Weaving Sections Research Articles

Study on the traffic flow of weaving section in elevated road system with cellular automaton model

The weaving sections often turn into the bottleneck on the elevated roads. On the basis of the NS cellular automaton traffic model, the weaving section with one-lane main road was simulated and analyzed. For the free traffic flow, weaving almost has no influence on the system, even with increased weaving length. On the other hand, when the traffic flow is in congested state, weaving conflicts have negative effects on the system. The traffic condition will be improved with the increase of weaving length. Our simulation results suggest that the length of weaving sections need not to be inappropriately increased, and a proper moderate value should be chosen to get an optimal traffic condition.

Stochastic Processes of Moving Bottlenecks: Approximate Formulas for Highway Capacity

This paper presents a general framework for developing formulas to estimate the capacity of freeway bottlenecks caused by the presence of slow vehicles. These underperforming vehicles may represent trucks on an uphill grade, cautious lane changers at a weaving section, or any other stream of vehicles moving consistently—at least for a short period of time—more slowly than prevailing traffic. From modeling of the under-performing stream as simplified yet realistic stochastic processes, closed-form expressions for the segment's capacity can be obtained. Four such processes are presented and exemplified for the case of short uphill grades, a type of facility where existing capacity formulas fail. The proposed models—which do not need calibration—improve current estimates, and one in particular explains existing data with remarkable accuracy.

Stochastic Processes of Moving Bottlenecks

This paper presents a general framework for developing formulas to estimate the capacity of freeway bottlenecks caused by the presence of slow vehicles. These underperforming vehicles may represent trucks on an uphill grade, cautious lane changers at a weaving section, or any other stream of vehicles moving consistently—at least for a short period of time—more slowly than prevailing traffic. From modeling of the underperforming stream as simplified yet realistic stochastic processes, closed-form expressions for the segment's capacity can be obtained. Four such processes are presented and exemplified for the case of short uphill grades, a type of facility where existing capacity formulas fail. The proposed models—which do not need calibration—improve current estimates, and one in particular explains existing data with remarkable accuracy.

DERIVATION OF CONTINUUM TRAFFIC MODEL FOR WEAVING SECTIONS ON FREEWAYS

This paper presents a new continuum model describing the dynamics of multiclass traffic flow on multilane freeways including weaving sections. In this paper, we consider a specific freeway weaving type, which is formed when an on ramp is near to an off ramp and these two ramps are joined by an auxiliary lane. Traffic interactions in this weaving zone are very complex due to the involvement of weaving flows and non-weaving flows in the so-called mandatory lane-changing process. To handle this complexity, it is essential to have a good understanding of the (microscopic) driving behavior within the weaving zones. These behaviors are modeled based on a gap-acceptance model. The methodology to obtain a weaving continuum traffic model is thus twofold. On the one hand, we develop a (macroscopic) model to determine the mandatory lane-changing probability based on a renewal process. On the other hand, we implement the lane-changing model into a current gas-kinetic traffic flow model for heterogeneous traffic flow on multilane roadways. From this, corresponding macroscopic model is obtained based on the method of moments.

THE BEHAVIOR ANALYSIS ON A NEW TYPE WEAVING SECTION

The purpose of this research, it is analytically the interrelations between the traffic flow characteristics that include traffic density, rate of flow, and speed (k, q, and u) into completely congestion traffic conditions. This study investigates the macroscopic models of traffic flow characteristics on a new weaving section on the Taiwan National Freeway Systems, focusing on the interrelations between the traffic speed, density, and rate of flow of the congestion traffic conditions. The analysis based on these driver behaviors includes 100% lane-changing and 65.22% weaving activities. The results for this study show the fundamental interrelation of traffic flow characteristics on the completely congestion traffic flow condition similar to Greenshield model and showing no influence on lane changing and weaving activities. These regression models concludes that the critical density is 55.74 vehicles per kilometer, the speed is 34.29 kilometer per hour, and the maximum rate of flow (capacity) is 1854 vehicles per hour per lane, respectively. These results represent that the value of traffic speed and rate of flow are same the Highway Capacity Manual (HCM) and the traffic density is more then the HCM.

INTEGRATION 2.30 Framework for Modeling Lane-Changing Behavior in Weaving Sections

The effectiveness of the INTEGRATION 2.30 model for analysis of weaving sections is validated by a comparison of the lateral and longitudinal distributions of simulated and field-observed traffic volumes categorized by origin-destination pair on nine weaving sections in the Los Angeles, California, area. The results demonstrate a reasonable degree of consistency in the spatial distribution of lane flows between simulated and field-observed traffic volumes within the weaving sections (spatial lane volume error of 250 veh/h or 25%). Furthermore, the spatial distribution of lane changes across the weaving lanes matches field-observed trends. Finally, the study demonstrates how the use of optional lane-bias and lane-changing parameters can enhance the consistency between model results and field data. Overall the study demonstrates the flexibility of the INTEGRATION software for the modeling of weaving sections.

Safety aspects of freeway weaving sections

One source of vehicle conflict is the freeway weaving section, where a merge and diverge in close proximity require vehicles either entering or exiting the freeway to execute one or more lane changes. Using accident data for a portion of Southern California, we examined accidents that occurred on three types of weaving sections defined in traffic engineering: Type A, where every merging or diverging vehicle must execute one lane change, Type B, where either merging or diverging can be done without changing lanes, and Type C, where one maneuver requires at least two lane changes. We found no difference among these three types in terms of overall accident rates for 55 weaving sections over one year (1998). However, there were significant differences in terms of the types of accidents that occur within these types in terms of severity, and location of the primary collision, the factors causing the accident, and the time period in which the accident is most likely to occur. These differences in aspects of safety lead to implications for traffic engineering improvements.

Objective Analysis of Traffic Conflict and Modeling of Vehicular Speed Adjustment at Weaving Section

In order to make effective plans of comprehensive traffic safety measures including the application of ITS technology, it is important to evaluate objectively the risk of traffic accidents for road sections. The microscopic data on vehicular movements required for the analysis are extracted from video data using the image processing technique. Especially, the objective indices to evaluate traffic conflicts are used for the analysis of the risk of vehicle collision at a weaving section. As an initial stage for developing a microscopic traffic simulation, this study analyzes the speed adjustment processes of the vehicles in the lane-changing situation.

Freeway Weaving: Comparison of Highway Capacity Manual 2000 and Dutch Guidelines

Weaving sections are a commonly adopted freeway facility both in the United States and in Europe. Knowledge about the capacity and level of service achievable on different types of weaving segments is necessary for the design and management of freeways. Guidelines such as those of the U.S. Highway Capacity Manual (HCM) provide capacity values for different weaving configuration types. The Dutch guidelines for the design of weaving segments are compared with those of the U.S. HCM. Differences between their respective approaches are identified, and a comparison of capacity values is conducted. It was found that there are large differences in capacity estimates for certain weaving configuration types. The results of a sensitivity analysis explain these differences in capacity values to a large extent. This analysis showed that it is important to consider the weaving proportions per leg. Currently, neither the HCM nor the Dutch approach considers different weaving flows per incoming leg. The introduction of an additional variable into the calculation procedure that takes into account the presence of asymmetrical weaving flows is recommended.

Simulation of Freeway Weaving Areas

The operation of freeway weaving sections is characterized by intense lane-changing maneuvers and complex vehicle interactions that often create bottlenecks along freeway facilities. The CORSIM microscopic simulation model was applied to simulate the operation of eight realworld weaving sites in California under a wide range of operating conditions. The results indicate that CORSIM with default parameter values underpredicts the speeds in the weaving section by about 19% on average. Numerous simulation runs were made with different values of the model parameters. The following parameters were found to significantly affect the CORSIM results: ( a) car-following sensitivity factor, ( b) lane-changing aggressiveness factor, and ( c) percentage of freeway through vehicles that yield to merging traffic. The calibrated CORSIM model reasonably replicated observed traffic operations at all test sites. The predicted average speeds were within ±5 mph for most test sites. Good agreement between measured and predicted values was obtained for all the combinations of design characteristics and demand patterns.

The use of computer vision in monitoring weaving sections

This paper presents algorithms for vision-based monitoring of weaving sections. These algorithms have been developed for the Minnesota Department of Transportation in order to acquire data for several weaving sections in the Twin Cities area. Unlike commercially available systems, the proposed algorithms can track and count vehicles as they change lanes. Furthermore, they provide the velocity and the direction of each vehicle in the weaving section. Experimental results from various weaving sections under various weather conditions are presented. The proposed methods are based on the establishment of correspondences among blobs and vehicles as the vehicles move through the weaving section. The blob tracking problem is formulated as a bipartite graph optimization problem.

Microscopic simulation of lane changing behaviour at freeway weaving sections

Microscopic traffic simulation models are being increasingly used to evaluate Intelligent Transportation Systems (ITS) strategies and to complement empirical data in developing new analytical procedures and methodologies. Lane changing rules are an essential element of any microscopic traffic simulation model. While most of these rules are based on theories and hypotheses, to date no attempt has been made to investigate the consistency of lane changing behaviour from microscopic simulation with empirical observations. The research presented in this paper examined this consistency at freeway weaving areas using empirical data. These data were collected in the late 1980s at several major freeway weaving sections in the State of California. The microscopic traffic simulation model INTEGRATION was used to perform simulation experiments in this research. Vehicle distributions, both total and by type of movement, were used as measures to investigate the lane changing activity that took place at these freeway areas. This examination revealed significant agreement between patterns of lane changing behaviour as observed in the field and as reproduced by microscopic simulation. Most quantitative discrepancies were shown to be a function of user-specified input data or due to some inherent limitations in the empirical data.Key words: simulation, lane changing, weaving, freeways.

Microscopic simulation of lane changing behaviour at freeway weaving sections

Microscopic simulation of lane changing behaviour at freeway weaving sections

A merging–giveway interaction model of cars in a merging section: a game theoretic analysis

In many past studies dealing with traffic phenomena in merging or weaving sections, only the influence of through traffic on the behavior of a merging car is considered in the analysis. It is, however, often seen that a through car, which runs on the most outside lane, takes a cooperative motion for the merging car called “giving way” by moving to the adjacent lane. That is, both the merging car and the through car affect one another. Because their influence is not independent from one another, it should be jointly treated in the analysis as “interaction”. This behavior is typical in merging sections, and is a dominant factor forming the traffic phenomena in a section of this type. This study develops a game theoretical model to describe the traffic behavior of a pair of merging and through cars, while explicitly considering the interaction between them. Both the merging and through cars attempt to take the best actions for themselves by forecasting the other’s action, respectively. Such a behavior is modeled as a two-person non-zero-sum non-cooperative game. Through a case study with data analysis of videotaped observation, the proposed model can be used to obtain an understanding of traffic behavior at on-ramp merging sections. ©

Effects of Inadequate Driveway Corner Clearances on Traffic Operations, Safety, and Capacity

Inadequate driveway corner clearances can result in traffic operational, safety, and capacity problems. These problems can be caused by blocked driveway ingress and egress movements, incomplete turning maneuvers, conflicting intersection turning movements, confusing right-turn signal indications, insufficient weaving and merging section lengths, and various other conflicts. The effects of driveway corner clearances on safety cannot be examined easily through safety records given the current condition of the available crash and system inventory data. This provides incentives for applying theoretical traffic conflict analysis. A simple conflict analysis showed an increase in merging and crossing conflict points for driveways situated near intersections. Inadequate corner clearance can have a capacity-reducing effect. Driveway capacity may be reduced by ( a) vehicles on the arterial blocking driveway egress movements and ( b) a decreased opportunity for left-turn egress movement on arterial streets designed for platoon progression. Intersection capacity can also be reduced by a decrease in saturation flow rates due to driveway ingress and egress movements.

Evaluating Weaving Section Designs Using INTEGRATION

The current design procedure shown in Calculation 6 of the Highway Capacity Manual (HCM) requires an exhaustive analysis of a family of possible solutions. The design is selected on the basis of minimum speeds of weaving and nonweaving vehicles for different levels of service. In this paper the use of the INTEGRATION modeling tool to evaluate the same family of possible solutions is examined. Because INTEGRATION has the ability to determine volumes in addition to speeds, it was used to select the design solution based on the ratio of demand volume to capacity. Both procedures determined that five-lane Type B weaving sections greater than 610 m (2,000 ft) in length would provide level-of-service C for the origin-destination demand pattern found in Example Calculation 6 in Chapter 4 of the HCM. Analysis of the design results also showed that the number of lanes in the core area was the most critical factor in determining weaving section capacity. The length of the core area was also found to have an impact but was less important as core length increased. Finally, the type of weaving section was found to have the least impact on capacity, especially at core areas longer than 305 m (1,000 ft).

Evaluating Weaving Section Designs Using INTEGRATION

The current design procedure shown in Calculation 6 of the Highway Capacity Manual (HCM) requires an exhaustive analysis of a family of possible solutions. The design is selected on the basis of minimum speeds of weaving and nonweaving vehicles for different levels of service. In this paper the use of the INTEGRATION modeling tool to evaluate the same family of possible solutions is examined. Because INTEGRATION has the ability to determine volumes in addition to speeds, it was used to select the design solution based on the ratio of demand volume to capacity. Both procedures determined that five-lane Type B weaving sections greater than 610 m (2,000 ft) in length would provide level-of-service C for the origin-destination demand pattern found in Example Calculation 6 in Chapter 4 of the HCM. Analysis of the design results also showed that the number of lanes in the core area was the most critical factor in determining weaving section capacity. The length of the core area was also found to have an impact ...

One-Sided Weaving Operations on One-Way Frontage Roads

Weaving vehicles can heavily affect the quality of service on a facility. Techniques to evaluate weaving on arterial streets, however, are limited. Similar to arterial streets, the traffic operations on frontage or access roads along freeways can also be heavily affected by weaving. Presented here is a technique for evaluating one-sided weaving areas along with recommended lengths of weaving areas. Data from six sites were used to develop a relationship between number of lane changes and weaving volume. The weaving sections at the sites ranged from three to four lanes and from approximately 137 to 335 m in length. Throughout the large range of volumes present (250 to 2,500 vph), there was a very strong relationship between weaving volume and lane changes. The field data were used to develop a computer simulation model. The relationships between different measures of effectiveness from the simulation model provided information on critical points in which the weaving speed begins to drop more rapidly. Weaving volumes (entrance-ramp plus exit-ramp volumes) of less than 1,500 vph are associated with unconstrained levels of service, volumes between 1,500 and 3,000 vph with constrained service, and volumes over 3,000 vph with undesirable service. Additional information from the models also demonstrated that it is desirable to have a weaving length greater than 300 m. If this length is not achievable, then the minimum length should be approximately 200 m.

One-Sided Weaving Operations on One-Way Frontage Roads

Weaving vehicles can heavily affect the quality of service on a facility. Techniques to evaluate weaving on arterial streets, however, are limited. Similar to arterial streets, the traffic operations on frontage or access roads along freeways can also be heavily affected by weaving. Presented here is a technique for evaluating one-sided weaving areas along with recommended lengths of weaving areas. Data from six sites were used to develop a relationship between number of lane changes and weaving volume. The weaving sections at the sites ranged from three to four lanes and from approximately 137 to 335 m in length. Throughout the large range of volumes present (250 to 2,500 vph), there was a very strong relationship between weaving volume and lane changes. The field data were used to develop a computer simulation model. The relationships between different measures of effectiveness from the simulation model provided information on critical points in which the weaving speed begins to drop more rapidly. Weaving volumes (entrance-ramp plus exit-ramp volumes) of less than 1,500 vph are associated with unconstrained levels of service, volumes between 1,500 and 3,000 vph with constrained service, and volumes over 3,000 vph with undesirable service. Additional information from the models also demonstrated that it is desirable to have a weaving length greater than 300 m. If this length is not achievable, then the minimum length should be approximately 200 m.

Evaluating the Capacity of Freeway Weaving Sections

The research described in this paper employed simulation modeling and empirical observations in an effort to (1) Identify the traffic flow phenomena that characterize freeway weaving section capacity; and (2) determine appropriate traffic flow rate values that reflect weaving section capacity. The INTRAS microscopic simulation model was calibrated and validated using empirical data collected at a weaving site. Increasing traffic demands were then sequentially input into repeated simulation runs to identify the boundary between uncongested and congested operation. Where a weaving section exhibits a typical level of both merging and diverging traffic movements, capacity is defined as a function of flows and lane-changing rates occurring in the vicinity of the weaving area’s merge gore. Where a weaving section operates with a relatively low total weaving demand, capacity is defined as a maximum rate of vehicles per lane. Validation experiments described in this paper suggest that the derived values of capacity apply to any one-sided freeway weaving section.