Modeling Adjustment Factor of Saturation Flow Rate for the Exit Lanes for Left-Turn Control
Jing Zhao, University of Shanghai for Science and TechnologyShow Abstract
Yue Liu, University of Wisconsin, Milwaukee
Xizhao Zhou, University of Shanghai for Science and Technology
As a newly proposed unconventional intersection design, the exit lanes for left turn (EFL) intersections have promising benefits in increasing capacity of the entire intersection. However, whether the saturation flow rate of the left-turn lanes is the same as that of conventional intersections, and the influence factors thereof, remain unknown. In this paper, a saturation flow rate adjustment model for EFL control is proposed based on field data. Five influencing factors, namely the median opening blockage, demand starvation, multi-lane interference, conflict with opposing vehicles, and lane changing are considered. The accuracy of the model is validated using nonparametric tests. The results show that the reduction in saturation flow rate for the normal approach left-turn lanes, the left-turn lanes in the mixed-usage-area, and the left-turn lane at the pre-stop line caused by EFL control are 6%, 31%, and 19%, respectively. The main impact factors for the saturation flow rate at the main-stop line and the pre-stop line are the demand starvation (16% reduction) and lane changing (16% reduction), respectively. More guiding signs and markings and adequate signal timings assist in increasing the saturation flow rate of the left-turn lanes at the EFL intersections.
Cycle-by-Cycle Maximum Queue Length Estimation at Signalized Intersections in Connected-Vehicle Environment
Han Zhang, Beihang UniversityShow Abstract
Henry Liu, University of Michigan, Ann Arbor
Peng Chen, Beihang University
Guizhen Yu, Beihang University
Yunpeng Wang, Beihang University
Queue length is a crucial measurement of intersection performance. With the improvements of connected vehicle (CV) technology, using data collected from CVs to estimate queue length has received considerable attention from numerous researchers. It is worthy of noting that most of the existing studies require higher penetration rates of CVs, e.g., 25%, to ensure the estimation accuracy. Though the penetration rate of CVs is expected to increase, it is still relatively low in the near future. Thus, this study proposes a cycle-by-cycle maximum queue length estimation method using CV trajectories under relatively lower penetration rates. The proposed approach consists of two major steps. First, vehicle arrival process is modeled as a Poisson process and an Expectation Maximum (EM) procedure is employed to estimate the arrival rate of each cycle. Then, maximum queue length of each cycle is estimated based on the shockwave theory. Last, a real-world intersection is modeled in the microscopic simulator VISSIM to examine the performance of the proposed approach under different penetration rates. The results demonstrate that the proposed approach can estimate cycle-by-cycle maximum queue length with desirable accuracy even under a relatively lower penetration rate, e.g., 10%. The remaining limitations of the methodology are also discussed in this paper.
Multimodal Level-of-Service Methodologies: Arterial Corridors’ Multimodal Assessment
Natalia Zuniga Garcia, University of Texas, AustinShow Abstract
Randy Machemehl, University of Texas, Austin
Heidi Ross, University of Texas, Austin
The principal objective of this research is to evaluate the multimodal performance of arterial corridors using currently available MMLOS methodologies. Eight different Multimodal Performance Level of Service approaches are applied to a case study using an arterial corridor section in Austin, Texas. The methods applied are (1) Highway Capacity Manual, (2) Transit Capacity and Quality of Service, (3) Charlotte’s Urban Streets Design Guide, (4) Pedestrian and Bicycle Environmental Quality Index, (5) Level of Traffic Stress, (6) Bicycle Compatibility Index, (7) Deficiency Index, and (8) Walk Score®, Bike Score®, and Transit Score®. The analysis is focused on the pedestrian, bicycle, and transit assessment. The methodologies are evaluated and contrasted. The paper provides a compressive review of the current state of practice of multimodal evaluation, and recommendations about the most appropriate approaches to assess multimodal performance of arterial corridors.
Total Capacity of Roundabouts: Analyzed by Conflict Technique
Werner Brilon, Ruhr University, BochumShow Abstract
Ning Wu, Ruhr University, Bochum
The conventional way of capacity analysis is based on the critical gap method or on empirical regression or a combination of both. Influence of pedestrians is modeled by reduction factors with a rather questionable empirical background. Thus, the current methods are based on an incoherent mix of sophistications. Moreover, they do not account for the interaction between the different elements.
The paper presents a new model, which treats the whole intersection as one entity. Here all the conflicts where different streams (vehicles and non-motorized road users) intersect within the roundabout are identified. Each conflict point is treated as one queuing system with a simplified queuing mechanism. In addition, the interactions between the consecutive queuing systems at roundabouts are taken into account according to the theory of chains of queues where the distance (= storage area) between the conflict points becomes important.
The paper explains the sophistication of the model, presents the mathematical derivations of ready-to-use capacity equations plus parameter calibration by existing data, and demonstrates real-world application. The advantages of the technique are: all conflicts - both between vehicle streams and pedestrian conflicts at entries and exits - are treated by the same congruent methods. Also the interaction between consecutive arms of the roundabout is modeled. By the technique it becomes also possible to model limited priorities (e.g. for pedestrians at crosswalks or zebra crossings) for all conflict points. Finally, the conflicts which are decisive for the performance of the whole intersection are identified. The methods can easily be implemented into relevant computer software.
Estimation of Standard Pedestrian Equivalent Factors for Heterogeneous Pedestrian Stream Containing Individuals with Disabilities
Sohrab Mamdoohi, Utah State UniversityShow Abstract
Ziqi Song, Utah State University
Mohammad Sadra Sharifi, Utah State University
Hossein Nasr-Isfahani, Utah State University
Pedestrian flow, similar to vehicular traffic, can be considered as a heterogeneous flow. Presence of different types of individuals, including individuals with and without disabilities, shapes this heterogeneity in pedestrian stream. Dealing with diversity issue in pedestrian stream, a passenger car equivalent (PCE) type factor can be estimated to convert the heterogeneous flow into an equivalent individual without disability. In order to do that, a new concept of equivalent factor is introduced in this paper. The methodology employed in this paper is derived from vehicle PCE methodologies. Data used in this study is from a large-scale controlled walking experiment involving individuals with disabilities conducted at Utah State University (USU). Pedestrian walking behaviors in two walking facilities (a passageway and a bottleneck) are studied in unidirectional stream. The purpose of this study is to introduce an approach to consider heterogeneity in pedestrian flow by obtaining a better understanding of pedestrians’ walking behaviors. The finding of this study might be useful to develop pedestrian simulation models. Results reveal that the visually impaired individuals walk more conservatively due to their decreased ability to see. Moreover, analysis indicates that pedestrian stream is more uniform in bottleneck compare to the passageway.
Evaluation of the Roundabout Capacity Model in HCM 6th Edition and HCM 2010 on a Multilane Roundabout
Rongsheng Chen, University of Minnesota, Twin CitiesShow Abstract
John Hourdos, University of Minnesota, Twin Cities
This study evaluated the accuracy of the new Highway Capacity Manual 6 th Edition (HCM6) roundabout capacity model using data from a multilane roundabout in Richfield, Minnesota. Traffic flow rates and gap acceptance data were collected during 20 hours of afternoon peak period traffic over four days. The observed critical headways for the left and right lanes equaled to 4.43 and 3.99 seconds while the observed follow-up headways were 3.05 and 2.96 seconds respectively. Roundabout capacity curves for each lane where fitted both through the collected flow information as well as through the observed headways and the HCM6 formula.
As compared to the field observed results, the default model in HCM6 overestimated the capacity of the study roundabout. The default model in HCM 2010 closely estimated the capacity for the right lane, but significantly overestimated the capacity of the left lane when the circulating flow rate was high. The HCM6 model was calibrated by using the critical headway and the follow-up headway observed, as well as by calibrating the intercept of the model using only the follow-up headway. The first calibrated model overestimated the capacities of the right lane by 7% to 10% as the circulating flow decreases while the difference on the left lane ranged between 7% and 31% similarly. The second calibrated model overestimated the capacity of the left lane by 6% and underestimated the capacity of the right lane by 5%.
Modeling the Impacts of Heavy Vehicle and Geometry on Roundabout Entry Capacity
Yujia Zhao, Nagoya UniversityShow Abstract
Xin Zhang, Nagoya University
Wael Alhajyaseen, Qatar University
Hideki Nakamura, Nagoya University
Entry capacity is one of the most important indices used to predict roundabout operational performance and its ability to accommodate the expected traffic demand. Existing procedures, such as the proposed ones by Highway Capacity Manual HCM (2016) and the Japan Roundabout Manual JRM (2016), estimate entry capacity using the gap acceptance theory by defining fixed values for the gap parameters in circulating and entry flows without considering the impact of roundabout geometry. In reality, roundabouts are being constructed with different layouts, which may leave significant impacts on driver behavior and the achieved entry capacities. This study aims at analyzing the impacts of roundabout geometry and heavy vehicles on the gap parameters as well as the estimated entry capacity. Empirical data are collected by video surveys at eight roundabouts in Japan. Then using image-processing software, gap parameters are extracted from video records. The empirical analysis verified the significant influence of geometric elements on gap parameters and entry capacity. The developed methodology for the estimation of entry capacity can reliably quantify the impact of heavy vehicle ratios in the entry approach and the circulatory roadway as well as roundabout geometric layout.
Modeling the Impacts of Traffic Flow Arrival Profiles on Ramp Metering Queues
Guangchuan Yang, University of Nevada, RenoShow Abstract
Rui Yue, University of Nevada, Reno
Tian Zong, University of Nevada, Reno
Hao Xu, University of Nevada, Reno
An adequate queue storage length is critical for a metered on-ramp to prevent ramp queue spillback to the upstream signalized intersection. However, none the existing ramp meter design guidelines take into account the potential impacts of various on-ramp traffic flow arrival profiles on ramp queue lengths. This paper studies the traffic flow arrival profiles and queue generation processes at three different metered on-ramp categories. Based on large number of microscopic simulation runs, it is found that under a given demand-to-capacity scenario, queue at a metered on-ramp with two on-ramp feeding movements is more likely to be cleared in a cycle in comparison with at a metered on-ramp with three on-ramp feeding movements. Also, the platoon dispersion effect significantly reduces the ramp queue length, and hence the queue storage needs at a metered on-ramp. In addition, this paper reveals that the upstream signal timing setting affects ramp queue length; a longer upstream signal cycle length tends to produce a longer ramp queue. In these regards, the design of queue storage length for a metered on-ramp needs to fully consider the various ramp configurations and upstream signal timing settings.
Effect of Traffic Composition on Capacity of Six-Lane Urban Arterial Midblock Sections
Rajendra Meena, Sardar Vallabhbhai National Institute of Technology, SuratShow Abstract
Ashish Dhamaniya, Sardar Vallabhbhai National Institute of Technology, Surat
Satish Chandra, Central Road Research Institue-CSIR
Traffic is heterogeneous in all countries in the world including US but the degree of heterogeneity is different in developing and developed countries. The Highway capacity manual (HCM 2010) of US has defined two categories of vehicles visually car and heavy vehicles. However, in the car category there are many models like hatchback, sedan, SUV and XUV are plying on the road whereas in the heavy vehicle category, bus, two and three axle trucks are there on the roads. The operating and physical characteristics of these vehicles are different and they affect the speed flow characteristics of the stream at different flow levels thus consequently affect the capacity of the roadway. The present paper demonstrates the effect of traffic mix on the capacity of urban arterial roads and proposes a mathematical model to determine the capacity of six-lane divided urban arterial at varying compositions of vehicles present in the traffic stream. Microscopic simulation software VISSIM is used to develop the model. Speed flow characteristics of various categories of vehicles are studied in the field and are used to calibrate and validate the model for mixed traffic conditions. Traffic data collected in the field are used to derive capacity of the road in terms of equivalent passenger car unit (PCU) per hour. The capacity of six-lane road as achieved from the field data is 6300 PCU/hr for one direction of traffic flow. This capacity value was further achieved through simulation run for ‘all car’ conditions using calibrated VISSIM software. The program was run for small car and one of the remaining four categories of vehicles at different compositions in the traffic stream. Regression equations were developed for each set of simulation run for all four categories of vehicle along with the standard car. These equations are then combined to develop the capacity model. Further, a stream equivalency factor (SEF) is developed that can be used to convert heterogeneous traffic stream into homogeneous equivalent without actually using the passenger car units (PCU) values. The proportion of each category of vehicle in the traffic mix and the total traffic volume (in veh/hr) are taken as independent variables in developing SEF model.
Two models have been proposed in the study. The capacity model may be used for quick estimation of volume to capacity (v/c) ratio which is a surrogate measure of level of service (LOS) on the roadway. At the same time, the capacity of a roadway can be determined in pcu/hr using SEF model without actually using the PCU factors. Similar models can be formulated in developed country’s context where a variety of vehicles is present in the traffic stream.
Estimating Queue Length for the Contraflow Left-Turn Lane Design at Signalized Intersections
Jiaming Wu, Southeast UniversityShow Abstract
Pan Liu, Southeast University
Huaguo Zhou, Auburn University
Jie Bao, Southeast University
An unconventional left-turn treatment entitled the contraflow left-turn lane (CLL) design has been increasingly used in China to relieve the traffic congestion associated with the left-turn movements at signalized intersections. Field data collection was conducted on six approaches at five signalized intersections in the city of Handan, China, and a total of 40 hours of traffic data were recorded. A binary logit model was developed to estimate the probability of a driver stopping at the pre-signal when there are still vacant spaces in the conventional left-turn lane between the main and pre-signals. A modified shock-wave based method was then proposed for estimating the maximum queue length for the signalized intersections with the CLL design by considering the unique queuing behavior at the pre-signal. Sensitivity analyses were conducted to identify the impacts of the key parameters in the proposed queue length model on the maximum queue length of left-turning vehicles. The results suggest that the effective red time duration, the offset between the main and pre-signals and the queuing behavior of left-turning vehicles at pre-signals greatly affect the maximum queue length. The proposed queue length model was validated against the field data considering varying left-turn traffic demands. The mean absolute percent error (MAPE) generated by the proposed queue length model varies from 3.1% to 28.6% with a mean of 14.03% at the selected sites, indicating that the proposed model provides reasonable estimates for the maximum left-turn queue length at the signalized intersections with the CLL design. With the proposed procedure, the guidelines regarding the geometric requirements for implementing the CLL design were provided.
Speed Prediction Model on Four-Lane Urban Arterials Under Mixed Traffic Conditions by Using Simultaneous Equation Approach
Ashish Dhamaniya, Sardar Vallabhbhai National Institute of Technology, SuratShow Abstract
Satish Chandra, Central Road Research Institue-CSIR
Speed is a fundamental measure of traffic performance of a roadway system. It indicates the quality of service experienced by the traffic stream and it depends on traffic volume or density on the road. In a mixed traffic situation, congestion (or pavement occupancy) on a section will depend upon the number of vehicles of different categories in the traffic stream. For the same value of traffic volume, a vehicle may experience different congestion levels depending upon the proportional share of large size vehicles like heavy vehicles and small size vehicles like motorized two-wheelers. Hence the speed of a vehicle type will depend upon the total density on the road and this total density comprises of densities of individual vehicle types. In the present study field data were collected on different sections of four-lane urban arterials in New Delhi, Jaipur and Chandigarh by video recording method. The speed flow data collected from field shows the parabolic relationship between flow and speed that reproduce the linear speed-density relationship. The present study extends this linear speed-density relation to mixed traffic condition and attempts to develop a set of simultaneous equations relating speed of a vehicle type to the densities of all categories of vehicles in their individual terms. These equations are solved for some assumed values of traffic volume and traffic composition and effect on speed of each vehicle type is explained. It has been observed that there is a gentle reduction in speed of two wheelers from low flow level to the capacity level of flow whereas at the same time reduction in speed of heavy vehicles is steeper for the same flow range. It has been explained on the basis of vehicle maneuverability. Two wheelers are small in their physical size and because of better maneuverability as compared to the heavy vehicles can able to maintain the speed at high flow level. The degree of damaging effect on speed of heavy vehicle at the same time is high because of poor maneuverability. Accuracy of the equations is checked by comparing the observed values of speed with calculated speeds from simultaneous equations.
Roundabout Capacity in Heterogeneous Traffic Condition: Modification of HCM Equation and Calibration
Asir Khan, UCOE, Kaman, MumbaiShow Abstract
Sonu Mathew, University of North Carolina, Charlotte
Ashish Dhamaniya, Sardar Vallabhbhai National Institute of Technology, Surat
Shriniwas Arkatkar, Sardar Vallabhbhai National Institute of Technology, Surat
Joshi Gaurang, Sardar Vallabhbhai National Institute of Technology, Surat
The highway capacity manual (HCM-2010) is widely referred document around the globe for planning and design of roads. However, the transferability of HCM recommendations for heterogenous traffic condition represents a major research issue as they are often not suitable to properly explain the traffic complexities of a mixed-traffic condition. 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 concept of time occupancy. Also, this research investigates the suitablility of HCM equations for determining the entry capacity of a four-legged roundabout under mixed traffic condition and proposes a methodology for validating and calibrating HCM equations for performance evaluation. Data corresponding to traffic composition, traffic volume, critical gap and follow-up time have been extracted from video records collected at four roundabouts. Relationship between entry flow and circulatory flow has been plotted from the observed data when there is a complete saturation in the approach leg and depicted that it follows a negative exponential behavior. It implies that the entry capacity reduces exponentially with increase in circulating flow. Critical gap has been estimated by Maximum Likelihood Method (MLM). Further, a stream equivalent critical gap and follow-up time have been derived due to the mixed traffic scenario at the study location. A multiplicative adjustment factor of 1.1 is suggested for the use of HCM 2010 equation directly to estimate entry capacity under heterogeneous traffic condition. The study results may use for planning and designing of roundabout under mixed-traffic flow.
Investigating Entry Capacity Models of Roundabouts Under Heterogeneous Traffic Conditions
Ashish Patnaik, National Institute of Technology, RourkelaShow Abstract
Ankit Raj Ranjan, National Institute of Technology, Rourkela
Prasanta Bhuyan, National Institute of Technology, Rourkela
The primary objectives of this study are to develop the two roundabout entry capacity models by utilizing regression based MNLR model and artificial intelligence based ANFIS model under heterogeneous traffic conditions. Required data have been collected from 27 roundabouts spanning across 8 states of India. To assess the significance of these models and select the best model among them modified rank index (MRI) is applied in this study. The coefficient of determination (R2) and Nash–Sutcliffe model efficiency coefficient ‘E’ values are found to be (0.92, 0.91) & (0.98, 0.98) of MNLR & ANFIS model respectively. ANFIS model is found to be the best model in this study. But in a practical point of view, MNLR model is recommended for determining roundabout entry capacity under heterogeneous traffic conditions. Sensitivity analysis reports that critical gap is the prime variable and sharing (18.43 %)for the development of roundabout entry capacity. As compared to Girabase formula (France), Brilon wu formula (Germany) & HCM 2010 models, the proposed MNLR model is quite reliable under low to medium range of traffic volumes.
Evaluation of the Service Level of a Highway Toll Plaza in Brazil Using Computational Simulation
Patricia Pereira Arantes Inacio, UNIFEIShow Abstract
Fabiano Leal, Federal University of Itajuba
Josiane Lima, Federal University of Itajuba
The capacity and service level of highway tolls plazas is directly related to the service time at each toll booth, which depend on operational and human factors; in turn, these aspects influence and help strategic decision-making processes related to toll plaza management. Therefore, this study aims to assess the offered service levels at a Brazilian highway toll plaza, using computational modeling and simulation, and testing the influence of factors over manual customer service. Data collection offered information about the vehicle categories, the payment forms, work shifts, hours of the day and sex of the toll booth operator. It was also possible to collect information about the total number of vehicles, which went through each tool booth and break this information down into its composition. It can be concluded that the service level offered by the toll plaza on normal days is D, in which the vehicles remain in the system (waiting in line, plus processing time at booth) between 45 and 60 seconds. Other important information was extracted from the study upon which may serve as a basis for decision-making related to service, quality, traveling and driver safety provisions, aside from improving the operational system used by the toll road operator.
Understanding Traffic Flow Characteristics and Capacity of Linear Multiwork Zones on the Urban Arterial Road
Yadan Yan, Zhengzhou UniversityShow Abstract
Xiaobo Qu, University of Technology, Sydney
Miaomiao Zhu, Zhengzhou University
It is quite common that several construction projects are implemented synchronously on the urban arterial roads of many large cities in China. Unfortunately, despite the popularity and prevalence of these multi-work zones, there does not exist any technical/design standards for this type of work zones. In this paper, based upon the spatial relationships, we define linear multi-work zones as work zones that are arranged along the longitudinal direction of an urban arterial road. Traffic operation and capacity of linear multi-work zones are analyzed and discussed. By taking advantage of traffic data from the linear multi-work zones with intersections in Zhengzhou city, the impact of traffic operational characteristics including traffic volume, travel speed and vehicle headway is examined. We further develop a speed-flow relationship model for linear multi-work zones with intersections. The model suggests that difference in length between work zones and distance from intersections are two important factors affecting the travel speed and traffic flow. As for linear multi-work zones without intersections, VISSIM simulation is utilized. The simulation results indicate that distance between work zones and speed distribution greatly impact the total capacity.
Impact Assessment of Short-Term Work Zones on Intersection Capacity in New York City
Nawaf Alshabibi, University of DammamShow Abstract
Elena Prassas, New York University
New York City infrastructure is one of the oldest transportation infrastructures in the United States. Local street construction and short-term work zones are almost continuously planned events that affect the movement of traffic on city streets by requiring the closing of one or more lanes at intersections throughout NYC, and it is important to understand the effect on capacity due to such work.
This paper looks at the effect of short-term work zones on the capacity of signalized intersections in New York City. Data was collected at five locations in New York City, both during the work zone and then again after the work zone was removed. Over 25 hours of video data was collected and reduced. It was found that at all locations, the saturation headway was smaller during the work zone compared to after the work zone was removed, that is, the saturation flow rate per lane increased during the work zone. This was an unexpected result. A possible reason for this is the increased traffic pressure that drivers feel when a lane is closed. Thus, although overall approach capacity does decrease because a lane is closed, it did not decrease as much as expected. The field values are then compared with those from two other models: the HCM  model and a model developed by Schroeder et al. . It was found that both models underestimate the capacity of the approach.
Discharge Characteristics Analysis of Queue-Up Vehicles at Signal-Controlled Intersections
Satyajit Mondal, Indian Institute of TechnologyShow Abstract
Ankit Gupta, Indian Institute of Technology (BHU) Varanasi
Characteristics of discharge vehicle play a significant role in the concept of capacity estimation and designing of a signal controlled intersection. HCM (2000) presents a methodology for analyzing signalized intersection considering details of each parameter for a lane based car dominated traffic stream, with limited applicability for the mixed traffic conditions. The present study analyses the departure headway characteristics of queued vehicles where a decreasing trend is observed with increase in vehicle position with a saturation headway of 2.05 sec/veh. The distributions of departure headways are also analyzed, and hypothesis result shows that the departure headways at each vehicle position follow a particular log-normal distribution with varying mean and variance. An optimization technique is framed to find out the discharge of vehicles through minimizing the difference between observed flow and ideal flow proposed by HCM 2000. Dynamic PCUs are also estimated through minimizing the Theil's coefficient for accurate estimation of discharge pattern for mixed traffic conditions. The result shows that optimized discharge pattern is close to the ideal one with maximum saturation flow of 1908 PCUs/hr (HCM proposed 1900 PCUs/hr). A comparative analysis is done between the obtained flow value and flow value proposed by several guidelines and studies to check its suitability for mixed traffic stream.
An Approach for Estimation of Passenger Car Unit Values of Vehicles Based on Influence of Neighboring Vehicles
Pooja Raj, National Institute of Technology, KarnatakaShow Abstract
Shahana A, National Institute of Technology, Karnataka
Gowri Asaithambi, National Institute of Technology, Karnataka
Ravi Shankar A U, National Institute of Technology, Karnataka
Estimation of Passenger Car Unit (PCU) values is important for traffic capacity analysis, level of service measures, signal design and coordination, saturation flow rate determination and development of traffic flow models. Due to these wide applications, accuracy of PCU values is considered to have significant influence on traffic flow analyses. In developed countries, various methods were devised for estimating PCU values. But these methods are not completely applicable for mixed traffic because of the presence of wide variety of vehicle types, non-lane discipline and intra-class variability of vehicles. Moreover, limited studies considered the influence of neighboring vehicles to determine PCU values. Hence, this study aims to estimate dynamic PCU values using effective area approach under mixed traffic conditions. Data for this study were collected from four-lane divided and two-lane undivided urban mid-block sections located in Indian cities for six hours on a typical weekday using video-graphic technique. For each vehicle type, dynamic PCU values were calculated using effective area and speed for six cases considering subject vehicle, leader and adjacent vehicles. The variations of PCU values with respect to traffic flow and facility type are also studied. PCU values were found to be higher for two-lane undivided road compared to four-lane divided road due to influence of opposing vehicles. Furthermore, estimated PCU values were validated with existing methods and found that adopted methodology is better.
Impact of Level of Service (LOS) on the Driver’s Behavior on Arterials
Danny Dadonye Brown, Morgan State UniversityShow Abstract
Mansoureh Jeihani, Morgan State University
Zohreh Rashidi Moghaddam, Morgan State University
Celeste Chavis, Morgan State University
Nabaruna Karmakar, North Carolina State University
Behzad Aghdashi, Institute for Transportation Research and Education (ITRE)
This study investigates the effect(s) of level of service on driver’s behavior using a full-scale high-fidelity driving simulator. Over 50 participants are recruited to drive through six scenarios of level of services; A through F defined in the 6th edition of Highway Capacity Manual. The driving behavior of each participant for every tenth of a second is recorded. Descriptive analysis of the data obtained as well as single-factor ANOVA reveals that as LOS deteriorates from A to F, the number of times drivers push-down on the gas/throttle pedal and the number of times the brakes are fully engaged per mile increases, while , the average extent to which the throttle is pressed; the average throttle ratio, decreases. In addition, the number of lane changes per mile per available lane increases from LOS A to F. This is an indication of driver’s eagerness to escape traffic by changing to more freely-flowing lanes. Therefore, level of aggression in drivers increases with LOS progression from A to F.
Saturation Flow Model for Signalized Intersection Under Mixed Traffic Condition
Sabyasachi Biswas, Indian Institute of Technology, RoorkeeShow Abstract
Souvik Chakraborty, Indian Institute of Technology, Roorkee
Indrajit Ghosh, Indian Institute of Technology, Roorkee
Satish Chandra, Central Road Research Institue-CSIR
Saturation flow is one of the most important functional parameters at signalized intersections. It is to be noted that saturation flow is a functional measure of the intersection operation, which indicates the performance of the intersection and its probable capacity if working in an ideal situation. However, determination of the saturation flow is a challenging task in developing countries like India where vehicles with diverse static and dynamic characteristics use the same carriageway. At the same time, it is influenced by several other factors. In this context, the present research is carried out to examine the effects of traffic composition, approach width and right turning movements on saturation flow under heterogeneous traffic conditions. This paper proposes a model for computing saturation flow at signalized intersection under mixed traffic condition based on Kriging approach. It also carried out a detailed comparison of the mean saturation flow values obtained by the conventional method, regression method and Kriging method for the study approaches. The low MAPE values (< 5%) have been obtained for saturation flow by Kriging method with respect to the conventional method. Finally, the proposed models are used to evaluate the impact of right turning vehicles on saturation flow at shared lane condition.