Merging Section Research Articles

Traffic safety analysis of inter-tunnel weaving section with conflict prediction models

With increasing traffic demand in urban areas of metropolises, many tunnels have been constructed to improve road capacity and traffic mobility. The distance between two consecutive tunnels is relatively short which usually forms a weaving section, leading to considerable traffic conflicts. The objective of this study is to evaluate the safety performance of such inter-tunnel sections. Conflict prediction models based on negative binomial regression were developed to identify influential factors. Field data were collected at ten selected sites in Nanjing, China, and used for calibrating and validating the proposed models. Two types of inter-tunnel weaving sections (type 1 and type 2) were found in the field with distinct lane markings and operation rules. The unique lane markings in type 1 weaving sections are designed to isolate weaving traffic flows and thus reduce conflicts, but in practice, contradictory to its design intention, lead to more traffic conflicts compared with type 2 weaving sections. In addition, the length of the diverging section, merging section, and whole weaving section are found to be significant influencing factors on the conflict occurrence. The findings in the present study are expected to help engineer better design inter-tunnel sections.

A Hierarchical Model-Based Optimization Control Approach for Cooperative Merging by Connected Automated Vehicles

Gap selection and dynamic speed profiles of interacting vehicles at on-ramps affect the safety and efficiency of highway merging sections. This paper puts forward a hierarchical control approach for Connected Automated Vehicles (CAVs) to achieve efficient and safe merging operations. A tactical layer controller employs a second-order car-following model with a cooperative merging mode to represent a cooperative merging process and generates an optimal vehicle merging sequence and time instants when on-ramp CAVs start to adapt their speeds and positions to prepare merging into the target gaps respectively. An operational layer controller is designed based on Model Predictive Control (MPC). It uses a third-order vehicle dynamics model and optimizes desired accelerations for CAVs and the time instants when the on-ramp CAVs initiate the lane-changing executions respectively. Both the tactical layer controller and operational layer controller derive their control commands by minimizing an objective function for different time horizons. The objective function penalizes deviations of CAVs’ inter-vehicle gaps to their desired values, relative speeds to their direct predecessors, and actual or desired accelerations, subject to constraints on velocities, actual or desired accelerations, and inter-vehicle gaps. The performance of the proposed hierarchical control framework and a benchmark on-ramp merging method using a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">first-in-first-out</i> rule to determine the merging sequence is demonstrated under 135 scenarios with different initial conditions, desired time gap settings, and numbers of on-ramp vehicles. The experimental results show the superiority of the hierarchical control approach.

Evaluating Traffic Efficiency and Safety by Varying Truck Platoon Characteristics in a Critical Traffic Situation

Truck platooning is the application of cooperative adaptive cruise control where multiple trucks are electronically linked using vehicle-to-vehicle communication. Although truck platoons might bring fuel savings and emission reductions, their interactions with surrounding traffic and resulting impact on traffic operations and safety are not fully understood. The objective of this paper is to evaluate traffic efficiency and safety in a critical traffic situation when truck platoons are introduced in the system. This paper presents a case study of a merging section, located on A15 motorway, near the port of Rotterdam in the Netherlands. We consider two scenarios: platoons on a mainline carriageway and platoons merging onto a mainline carriageway. We simulate the movements of truck platoons in a microscopic traffic simulator. Longitudinal and lateral controllers for truck platoons, proposed in this paper, can ensure their collision-free, string-stable, and smooth driving behavior. Simulation experiments are conducted by varying platoon characteristics such as market penetration, length, intra-platoon headway, platoon speed, and their ability to create a gap for changing lanes. The results suggest that truck platoons on the mainline carriageway may be detrimental to traffic efficiency and safety in high traffic intensity, whereas truck platoons originating from an on-ramp produce limited impacts. Further, we conduct both local and global sensitivity analyses to analyze the impact of platoon characteristics on traffic efficiency and safety. The findings emphasize that uncertainty in traffic efficiency and safety strongly depends on the interactions among platoon characteristics, traffic demand, and traffic scenarios.

Traffic Flow Analysis at Cloverleaf Interchange and Check for the feasibility of Ramp-Metering at the Merging Section of Cloverleaf Interchange

Merging section is the key point at the cloverleaf interchange for the purpose to merge the vehicle from Ramp to Freeway. This section is the potential for traffic crashes due to the composition of two traffic flow for the same space. This study proposes feasible of Ramp-meter at the merging section. Spot speed of different types of vehicles has been extracted from the videography data. Classified volume count at Ramp and freeway has been calculated for the traffic flow analysis. Speed-Flow-Density of the heterogeneous traffic can be modeled from the extracted data. The Speed-Flow-Density curve was plotted. This study proposes a linear regression model and simulation using PTV VISSIM at the merging section at the ramp. From the simulation, we can define the feasibility of the proposing of the Ramp-metering at the merging section. From this paper, we came to know about the recommendation for the feasibility criteria for the ramp and improvement for the existing merging section

A Review on Handicap Sections and Situations to Improve Driving Safety of Automated Vehicles

An automated vehicle performs self-driving by utilizing information gathered through sensors attached to the vehicle. Sensor accuracy is thus mentioned as the major technology for enhancing driving safety. However, since urban centers are replete with sections and situations that handicap driving such as sensor recognition limitations and failures, it is necessary to conduct a study that prepares for driving handicaps. As such, this study aims to derive the sections and situations where driving safety is depreciated and review those problems via an analytic hierarchy process (AHP) analysis on driving handicap factors. The analysis result showed that the importance of these handicap situations is high, and it was confirmed that it is necessary to first review off-road sections, environmental factors (heavy rain or snow), merge sections, and sections with poor lane conditions. The result of this research has significance in reviewing road sections and potential situations that require primary verification for securing the driving safety of automated vehicles. It is expected to be utilized in the relevant studies as a basic study.

Goal Estimation of Mandatory Lane Changes Based on Interaction between Drivers

In this paper, we propose a novel method to estimate a goal of surround vehicles to perform a lane change at a merging section. Recently, autonomous driving and advance driver-assistance systems are attracting great attention as a solution to substitute human drivers and to decrease accident rates. For example, a warning system to alert a lane change performed by surrounding vehicles to the front space of the host vehicle can be considered. If it is possible to forecast the intention of the interrupting vehicle in advance, the host driver can easily respond to the lane change with sufficient reaction time. This paper assumes a mandatory situation where two lanes are merged. The proposed method assesses the interaction between the lane-changing vehicle and the host vehicle on the mainstream lane. Then, the lane-change goal is estimated based on the interaction under the assumption that the lane-changing driver decides to minimize the collision risk. The proposed method applies the dynamic potential field method, which changes the distribution according to the relative speed and distance between two subject vehicles, to assess the interaction. The performance of goal estimation is evaluated using real traffic data, and it is demonstrated that the estimation can be successfully performed by the proposed method.

Modeling two-vehicle interaction at freeway-on ramp merging section with game theory

Modeling two-vehicle interaction at freeway-on ramp merging section with game theory

A dynamic merge assistance method based on the concept of instantaneous virtual trajectory for vehicle-to-infrastructure connected vehicles

Lane-changing activities near freeway merging, diverging, and weaving sections are one of the major factors leading to recurrent bottleneck congestion. In recent years, microscopic dynamic merging assistance (DMA) methods are found efficient to improve mobility and safety in merging areas. The article proposes a solution, the connected vehicle (CV) vehicle-to-infrastructure (V2I)-based dynamic merge assistance (DMA) method, analyzing vehicle trajectory data collected at CV roadside units (RSU) and implements a “vehicle-gap” pairing process for vehicle-gap synchronized control. The vehicle-gap pairing is determined by dynamically predicting their merging potential per the relationship between the “instantaneous virtual trajectories” (IVTs) of mainline and onramp vehicles. The IVTs are generated according to the prevailing speed profiles on both ramp and mainline through lane. Other than those automated control-based methods, this article focuses on providing a realistic speed instruction to human drivers through CV communication. A Cooperative Adaptive Cruise Control model is adopted to calculate such speed instruction. The paired onramp/mainline vehicles who follow the speed instruction can form a putative platoon so that their speed and location can be synchronized all through the merging area to ensure the gap-opening and catching-up. The proposed method is evaluated within a simulation network based on the field data collected on Interstate 35 at Austin, TX. The proposed method is tested in a microscopic traffic simulation environment using VISSIM external driver model Application Programing Interface. The simulation results indicated significant reduced average travel time at merge sections during congestion and increased time-to-collision during merging compared with other existing microscopic merge control models.

Speed reduction on merging sections in mixed traffic: a case study

Driver behavioral studies on merging sections in mixed traffic conditions constituting weak lane discipline are not explicitly studied. This paper provides a case study on vehicle merging process and evaluates speed reduction at merging sections for different vehicle types with various vehicle compositions and flow levels. It provides a literature of research on merging traffic. Further, it explores parameters necessary to be adopted for mixed traffic conditions. Speed reduction on a 2 lane main road due to merging of a two lane ramp section in Navi Mumbai, India is studied by calculating traffic speed and flow levels at various sections before and after the merging. Vehicle type wise speed reduction is evaluated. The result indicated that traffic speeds on main road and ramps are significantly affected due to the increase in flow levels on the ramp. Further, increase in percentage of two wheelers also cause a reduction in speed. However, composition of heavy vehicles do not have a significant effect on speed reduction. Cars constitute the maximum reduction in speed among all vehicle types studied. The results of this study provide a measure of effectiveness of the merging section. Reduction in speed causes delays and affect travel times over a larger network, thus effective management of traffic on merging sections can include innovative ways to improve traffic speeds.

Abdominal drain straying into right atrium: a case report

BackgroundA drain exchange with the use of a guidewire may be accompanied by serious complications.Case presentationThis case involved an 86-year-old man with overlapping cancers of intrahepatic cholangiocarcinoma and perihilar cholangiocarcinoma. A left hepatectomy, a left caudal lobectomy (with a medial hepatic vein preservation), an extrahepatic bile duct resection, and a right hepatojejunostomy were performed. The abdominal drain was placed into the hepatectomy side. Bile leakage occurred on the seventh day after the surgery, and the drain was exchanged. Since the bile leakage was still detectable via a computed tomography (CT) scan on the 15th postoperative day, the drain was exchanged again. On the next day, blood had discharged from the drain. A CT scan revealed that the tip of the drain was straying into the right atrium (RA) and the drain was removed from the inferior vena cava (IVC) under general anesthesia. One week later, a fiburin thrombus was observed from the IVC to the RA via the use of transthoracic echocardiography. A right atrial incision, a thrombus removal, and a middle hepatic vein merging section closure surgery were performed. Afterward, the patient’s general condition gradually improved, and he was transferred to the hospital for rehabilitation.ConclusionMore careful guidewire operations are necessary at the time of the exchange of the drain to prevent the drain from being placed too close to blood vessels.

Investigating the impact of dynamic merge control strategies on driving behavior on rural and urban expressways – A driving simulator study

Harsh decelerations and abrupt lane changes of drivers on the outer expressway lane in response to merging platoon vehicles from on-ramps increase the crash- and congestion risk on expressways. Several merge control approaches are worldwide implemented. However, there is a gap in knowledge which driving behaviors determine whether a particular merge control approach is best for a rural or urban expressway. This study tests a number of dynamic merge control strategies, such as lane control signalization (eventually combined with variable speed limits (VSL), on a 4-lane urban and rural expressway to measure the behavioral responses of drivers being directly exposed to platoon merging from on-ramps. Subsequently, a comparison was made with the driving behaviors in response to static merge control (e.g. merge warning signs or road marking treatment). The driving behavior of 66 drivers from the State of Qatar was recorded in a driving simulator and analyzed by means of a within-subject repeated measures analysis with univariate statistics. The results suggest that dynamic merge control is more effective for rural expressways considering the higher traffic speeds. The earlier lane changes contributed to smooth maneuvers and gradual speed reductions on the rural expressway and improved safe driving behavior as compared to static merge control. In contrast, the dynamic merge control did not deliver additional safety benefits on urban expressways and can be substituted by a low-cost static merge control approach. Policymakers aiming to improve traffic safety at expressway merging sections are advised to take the speed characteristics of the local expressway into account before implementing dynamic merge control.

Examining Traffic Flow Parameters at Merging Section on High-Speed Urban Roads in India

Examining Traffic Flow Parameters at Merging Section on High-Speed Urban Roads in India

Impact of Autonomous-Vehicle-Only Lanes in Mixed Traffic Conditions

The introduction of autonomous vehicles (AVs) in the near future will have a significant impact on road traffic. AVs may have advantages in efficiency and convenience, but safety can be compromised in mixed operations of manual vehicles and AVs. To deal with the issues associated with mixed traffic and to avoid its negative effects, a special purpose lane reserved for AVs can be proposed to segregate AVs from manual vehicles. In this research, we analyze the effect on efficiency and safety of AVs in mixed traffic and in a situation where an AV-only lane is deployed. In the analysis, we investigate the average speed, the throughput, and the inverse time-to-collision (ITTC). We differentiate the behaviors of manual vehicles and AVs through the reaction time, desired speed, and car-following models. As a result, we observe that the efficiency is improved when the market penetration rate of AVs increases, especially when the highway throughput increases by up to 84% in the case of mixed traffic. However, safety worsens when the market penetration of AVs is under 40%. In this case, the average speed can be improved and the frequency of dangerous situations (ITTC &gt; 0.49) can be reduced drastically in the merging section by making the innermost lane AV-only. Accordingly, we conclude that AV-only lanes can have a significant positive impact on efficiency and safety when the market penetration rate of AVs is low.

Exploring Traffic Congestion on Urban Expressways Considering Drivers’ Unreasonable Behavior at Merge/Diverge Sections in China

The mechanisms of traffic congestion generation are more than complicated, due to complex geometric road designs and complicated driving behavior at urban expressways in China. We employ a cell transmission model (CTM) to simulate the traffic flow spatiotemporal evolution process along the expressway, and reveal the characteristics of traffic congestion occurrence and propagation. Here, we apply the variable-length-cell CTM to adapt the complicated road geometry and configuration, and propose the merge section CTM considering drivers’ mandatory lane-changing and other unreasonable behavior at the on-ramp merge section, and propose the diverge section CTM considering queue length end extending the expressway mainline to generate a dynamic bottleneck at the diverge section. In the new improved CTM model, we introduce merge ratio and diverge ratio to describe the effect of driver behavior at the merge and diverge section. We conduct simulations on the real urban expressway in China, with results showing that the merge section and diverge section are the original location of expressway traffic congestion generation, and on/off-ramp traffic flow has a great effect on the expressway mainline operation. When on-ramp traffic volume increases by 40%, the merge section delay increases by 35%, and when off-ramp capacity increases by 100 veh/hr, the diverge section delay decreases about by 10%, which proves the strong interaction between expressway and adjacent road networks. Our results provide the underlying insights of traffic congestion mechanism in urban expressway in China, which can be used to better understand and manage this issue.

Unravelling effects of cooperative adaptive cruise control deactivation on traffic flow characteristics at merging bottlenecks

Cooperative Adaptive Cruise Control (CACC) systems have the potential to increase roadway capacity and mitigate traffic congestion thanks to the short following distance enabled by inter-vehicle communication. However, due to limitations in acceleration and deceleration capabilities of CACC systems, deactivation and switch to ACC or human-driven mode will take place when conditions are outside the operational design domain. Given the lack of elaborate models on this interaction, existing CACC traffic flow models have not yet been able to reproduce realistic CACC vehicle behaviour and pay little attention to the influence of system deactivation on traffic flow at bottlenecks. This study aims to gain insights into the influence of CACC on highway operations at merging bottlenecks by using a realistic CACC model that captures driver-system interactions and string length limits. We conduct systematic traffic simulations for various CACC market penetration rates (MPR) to derive free-flow capacity and queue discharge rate of the merging section and compare these to the capacity of a homogeneous pipeline section. The results show that an increased CACC MPR can indeed increase the roadway capacity. However, the resulting capacity in the merging bottleneck is much lower than the pipeline capacity and capacity drop persists in bottleneck scenarios at all CACC MPR levels. It is also found that CACC increases flow heterogeneity due to the switch among different operation modes. A microscopic investigation of the CACC operational mode and trajectories reveals a close relation between CACC deactivation, traffic congestion and flow heterogeneity.

A Novel Safe Merging Algorithm for Connected Vehicles Using NetLogo

In this paper, we present two new algorithms for MetroCar System (MCS) vehicles at a merging zone. First algorithm states the regulations of vehicles in the same road such as control the following vehicle’s to prevent collision with the frontier vehicle. Second algorithm is for merging section of roads in order to prevent any collision at merging point. The proposed algorithms are verified and validated by using simulation results of the NetLogo simulation software. The simulation results show that the proposed algorithms guarantees that no collision occur at the merging zone.DOI: http://dx.doi.org/10.5755/j01.eie.24.3.20956

Analogical Model of Merging Process in Urban Transportation System by Application of Oblique Shockwave Theory

Congestion in the merging roadways cannot be neglect, and it is necessary to build merging roadways in more massive scale by addressing it. In this paper, we compare the oblique shockwave in aerodynamic with the dynamic process in the merging roadways. Besides, we present the formation of the oblique shock wave in the turning section and merging section. Based on the similar mechanics between airflow and traffic flow, a traffic oblique shockwave model is proposed to explain the mechanics between the merging stream and the stream from the upstream. With this analogical model, we can obtain more regularities of the process of merging roadways.

Some traffic characteristics of rural roads in Iraq

Now a days, modeling traffic characteristics are very important in evaluating traffic facilitates such normal section, weaving and merging sections. Lane changing and lane utilization are important traffic characteristics that are widely studied. Therefore this study is focused on both of these. The lane changing behavior affects the capacity and safety of roads. The distribution of vehicles among lanes of roadway is important in terms of different aspects such as safety, traffic management and even the structural design of roads. Field data have been collected from different rural roads. Two types of roads were studied; two-lane section and three-lane section. The results of analysis for collected data indicate that the driver behaviour is different in terms of lane utilization in Iraq from other countries and the same behaviour was found for lane changes also. Compared to other countries, Iraq has the lowest lane utilization and highest frequency of lane changes. These data are urgently needed nowadays for calibrating and validating the sophisticated programs such as simulated microscopic programs. These data are so important to mimic the reality for driver behaviors in rural roadways.

Evaluation of the Traffic Performance Measure for Exclusive Motorcycle Lane at Merging Section

Exclusive Motorcycle Lane (EML) is defined as a roadway meant exclusively for motorcycles or can be stated as motorcyclists who are compelled by law to use it and other vehicles are prohibited by law from using it. It is physically separated from the mainstreams carriageway and is grade separated from the main carriageway at intersections, interchanges or points of conflicts. Merging is one of the parts of way that motorcycle deceleration the speed from main stream lane to enter the Exclusive Motorcycle Lane (EML) with safe. The urban expressways in Malaysia have serious problems regarding the safety, efficiency and comfort ability at merging sections of an EML because of the insufficient geometric due to limited land and the right of way design configuration condition. The increase of traffic volume and demand lead towards the degradation of motorcyclist performance while on their wheels. This research is performed in order to achieve the objectives, i.e. to obtain and analyze local empirical data, such as flow rate, headway and speed on exclusive motorcycle lane at merging section that reflects on the local traffic condition on Federal Highway Route 2, and to obtainregression modeling that relates to Flow Rate with regards to the Headway 1-3, Time Mean Speed and Length of Merging Ramp section, Lm on the merging section of EML and merging ramp section. Tworegression models have successfully been performed with R-Sq 94.8 % for EML section and 31.1 % for merging ramp section. Its also highlighted the attributes of EML.

Pedestrian crowd dynamics in merging sections: Revisiting the “faster-is-slower” phenomenon

The study of the discharge of active or self-driven matter in narrow passages has become of the growing interest in a variety of fields. The question has particularly important practical applications for the safety of pedestrian human flows notably in emergency scenarios. It has been suggested predominantly through simulation in some theoretical studies as well as through few experimentations that under certain circumstances, an elevated vigour to escape may exacerbate the outflow and cause further delay although the experimental evidence is rather mixed. The dimensions of this complex phenomenon known as the “faster-is slower” effect are of crucial importance to be understood owing to its potential practical implications for the emergency management. The contextual requirements of observing this phenomenon are yet to be identified. It is not clear whether a “do not speed up” policy is universally beneficial and advisable in an evacuation scenario. Here for the first time we experimentally examine this phenomenon in relation to the pedestrian flows at merging sections as a common geometric feature of crowd egress. Various merging angles and three different speed regimes were examined in high-density laboratory experiments. The measurements of flow interruptions and egress efficiency all indicated that the pedestrians were discharged faster when moving at elevated speed levels. We also observed clear dependencies between the discharge rate and the physical layout of the merging with certain designs clearly outperforming others. But regardless of the design, we observed faster throughput and greater avalanche sizes when we instructed pedestrians to run. Our results give the suggestion that observation of the faster-is-slower effect may necessitate certain critical conditions including passages being overly narrow relative to the size of participles (pedestrians) to create long-lasting blockages. The faster-is-slower assumption may not be universal and there may be circumstances where faster is, in fact, faster for evacuees. In the light of these findings, we suggest that it is important to identify and formulate those conditions so they can be disentangled from one another in the models. Misguided overgeneralisations may have unintended adverse ramifications for the safe evacuation management, and this highlights the need for further exploration of this phenomenon.