Merging Section Research Articles

輸送システム合流部のモデル化とその解析

輸送システム合流部のモデル化とその解析

EMI's TwinGun Concept for a New Light-gas Gun Type Hypervelocity Accelerator

A new two-stage light-gas gun type accelerator was developed at Fraunhofer EMI. The accelerator features two parallel pump tubes that are attached to a single powder chamber. Loading conditions are adjusted to achieve a small delay between the arrival of the two pistons at their respective accelerated reservoir. A merging section combines both gas channels and guides the two pressure pulses generated to a single launch tube breech. The two pressure pulses merge to a single, but elongated pressure pulse that acts on the projectile. Carefully adjusting the loading conditions shall in the future increase the performance compared to standard light-gas gun accelerators. Initial experimental results of the calibre 4 mm prototype show feasibility of the concept.

Creating practical cyborgs

In this paper we consider the creative realisation of new beings — namely, cyborgs. These can be brought about in a number of ways, and several versions are discussed. A key feature is merging biological and technological sections into an overall living operational whole. A practical look is taken at how the use of implant and electrode technology can be employed to open up new paths between humans/animals and technology, especially linking the brain directly with external entities. Actual experimentation in each of the different cyborg forms perhaps defines the paper’s contents more than anything else. Considered are RFID implants, magnet implants, deep brain stimulation, Braingate implants and growing biological brains in robot bodies.

Research on Traffic Safety on Freeway Merging Sections Based on TTC and PET

Since the traffic safety of freeway interchange merging sections and the accidents occurred in this areas can not meet the requirement of statistical analysis, this paper employed traffic conflict technique to analyze the safety situation of freeway merging sections. The traffic data of vehicles through the merging sections are collected and analyzed. These data include the vehicle type, speed, time headway and others based on the features of individual vehicle. Then two methodologies are developed, the first is based on time to collision (TTC), which can calculate the rear-end conflict number, while the second is based on post encroachment time (PET), which can calculate the lane-change conflict number. The results show that these surrogate measures can quantitatively describe the rear-end conflict situation and lane-change conflict situation.

An Analysis of Merging Maneuvers at Urban Expressway Merging Sections

This study analyzed merging maneuvers namely merging speed and merging position by using video data collected at two merging sections on Nagoya Urban Expressway, Japan. The analysis demonstrated that the longer acceleration lane length is associated with further merging positions. Furthermore, the traffic conditions do not significantly affect the means of merging positions but their variations. The variations of merging positions become significant when the density of mainline is higher. A similar tendency can be observed if acceleration lane length becomes longer. Regarding merging speed, it is found that mainline traffic conditions significantly affect merging speeds. They decrease as traffic conditions become denser. To generalize the results of analysis, a normal distribution was adopted to fit the models of merging position and speed. The results of model estimation and sensitivity analysis indicate that the models give consistent results with the analysis.

Modeling Speed Adjustment Behavior of Merging Vehicles at Urban Expressway Merging Sections

This paper modeled speed adjustment behavior of merging vehicles by using video data collected at two merging sections on urban expressway in Nagoya City, Japan. The results showed that the longer acceleration lane results in a higher acceleration rate of merging vehicles. And the denser mainline traffic causes a lower that of merging vehicles. In addition, the leading and following time to collision (TTCL and TTCF) were adopted as variables. It is found that if TTCL is negative, merging vehicles increase their acceleration rate. By contrast, if TTCL becomes positive and the collision can happen, merging vehicles tend to reduce acceleration rate to avoid the collision with leading mainline vehicles. In case of TTCF, the positive signs of coefficients indicate that when following mainline vehicles run faster than merging vehicles, they increase their acceleration rate to avoid collision with following mainline vehicles. Furthermore, the validation results suggest a promising applicability of the developed models.

Analysis of the Lane-Change Behavior at Lane Closure by Driving Simulation Experiment

To mitigate the traffic congestion at merging sections in urban expressway networks, a dynamic lane operation is being studied in Japan, which dynamically switches one lane to either approach of a merging section with more traffic demand. To evaluate the safety concern, the lane-change behavior when one lane is closed by variable barrier which is informed by variable message sign (VMS) is analyzed in this study. A driving simulation experiment is conducted for the analysis considering the implementation of the dynamic lane operation for merging sections at Route C1 of Tokyo Metropolitan Expressway. Traffic condition and the distance between a lane-closure point and the VMS are considered as critical factors affecting the risky behavior, and their influence on the lane change behavior is studied.

Capacity Estimation for On-Ramp Merging Section of Urban Expressway Based on Time Headway Loss

This paper proposes a model for estimating capacity of on-ramp merging section of urban expressway based on dynamics and gap acceptance theory, considering lane-changing processes and time headway loss. Survey data were collected from on-ramp merging sections of shanghai urban expressway system and showed that capacity drop of on-ramp merging section is caused by drivers’ lane-changing which may lead to unsteady speed of vehicles and so prolonged time headway compared to the minimum time headway corresponding to the maximum capacity. Three parameters (optimal time headway, time headway loss, and interference quantity of lane-changing) are given and a methodology by accumulating time headway loss due to lane-changing is developed to estimate the capacity drop. Results’ comparisons between real data and microsimulation of on-ramp merging sections and sensitivity analysis show that the proposed model can produce reliable and accurate results. This study also reveals that ramp flow and the difference between the optimal speed and the lane-changing speed of fleet have a great impact on capacity drop. This study is beneficial to evaluate congestion levels, to understand complex traffic phenomena, and so to find efficient solutions.

Analysis of Congestion Phenomena on the One Lane Dropped Motorway Merge without Ramp-metering in İstanbul

Motorway merges are typically congestion areas because of irregularities on lanes between upstream and downstream directions. At motorway merges, it is obvious that when the upstream and/or on-ramp flow is greater than the downstream (bottleneck) capacity, congestion arises. Therefore, queue will form and grow in relation with the demand and bottleneck capacity. The aim of this paper is to analyze the effect of mainstream and on-ramp flows on the congestion phenomena. As there is no ramp-metering application in Istanbul, on-ramp flow has an excessive effect on the congestion. In this study, macroscopic merge behavior is analyzed at one crucial motorway merge in Istanbul. Traffic data is obtained by Remote Traffic Microwave Sensors (RTMS) operated by the Municipality of Istanbul. RTMS data consists of volume, speed, occupancy and heavy vehicle counts per lane while minimum data collection interval is 2minutes. Examined motorway merge section, main stream and on-ramp flows are observed by separate RTMS. Whole year weekday data of 2012 is used for analysis. It is seen that mainstream flow rate changes from 3360 pcph to 6210 pcph before congestion depends on the on-ramp flow rate that varies from 1755 pcph to 3060 pcph. In addition, on-ramp ratio is found between 0.23 and 0.43 which cause congestion on this motorway merge.

Validation of a Macroscopic Lane-Changing Model

Systematic lane changes inside a weaving area could lead to accidents and disrupt the entire traffic flow. Recently, a simple macroscopic lane-changing model that determines the number of lane changes from on-ramp flows and the number of lanes was proposed to describe traffic dynamics inside the lane-changing area at a merging section. However, this macroscopic lane-changing model had not been validated with vehicle trajectory data. This study attempted to fill that validation gap. First, lane changes were categorized into two types: left-lane changes and right-lane changes. Then the following two hypotheses derived from the macroscopic lane-changing model were validated: (a) the number of left-lane changes within two adjacent lanes linearly increases from the leftmost lane to the shoulder lane and (b) the number of left-lane changes linearly increases with the flow rate of on-ramp vehicles inside the lane-changing area. Traffic balance among lanes was analyzed, and the two proposed hypotheses were validated for different periods and road geometries by using NGSIM vehicle trajectory data. The validation results confirm that the two linear relationships in the macroscopic lane-changing model exist.

MODELING GAP CHOICE BEHAVIOR AT URBAN EXPRESSWAY MERGING SECTIONS

This paper proposes an approach to model the gap choice behavior of merging vehicles under various traffic flow conditions at urban expressway merging sections in Nagoya, Japan. The gap choice is classified into three patterns denoted direct, yield and chase merging. Empirical analysis shows that mainline traffic conditions significantly affect the proportion of gap choice. In addition, yield and chase choices result in further merging position compared to direct one. This fact is necessary to be considered in order to design the acceleration lane to meet driver behavior under relevant operational traffic flow conditions. TTC is adopted as an index to determine the threshold of choosing a merging pattern. The results show that the thresholds of choosing direct/yield or chase, continue to chase or not and direct or yield are 4.3, 3.2 and 5.4 seconds, respectively. The gap choice behavior is modeled by applying binary logit model. The results reveal that relative speed and space gap, traffic conditions, acceleration lane length, and remaining distance significantly affect the gap choice behavior of merging drivers.

Use of Computer Vision Data for Detailed Driver Behavior Analysis and Trajectory Interpretation at Roundabouts

With recent important upgrades to North American intersection design guides, roundabouts are gaining popularity as a method of reducing road conflicts, streamlining flow, and curbing excessive speeding at busy intersections. The current design approach, however, makes use of mean spot speed measures and design criteria that do not take into account yielding behavior and acceleration and deceleration, all of which may be affected by regional driving culture and local roundabout design. This research paper introduces the methodology being developed for the detailed analysis of driving behavior, trajectory interpretation, and conflict measures in modern North American roundabouts, based on video data extracted by means of computer vision. The analysis explores the methods used to prepare microscopic speed maps, compiled speed profiles, lane-change counts, and gap time measures. The paper introduces and discusses the interpretation of trajectories at the scale of roundabout merge sections instead of looking at safety from the point of view of a roundabout as a unified system. The research found significant variation in distributions of speed across five case study roundabouts in the province of Quebec, Canada; this result may be explained by regional differences in design and road use. The paper also found aggressive gap times and uneven traffic flow as contributing factors to speed.

Assessing Countermeasures Designed to Reduce Hazards Between Bike Lane Occupants and Right-Turning Automobiles in China

Transportation professionals in China are facing challenges resulting from increased conflicts between various transportation modes in mixed traffic. This research examines practical and low-cost measures that could reduce the number of conflicts at intersections between bike lane occupants and right-turning vehicles, while maintaining or improving existing operational performance. To test different configurations, three representative intersections in Kunming, China, were analyzed using microsimulation software. The unique traffic flows and geometric layout of the intersections resulted in different alternatives being applied at each intersection. Changes included signal phase changes, such as delayed green signals and separate bicycle phasing; and geometric changes, such as the addition of turn lanes and upstream merge sections for conflicting traffic. Two main operational parameters are used to evaluate existing conditions and alternatives: delay and queue length. Each alternative was compared with the existing conditions to determine the impact on operations, while potentially reducing conflict. The addition of right-turn lanes, which displaces conflicts relative to other alternatives, yielded generally shorter queue lengths and delay, mostly because of added capacity. Partially protected through-bike signal phases proved to only slightly increase delay for most road users, and in some cases reduced delay, but could be more effective at reducing conflict than right-turn lane geometric strategies.

Analysis of traffic congestion by considering merging on entry lines in transportation system

AbstractIn a transportation system, a merging control strategy is necessary to avoid collisions between vehicles at a merging section with entry lines. In this study, under the assumption that each entry line is assigned time‐independent priority, we analyze traffic congestion with a stochastic model. A quantitative estimation of the congestion is successfully obtained in terms of the average queue length and the average queuing delay. On the basis of analytical results, we propose a control strategy that changes the priority periodically. Using simulation, it is clarified that the proposed control strategy gives arbitrary values of the queue length and the queuing delay on each line. © 2012 Wiley Periodicals, Inc. Electron Comm Jpn, 95(8): 34‐43, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/ecj.11374

A Traffic Flow Simulation Model Based on the Desired Speed in Merging Sections on Freeways

A Traffic Flow Simulation Model Based on the Desired Speed in Merging Sections on Freeways

Estimation of Capacity Drop in Highway Merging Sections

Capacity drop, which is defined as discharge flow drop after bottleneck activation, has been frequently observed on urban highways, especially in merging sections. Maintaining high capacity on roadways is a main concern for traffic operators, theorists, and transportation modelers. Accordingly, many researchers have investigated capacity drop, yet highway capacity and discharge flow measurement methods vary, and results are not comparable. A systematic methodology is introduced for finding capacity drops by using detector data to estimate roadway capacity and discharge flow. The impact of the number of lanes on capacity drops at merging sections on highways is investigated. Results show that capacity drop is negatively related to the number of lanes. Detailed information is analyzed for individual lanes and off-ramp effect on capacity drop. Individual lane analysis supports the negative relationship between the amount of capacity drop and the number of lanes. A decrease in capacity drop is observed when the flow ratio of the off-ramp increases.

Second-Order Model and Capacity Drop at Merge

This study deals with the modeling of merge sections from a macroscopic point of view. It is well known that the first-order macroscopic model is not able to reproduce the capacity drop, that is, the fact that the maximal throughput just downstream of a merge is lower after the onset of congestion than just before. Second-order models, such as the one proposed recently by Bastin and Haut, claim to be able to reproduce this observed feature. The ability of this second-order model, chosen for its generality, to reproduce the capacity drop was studied by using numerical investigations. Definitions of the capacity drop are reviewed and some of the experimental observations are reported. The latest attempts to model the capacity drop are presented. Then the chosen model is presented briefly, and its numerical resolution is detailed. The study's main contribution can then be developed. From numerical experiments, it is shown that the studied approach allows the definition of a new framework for capacity drop modeling. Its limitations are also explored.

Operation of vehicles in AGV system and method for analyzing operation

AbstractIt is important to discuss the behavior of traffic at merging sections for the design and realization of an automated guided vehicle system (AGVS). In this study, we deal with a merging section of the AGVS by considering the time limit for the merging of vehicles. Near the merging section, the traffic flow in one direction forms a queue to avoid collisions between vehicles. We present an improvement of the control strategy proposed in previous research. However, since it is difficult to analyze the mathematical model of the merging section, analysis can be performed only for the case in which the time limit is set to the least values. We also propose a method for analyzing the model for an arbitrary time limit by using a linear recurrence relation. We discuss quantitatively the influence of the time limit on the average queue length and the detour rate. © 2011 Wiley Periodicals, Inc. Electr Eng Jpn, 178(1): 56–68, 2012; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.21190

Estimation of Traffic Conflict Risk for Merging Vehicles on Highway Merge Section

This study proposed a methodology for estimating rear-end conflict risk of vehicles on freeway merge sections as a probabilistic measure. The methodology consisted of two major components. The first part estimated the merging probability of a vehicle, given its position on a merge lane. Detailed vehicle trajectory data from the Next Generation Simulation program were used to find the underlying probability density function of the merging decision. The second part derived the probabilistic risk of a merging vehicle conflicting with vehicles around it as a function of a surrogate safety measure, namely, modified time-to-collision. These two parts were combined, and an index was proposed to describe the conflict risk of each merging vehicle at each time step. With aggregation of the conflict risk over time and space, a risk map for describing the level of conflict risk could be created. A case study demonstrated the implementation of the proposed method for traffic conflict analysis in detail. The result of this study can be used to evaluate the safety level of merge sections and develop real-time traffic control strategies to reduce conflicts associated with merging traffic.

Analysis of Traffic Congestion by Considering Merging on Entry Lines in Transportation System

In a transportation system, a merging control strategy is necessary to avoid collisions between vehicles at a merging section with entry lines. In this study, under the assumption that each entry line is assigned time-independent priority, we analyze traffic congestion with a stochastic model. A quantitative estimation of the congestion is successfully obtained in terms of the average queue length and the average queuing delay. On the basis of analytical results, we propose a control strategy that changes the priority periodically. Using simulation, it is clarified that the proposed control strategy gives an arbitrary values of the queue length and the queuing delay on each line.