Dynamic Lane Research Articles

Evaluating Variable Speed Limits and Dynamic Lane Merging Systems in Work Zones: A Simulation Study

ITS technologies such as dynamic lane merging (DLM) and variable speed limits (VSL) have been deployed in roadway work zones in an attempt to enhance safety and mobility through vehicular traffic. The DLM system in its two main forms namely the early merge and the late merge was designed to advise drivers on definite merging locations whereas VSL were introduced to work zones to decrease speed fluctuations, variances, and to smoothen traffic through work zones. Up to date, there are no studies that contrast Maintenance Of Traffic (MOTs) plans including a combination of ITS technologies to standard work zones MOTs under matching work zone settings. This study simulates a two-to-one work zone lane closure configuration in VISSIM under six different MOT plans and compares work zone throughputs and travel times across MOTs namely Motorist Awareness System (MAS), early DLM, late DLM, VSL combined with MAS, a VSL and early DLM combination, and a VSL late DLM combination. Results showed that the combination of VSL and DLM or standalone DLM improve work zone throughputs and travel times compared to work zones with conventional static Florida MOT and work zones with VSL.

Traffic Management for Automated Highway Systems Using Model-Based Predictive Control

We present an integrated traffic management and control approach for automated highway systems (AHS). The AHS consist of interacting roadside controllers and intelligent vehicles that are organized in platoons with short intraplatoon distances and larger distances between platoons. All vehicles are assumed to be fully automated, i.e., throttle, braking, and steering commands are determined by an automated onboard controller. The proposed control approach is based on a hierarchical traffic control architecture for AHS, and it also takes the connection and transition between the nonautomated part of the road network and the AHS into account. In particular, we combine dynamic speed limits and lane allocation for the platoons on the AHS highways with access control for the on-ramps using ramp metering, and we propose a model-based predictive control approach to determine optimal speed limits and lane allocations, as well as optimal release times for the platoons at the on-ramps. To illustrate the potential of the proposed traffic control method, we apply it to a simple simulation example.

Comparing Three Lane Merging Schemes for Short-Term Work Zones: A Simulation Study

Traffic safety and mobility of roadway work zones have been considered to be one of the major concerns in highway traffic safety and operations in Florida. Dynamic lane merging (DLM) systems—ITS-based lane management technology—were introduced by several states in an attempt to enhance both safety and mobility of roadway work zones. Two forms of lane merging, namely, the early merge and the late merge were designed to advise drivers on definite merging locations. Up to date, there are no studies that contrast both merging schemes under matching work zone settings. This study simulates a two-to-one work zone lane closure configuration under three different Maintenance of Traffic (MOT) plans in VISSIM. The first MOT is the conventional plans used in Florida’s work zones, the second MOT is a simplified dynamic early merging system (early SDLMS), and the third MOT is a simplified dynamic late merging systems (late SDLMSs). Field data was collected to calibrate and validate the simulation models. Simulation results indicated that overall, under different levels of drivers’ compliance rate and different percentages of trucks in the traffic composition, the early SLDMS outperformed the conventional MOT and the late SDLMS in terms of travel times and throughputs.

Improving Bus Transit in Cities with Appropriate Dynamic Lane Allocating Strategies

This paper describes how dynamic lane allocation strategies may improve bus transit. The considered strategies are bus lanes with intermittent priorities (BLIPs). These strategies consist in intermittently opening the bus lane to general traffic when not in use by a bus. Even if benefits of such strategies have been pointed out in the literature, the activation process has received little attention. Chiabaut et al. (2012) has firstly proposed an analytical approach for BLIPs activation. However, the analytical (extended) kinematic wave model uses a rough description of lane-changing maneuvers. This paper tries to overcome this limitation through a refined approach using the simulation package SymuVia. The simulated results show a good agreement with analytical results. For comparable case, simulation enables more sophisticated case to be investigated. A sensitivity analysis is carried out to identify the parameters that have the most influence on BLIPs activation efficiency.

Dynamic Lane Grouping at Isolated Intersections: Problem Formulation and Performance Analysis

This paper presents some fundamentals of the dynamic lane grouping (DLG) concept, the aim of which is to improve lane utilization under variations in traffic demand. The problem was formulated as a mathematical programming model to determine the optimal lane allocation of an isolated intersection in relation to minimizing the maximum lane flow ratio (defined as the assigned flow divided by the saturation rate). Shared lanes and user equilibrium status for lane use were also considered in the model. Numerical analyses were conducted for four cases with different numbers of lanes, saturation levels, and methods for setting signal timing (adaptive and fixed timing). The results indicated that DLG might provide significant performance improvement in reducing the maximum-flow ratio under the spatial variation in demand. The performance of DLG was also compared with real-time adaptive signal timing by means of the average delay; improvements to the average delay were also observed when the spatial variation was large. The maximum-flow ratio and the average delay of DLG remained almost unchanged for the full spectrum of spatial demand variation when total demand was constant. The results also implied that the more significantly the demand varied, the more benefits the dynamic lane grouping method could potentially provide.

Numerical simulation of a continuum model for bi-directional pedestrian flow

An algorithm for an extended reactive dynamic user equilibrium model of pedestrian counterflow as a continuum is developed. It is based on a cell-centered high-resolution finite volume scheme with a fast sweeping method for an Eikonal-type equation on an orthogonal grid. A high-order total variation diminishing Runge–Kutta method is adopted for the time integration of semi-discrete equations. The numerical results demonstrate the rationality of the model and efficiency of the algorithm. Some crowd pedestrian flow phenomena, such as dynamic lane formation in bi-directional flow, are observed which are helpful for a global comprehension of pedestrian dynamics. Also, the model can be utilized with different potential applications.

Improving Energy Efficiency in IEEE 802.3ba High-Rate Ethernet Optical Links

Energy efficiency in communications, and particularly Ethernet, is becoming an important research area. The IEEE 802.3az energy-efficient Ethernet standard has already proposed a mechanism to reduce energy consumption on copper-based physical layer devices. This mechanism exploits the well-known fact that end-user links are usually lightly loaded, and that important energy savings can be achieved, if the device is put into a low-power sleep-mode whenever no frames are pending for transmission. This study pursues a two-goal purpose: firstly, it aims to evaluate whether such an active/sleep dual-state mode is suitable for high-rate optical Ethernet links as defined in the upcoming IEEE 802.3ba amendment that specifies the lower layers of 40- and 100-Gigabit Ethernet. Secondly it proposes to use an algorithm that dynamically exploits the multilane architecture of the high-speed optical transport layer. As it is studied throughout the paper, the two-state active/sleep-based mechanism may not achieve energy savings, while a load-based dynamic lane management enables energy reductions for a wide range of input traffic loads. A commercially available 100GBASE-SR10 module is used as case study for the analysis.

Safety impact of using the hard shoulder during congested traffic. The case of a managed lane operation on a French urban motorway

Motorway operators deploy dynamic lane management operations to reduce recurrent congestions. The aim of this paper is to contribute to the safety assessment of such an operation which has been introduced on a French urban motorway weaving section. It consists in the opening of an auxiliary lane partly taken on the hard shoulder. The assessment is based on the observational before-after method in road safety, which compares the empirical number of accidents with a prediction of the number of those which would have occurred, had no change happened. A comparison site is used to identify the trend on the number of accidents between the before and after periods, independently of the effect of the operation. A variant of this method, which takes into account the traffic regimes, is developed here. This variant removes some bias, which may exist when the traffic patterns on the comparison site and on the assessed site are different. We highlight here how critical is the choice of the comparison site; how significant is the correlation between the risks of accidents by type and the traffic regimes, because that correlation, if changing over time, induces a bias; how meaningful is the provided analytic expression of the bias. Although inconclusive – due to the small number of recorded accidents – concerning the final safety impact of the operation, the main questions are discussed - reduction in traffic density leading to a reduction in the number of accidents, migration of traffic towards the opening hours, migration of density and accidents downstream. This contributes to a better understanding of the evolution of traffic safety and of the safety impact of the lane management operation.

Operational Evaluation of Dynamic Lane Merging In Work Zones with Variable Speed Limits

Intelligent Transportation System (ITS) technology has been developed to improve the safety and mobility of traffic in and around work zones. In several states in the US, use of Dynamic Lane Merge (DLM) system has been initiated to enhance traffic safety and smooth traffic operations in work zone areas. The DLM usually takes two forms; dynamic early merge and dynamic late merge. The use of variable speed limit (VSL) systems at work zones is also one of those measures. It is anticipated that the VSL systems improve safety by helping the driver in determining maximum speed that he or she should travel. Besides adding improvement to safety, they are also expected to improve mobility at the work zones.The main goal of this paper is to report on an evaluation of operational effectiveness of the DLMS systems i.e. the Dynamic Early Lane Merge and Dynamic Late Lane Merge, in presence of a VSL system. More specifically, the VISSIM model was utilized to simulate a 2-to-1 work zone configurations for six scenarios namely: Work Zone without VSL and without DLMS, Work Zone with VSL and without DLMS, Work Zone with VSL and Early DLMS, and Work Zone with VSL and Late DLMS, Zone with Early DLMS and without VSL and Zone without VSL and with Late DLMS. Assessment of the effectiveness of these scenarios in terms of throughput to various traffic demands and motorists’ adherence level were conducted.It was found through the simulation of above mentioned scenarios that for low and medium demand volume levels (V0500, V1000 and V1500), that there is no significant difference between the Maintenance of Traffic (MOT) plans for mean throughputs. However, for higher demand volume levels (V2000 and V2500), late SDLMS with and without VSL produced higher mean throughputs for all compliance rates and truck percentages except when the demand volume was 2,500 vph and compliance of 60%, where it produces the significantly lower mean throughputs. © 2011 Published by Elsevier Ltd.

Maneuvers of motorcycles in queues at signalized intersections

AbstractThe maneuvering models of motorcycles in previous studies often considered motorcycles' traveling in terms of movements in a physical static lane and not in terms of dynamic virtual lane‐based movements. For that reason, these models are not able to imitate motorcyclists' behavior well. This paper proposes a maneuverability model framework for motorcycles in queues at signalized intersections with considering the dynamic motorcycle's lane. The model includes (i) a dynamic motorcycle's lane to identify the current, left, and right lanes of the subject motorcycle, (ii) a threshold distance to determine when a motorcyclist starts to consider maneuvering, (iii) a lane selection model to identify the lane preferred by a motorcyclist, and (iv) a gap acceptance model to describe whether or not the lead and lag gaps are acceptable for maneuvering. The model framework captures the variation across the motorcyclist population and over time observations. The models were applied to Hanoi and Hochiminh city, Vietnam, based on microscopic data collected from video images. All of the parameters were estimated using the maximum likelihood method with the statistical estimation software GAUSS. The results show that 77.88% of the observed maneuvers – either staying in the current lane or turning left or right – could be modeled correctly by the proposed models. Copyright © 2010 John Wiley & Sons, Ltd.

Evaluation of Pictograms in Dynamic Lane Control Systems in the Republic of Korea

Pictograms have increasingly been used in electronic message display boards around the world as part of the intelligent transportation systems because they provide drivers with a clear and precise message that is easy to understand. This article reports on an evaluation of pictograms for a dynamic traffic control system in Seoul, Republic of Korea. In this study, some of the pictograms developed in an earlier study were redesigned and transferred to an actual variable message sign for a field test. In addition, drivers' perceptions of these pictograms were also elicited from a convenient sample to provide useful information to assist in the final selection of the pictograms. The study found that most of the pictograms were quite easy to comprehend. However, pictograms depicting accidents performed poorly, with only 10.0% and 43.5% of the participants correctly identifying the message conveyed by the European design and the existing ROK design, respectively. The pictograms depicting congestion and traffic incidents also performed moderately, with only 45%–55% correctly identifying the message conveyed. Finally, the European design for snow warning performed poorly (17.5% correct), whereas the ROK design performed relatively well (75.5% correct).

Scalable Parallel Interface for Terabit LAN

We propose a scalable parallel interface that provides an ideal aggregated bandwidth link for an application. The scalable parallel interface uses time information to align packets and allows dynamic lane and/or path change, a large difference in transmission delays among lanes, and so on. The basic performance of the scalable parallel interface in 10Gb/s x 2 lanes is verified using an estimation board that is newly developed to evaluate the basic functions used in a Terabit LAN. The evaluation shows that the scalable parallel interface achieves a very low delay variation that is almost the same as that under back-to-back conditions. The difference in the delay variation between the scalable parallel interface and the back-to-back condition is approximately 10ns when the transmission delay time varies from 10 μs to 1 s.

Efficiency Consequences of Dynamic Traffic Lanes within Hard Shoulders in Urban Freeways

Efficiency Consequences of Dynamic Traffic Lanes within Hard Shoulders in Urban Freeways

Effects of Heterogeneity on Self-Organized Pedestrian Flows

This investigation focuses on how the heterogeneity of pedestrian characteristics influences the buildup of congestion and affects the efficiency of pedestrian flows. Three commonly used parameters in pedestrian models–-desired speed, body size, and reaction time–-were varied in the population. Real pedestrian flows are heterogeneous regarding pedestrian characteristics. However, not much is known about the way that affects the qualities of the flow and how important it is to the outcomes of microsimulation models. The NOMAD model developed by Delft University of Technology is used to perform simulations in which the aforementioned heterogeneity is introduced. The investigation was carried out by creating bidirectional flows with fixed demands. The flows were analyzed by observing the development of breakdowns, average speeds, and average densities for different demands. It is shown that the influence of heterogeneity on breakdown probabilities and flow efficiency is considerable. To investigate this further, the dynamic lane formation process is investigated in detail. In addition to further insights into the causes for breakdown, it is found that the number of lanes increases with the decrease in heterogeneity in desired speed and in body size. However the opposite happens for heterogeneity in reaction time. Results indicate that heterogeneity in the population has a large impact on the flow quality and should be included in models explicitly to improve prediction performance.

The toll plaza optimization problem: Design, operations, and strategies

This paper presents comprehensive decision-making procedures for designing a new toll plaza with the right initial capacity, then finding the optimal dynamic lane configuration for operations, evaluating the effects of increasing future traffic volume on waiting time by sensitivity analysis, and establishing a long-term quantitative strategy by transferring low-throughput lane users to high-throughput lanes. We develop a non-linear integer programming model integrated with the M/ G/1 queueing process. A case study based on actual data demonstrates how effective the model and the strategy are in reducing operating and user-waiting costs and, thus, improving overall system performance at toll plazas.

Dynamic Late Lane Merge System at Freeway Construction Work Zones

In normal work zones with lane closures, drivers do not merge at any one definite point, a situation thus often causing a sudden interruption in traffic flow and sometimes higher delay and longer queue. The Dynamic Late Lane Merge System (DLLMS) is used to specify a definite merge point, improve the flow of congested work zones, and reduce queue lengths in travel lanes. The DLLMS was implemented in Michigan on three freeway segments that were reduced from two lanes to one lane because of highway construction work zones. The DLLMS directed traffic to use both lanes (open and closed lanes) until the designated “merge point” (close to the taper) where traffic from each lane was instructed to take turns merging into the open lane. On the basis of travel time characteristics, merge locations, and throughput, the effectiveness of the DLLMS was evaluated as a part of this study. The before period data were not available; therefore, a conventional work zone merge system, located on eastbound I-94, was used as a control site for the westbound I-94 test site. Comparison of the I-94 control and test sites indicated that the presence of the DLLMS improved the flow of travel and increased the percentage of vehicles that merged at or near the designated taper location. Based on the expected travel time savings, at a $5/h value of time, the benefit-cost ratio will be greater than 1, indicating that the monetary benefits of the DLLMS outweigh the cost of the system.

Minnesota's Proposal for Urban Partnership Agreement

In 2007 Minnesota was one of five finalists for an Urban Partnership Agreement (UPA) grant through a unique competition initiated by the U.S. Department of Transportation (USDOT). Minnesota was awarded a $133-million UPA grant by the USDOT to use congestion pricing in combination with other strategies to reduce congestion in a major transportation corridor. In 2005 Minnesota had previously adapted a high-occupancy vehicle lane to a high-occupancy toll (HOT) lane on I-394 west of downtown Minneapolis. These HOT lanes are known as MnPASS lanes. The UPA project will extend the MnPASS lanes to I-35W south of Minneapolis, the most heavily traveled stretch of urban Interstate in the Minneapolis–St. Paul metropolitan area. The proposal includes the use of priced dynamic shoulder lanes to make more efficient use of existing capacity as well as improved transit, telecommuting, and technology support in the corridor and in downtown Minneapolis. The significant federal dollar commitment to funding UPA projects, particularly through transit funding, has played a key role in generating political and institutional dialogue and support, especially among local government elected officials and legislators in the I-35W corridor. Stakeholder workshops have been an important outreach and education mechanism to inform and engage elected officials and other key constituents during the UPA application process.

BRAESS'S PARADOXES IN DYNAMIC TRAFFIC ASSIGNMENT WITH SIMULTANEOUS DEPARTURE TIME AND ROUTE CHOICES

In this paper, we investigate some new dynamic phenomena of Braess's paradox in transportation networks when both the departure time and route choices are considered simultaneously. The classical Wardropian user equilibrium principle is used to characterize route choice behavior, and the traditional bottleneck models with deterministic queues are employed to describe user's departure time choice behavior. New Braess's paradoxes with dynamic user response have been found in respect to the point queue and physical queue assumptions, and the mechanisms of such paradoxes are analyzed in details. Furthermore, it is shown in a numerical example that a paradox may occur in network when physical queue assumption is made, but the paradox may not be found in network if the point queue assumption is adopted in the proposed dynamic traffic assignment model. Due to the significant difference between point queue and physical queue assumptions, spatial dimension of queues has to be considered carefully in dynamic traffic assignment models. Finally, some traffic management measures are suggested and examined to resolve the potential paradoxes, such as link closing, ramp metering, dynamic road pricing, lane partitioning, and adaptive traffic control etc.

Intermittent and Dynamic Transit Lanes

Segregated transit lanes are an efficient means of improving transit reliability and speed on shared urban roads. A major limitation of these lanes, however, is their impact on road capacity and traffic congestion. Intermittent bus lanes (IBL) are an innovative concept for addressing this limitation. IBLs include variable message signs and flashing lights embedded in the pavement that warn motorists to avoid transit lanes only when buses are coming. This approach prioritizes transit while limiting impacts on other road users. If feasible, this approach may substantially increase the scope of transit priority in cities. However, feasibility of IBL is a major concern. A trial was undertaken in Lisbon, Portugal, in 2005 and 2006. Although the results were promising, more practical experience with IBL is required to justify its widespread implementation. This paper reviews the performance of a variation on the IBL concept, the dynamic fairway (DF) adopted for trams in Melbourne, Australia. The system was initiated in 2001 and is still operational. The paper documents the world's first practical, ongoing experience with IBL-DF operation. Future plans for a Melbourne bus-based IBL called the “moving bus lane” are also presented. Overall, the performance of the Lisbon IBL trial appears to be better than that of the Melbourne DF. However, the circumstances of the two examples were different, including the road configuration, transit mode, levels of congestion, and the newness of the technologies involved. Significantly, both applications found good driver compliance with transit lanes, suggesting the IBL-DF concept has practical performance benefits.

Nonlocal Continuous-Space Microscopic Simulation of Pedestrian Flows with Local Choice Behavior

Compared with vehicular traffic, pedestrian flow operations are very complex. This is why vehicular flow simulation modeling approaches are generally not applicable to the description of pedestrian flows. Gaining insights into pedestrian flow operations is important in, for instance, the planning and geometric design of pedestrian infrastructural facilities. Additionally, management of pedestrian flows requires knowledge of pedestrian flow behavior. Motivated by the need for accurate pedestrian flow models, a microscopic pedestrian flow model is presented. The model is characterized by pedestrian interaction behavior, based on stimulus-response mechanisms. Moreover, local route-choice behavior is included, which describes how pedestrians choose their direction on the basis of, among other things, their destination and local pedestrian flow conditions. The choice behavior is based on the concept of subjective utility maximization. Moreover, the model features parallel updating, comparable with recently developed cellular automata models for pedestrian flows. However, contrary to these models, pedestrian locations are not bounded to discrete cells. The model can therefore easily describe multidirectional pedestrian flows (e.g., unidirectional, bidirectional, and crossing). Application of the model to a simple hallway is discussed. Besides speed-density relations, self-organizing phenomena are studied in pedestrian flows (dynamic lane formation and clustering) from the microscopic pedestrian flow model.