driver behavior during the yellow change interval. One key application is in optimizing traffic signal design and timing. By accurately locating Type I and Type II dilemma zones, traffic engineers can adjust signal timings and phase durations to minimize hard decelerations and red-light running, thereby reducing rear-end and side-angle collisions. The development of a binary logistic regression model for predicting Type II dilemma zones can be integrated into intelligent traffic management systems. This model allows for dynamic signal timing adjustments based on real-time traffic conditions, improving the adaptability and efficiency of traffic signals. Additionally, the proposed mitigation measures, such as adjusting the yellow change interval length and implementing speed control measures, can be directly applied by traffic authorities to enhance intersection safety, particularly in mixed traffic conditions. [ABSTRACT FROM AUTHOR]

This study is carried out to estimate the passenger car unit (PCU) values of different vehicle categories at a typical four-legged roundabout based on the concept of time occupancy. A stream equivalency factor (k) has also been developed based on the estimated PCU to convert the heterogeneous traffic flow into a homogenous stream equivalent without making use of PCU factors. Relationship between entry flow and circulatory flow has been plotted based on the observed data corresponding to the time period in which there was queue formation in the approach. Further, estimated critical gap and follow-up time have been used to derive the capacity by HCM 2010 equation. A multiplicative adjustment factor is suggested for the use of HCM 2010 equation directly in the field to estimate entry flow under heterogeneous traffic condition. The study results may be suitable for revising the code of practice, named IRC 65–1976, and useful for ongoing national-level efforts of developing Indian Highway Capacity Manual. [ABSTRACT FROM AUTHOR]

The present study focuses on modeling roundabout in heterogeneous condition and understanding the effect of change in two-wheeler composition on the entry capacity using microscopic simulation technique. A four-legged roundabout of 25m diameter, located in the city of Chandigarh, India was considered as the study area. As Indian traffic flow is highly heterogeneous due to the presence of vehicles with varying physical and operational characteristics, each vehicle modelled separately in PTV VISSIM. Model calibrations were performed using speed distributions, conflict areas, priority rules, and driving behavior parameters. Comparison with the field data obtained from the study roundabout (indicates the applicability of the developed simulation model in assessing the hypothetical scenarios. Study results indicate that the PCU values remain steady under varying compositions of two-wheelers in the traffic stream. In addition, the effect of two-wheeler proportion on roundabout capacity is insignificant in the study area. [ABSTRACT FROM AUTHOR]

Roundabouts have proven to be an effective intersection design method for smooth traffic flow movements and improved safety. Previous studies show that VISSIM, commercial traffic simulation software, can be used as a proficient tool for modeling and efficiently analyzing roundabouts. This paper focuses on developing a methodology for modeling roundabouts in India using VISSIM. Three typical roundabouts were chosen from the northern part of India. Calibration and validation of the model were performed to ensure the correctness of the model. The average delay and volume to capacity ratio (v/c ratio) were compared for developing the level of service (LOS) thresholds for Indian conditions. The thresholds are compared with existing guidelines provided by the HCM 2010 and AUSTROADS. In addition, the methodology for determining modification factors for applying HCM 2010 delay model in Indian traffic conditions is defined. [ABSTRACT FROM AUTHOR]

Pedestrian crossing activity at unmarked crosswalks on urban roads in developing countries like India is a common phenomenon. Pedestrians used to cross the road at their place of interest to access residential and commercial land use. Such crossing operations cause a twofold effect: first the pedestrian put themselves at high risk of collision with the moving traffic, and they also affect the normal traffic operations, which causes excessive delay to vehicular traffic. Available pedestrian crossing warrants (PCWs) based on PV2 (where P is the volume of crossing pedestrians per hour and Vis per-hourly traffic volume) focus on the safe movement of pedestrians, but traffic operation is least considered in such warrants. The present study deals with the development of pedestrian crossing facility warrants based on pedestrian safe movement along with vehicular delay, which includes traffic efficiency as well. The traffic data collected from four different locations through the videographic survey were used for evaluating the delay for the individual vehicle due to pedestrian crossing activity. The delay thus evaluated was further validated using the probe vehicle data collected during the same observation period. The vehicle was fitted with the GPS-based performance box instrument that provides the vehicle trajectory at any instance. A significant number of sample data were collected with the probe vehicle and delay was determined using trajectory data. The finding of the delay obtained from the field data was validated incorporating a simulation-based analysis to resemble the interaction of pedestrian flow dynamics with vehicular flows. The crossing behavior of pedestrians was simulated using microscopic simulation software VISSIM. The microsimulation model was first calibrated and validated for field traffic conditions. The total delay was assessed for the traffic stream, and it was found to follow a second-degree polynomial relationship with PV2 values. The clustering analysis was carried out using K-means clustering to define a threshold value for pedestrian crossing facilities. These warrants were also identified based on PV2 utilizing the relationship between total delay and PV2 values. The results of the present study will be useful for practicing engineers for designing pedestrian crossing facilities considering pedestrian safety and vehicular operation as well. [ABSTRACT FROM AUTHOR]

Traffic characteristics of a roadway are significantly influenced by bus stops, and it becomes more chaotic when a separate bus bay is not provided and the bus has to be stopped in the curb lane. The present study analyzes the effect of such bus stops on the midblock capacity of urban arterials under heterogeneous traffic conditions. Field data have been collected at six sections of six-lane divided urban arterial roads; out of that, three sections have not marked with bus stop and referred to as base sections, whereas the other three have designated bus stops and denoted as friction sections. A set of simultaneous equations are established using speed and flow data to estimate the midblock capacity of urban roads and found to be 6000 PCU/h for one direction of flow. Further, a set of simultaneous equations are developed between the speed of a vehicle type and the densities of all categories of vehicles with densities of stopped buses in their individual terms. These equations are solved for any number of stopping buses at a fixed proportion of vehicles in the traffic stream for different traffic volume levels and thus get the capacity curves. It has been found that the capacity of urban arterials is reduced by 6.6–28.3% when the frequency of stopping buses is as low as 20 bus/h to as high as 120 bus/h, respectively. The study outcomes are useful for designing bus stops and at the same time estimating the capacity of such sections in order to reduce the congestion on the urban roadway network. [ABSTRACT FROM AUTHOR]

This paper presents a vehicle-type-specific headway distribution analysis at toll plazas under mixed traffic conditions. The aim of the paper is to provide headway distribution models that may be used for traffic flow analysis and traffic management at tollbooths. Seven classes of vehicle and a total of 49 combinations of leader–follower vehicles were considered, out of which 11 combinations were considered for studying the headway distribution model based on the frequency of arrival of such vehicle combinations at tollbooths. The results showed that vehicle classes requiring a headway of 5–25 s followed a log-normal distribution whereas, for higher headway ranges of 15–40 s, the generalised extreme value showed the best fit. For the small car category, the Wakeby distribution showed a better result than conventional distributions. The findings of this study may be useful for developing toll plaza microscopic simulation models, which could be used for assessing and improving the performance and efficiency of tollbooths. [ABSTRACT FROM AUTHOR]

Pedestrian crossing at midblock sections of urban roads at undesignated places is a normal phenomenon in developing countries. These locations are undesignated places, i.e., not marked with any zebra crossing, pedestrians' signals or grade-separated facility. Still the Pedestrians cross the road to access their desired place in order to save time which negatively affects traffic movement. The present study attempted to quantify the reduction in capacity of 6-lane and 4-lane divided urban arterial roads due to such crossing maneuver by pedestrians. Capacity of base section, i.e., section does not have pedestrian cross-flow or any other factors influencing traffic flow, is determined from field data. These capacity values are compared with the capacity of section under the influence of pedestrian crossing. Data were collected on twenty-two different locations of 4-lane and 6-lane urban arterials in five different metropolitan cities. The speed–volume data are extracted from field data in order to find out the capacity of base sections and friction sections. The mathematical equation has been developed showing the relationship among pedestrian cross-flow and capacity drop. It has been found that there is no impact on capacity when pedestrian cross-flow is limited to 200 pph (pedestrians/hour). However, the capacity reduces by 32% when pedestrian cross-flow is raised to 1550 pph. Further, the safe pedestrian crossing facilities are recommended based on pedestrian and vehicular volume analysis. [ABSTRACT FROM AUTHOR]

Mixed traffic flow is often converted to equivalent flow in passenger car units (PCUs) by multiplying the number of each category of vehicles in the traffic stream by their respective PCU factors and then adding them up. PCU is a complex parameter and depends on multitude of factors. This paper presents a methodology to convert a mixed traffic stream into a homogeneous equivalent without making use of PCU factors. Traffic volume and speed data collected on different six-lane urban arterial roads in India are analyzed to determine PCU values of five different categories of vehicles found on these roads. These PCU values are used to convert heterogeneous traffic volume in vehicles per hour to homogeneous volume in PCU per hour. A new term stream equivalency factor (SEF) is introduced in this study and denoted by . It is the ratio of traffic volume in PCU per hour and volume in vehicles per hour. The factor is related to traffic composition and volume on a road through the regression analysis method. A microsimulation program is used to generate the traffic flow data for two, three, four, and five categories of vehicles in the traffic stream, and these data were utilized to present a generalized solution for determining the value of for any combination of traffic composition and volume on a road. The proposed method is simple to use and expected to eliminate the problem of estimation of PCU factors required in many studies. [ABSTRACT FROM AUTHOR]

Most projects across the world are built under the public--private partnership (PPP) module. In the highway sector, the highway projects are built by the concessioner, and in lieu of that, he generates revenue by collecting tolls from road users. The toll plazas built across the highways to collect tolls act as a bottleneck in highway facilities. Although the toll collection system has been improved worldwide, users are still experiencing an enormous delay at toll plazas due to congestion, especially in developing countries like India. This congestion is caused due to various factors such as long service time, an inadequate number of windows, traffic volume, categories of toll rates, etc., which lead to delay, degradation of capacity, and level of service. Different researchers in their countries have analysed all these factors. The present article gives a detailed literature review summarizing various studies on the different parameters related to toll plazas and proposes research gaps from the perspective of developing countries. The challenges and methodology for evaluating various parameters are also discussed, and a way forward for future research is suggested. [ABSTRACT FROM AUTHOR]