Ramp-metering Control Research Articles

Two-class emission traffic control for freeway systems

In the paper a traffic control strategy based on ramp metering is proposed in order to reduce traffic emissions in freeway stretches. Such strategy is devised to take into account that two vehicle classes are present in the freeway (cars and trucks) and that they are separately controlled. The simulation analysis developed in the paper shows, first of all, that the proposed control strategy is able not only to reduce traffic emissions in the freeway but also to reduce the congestion, by decreasing the total time spent by vehicles in the system. Moreover, the effectiveness of the two-class ramp metering control is shown on different traffic scenarios, that are deeply analysed and discussed in the paper.

Off-Ramp Control near Surface Road

To enhance the overall performance of operation of urban expressway, a ramp metering control strategy is proposed to delays and queues of vehicle platoon along off-ramp near the surface road. This control mode measures the real time traffic conditions at off ramps through the derived occupancy data and then optimizes the green time and length of cycle. A Vissim based simulation analysis is used to verify the effectiveness of this proposed control strategy using the field data of Zhuque Bridge and Taoyuan Bridge of South 2 Ring Road in Xi’an city. The simulation results show that the traffic flows can be allocated homogeneously, even during the peak hours and the average traveling time and platoon queue can be reduced approximate 5~7%, compared with the simulated findings of no control mode and fixed time control mode.

Development of Ramp Metering Using Fuzzy Logic Control Algorithm on Freeway

Ramp metering can effect on mitigating the traffic congestion on freeway. In Taiwan, the conventional Local Traffic Responsive (LTR) ramp metering model based on the capacity and demand algorithm has been adopted for freeway ramp control since long time. For enhancing the ramp metering technology, this paper aimed at developing a new Fuzzy Logic Control (FLC) algorithm based on the real traffic situation for ramp metering control on the highway tunnel, by taking Freeway No.5 as the case, which is a freeway with the longest tunnel of 12.9km, in order to enhance the ramp metering performance on relieving traffic congestion. Through the comparative analysis using microscopic simulation, the FLC ramp metering results in higher performance on mitigating the congestion than the LTR control and no control.

Multi-class local ramp metering to reduce traffic emissions in freeway systems

In this paper a local ramp-metering strategy is proposed to minimize traffic emissions in a freeway; the control scheme is based on a two-class dynamic model in which two vehicle categories related to cars and trucks are explicitly represented. In fact, a major objective of the proposed approach is to devise separate ramp metering control actions for the two classes of vehicles, supposing that separate lanes at the on-ramps and separate traffic lights are present for fast vehicles and slow vehicles. In order to take explicitly into account the traffic emissions of vehicles, we adopt an average-speed model, according to which the emission factor for a given pollutant depends on the average speed during a trip. Considering such a model, a desired value of the traffic density for each class of vehicles is fixed and a properly adapted PI-ALINEA strategy is proposed. The experimental tests show the effectiveness of the proposed approach.

Comparative analysis of probe‐based ramp metering with detector‐based and pretimed ramp metering

SUMMARYIn this paper, a probe‐based adaptive ramp metering approach has been developed and compared with a detector‐based and pretimed ramp metering approaches using PARAMICS microsimulation model made by Quadstone Limited. Both examined probe‐based and detector‐based ramp metering approaches adopt the same problem formulation; however, they differ by the data source that provides estimates of their input parameters. The probe‐based approach takes as main input space mean speed extracted from vehicle probes moving constantly on the entire freeway. The detector‐based approach takes the density readings directly from point detectors placed upstream and downstream of each on‐ramp. The developed approach formulates the ramp metering rates to simultaneously reduce freeway travel time and decrease delays on ramps. A dynamic weighting scheme is adopted in this formulation to give different weighting schemes to the various freeway sections and the on‐ramps. These weights are able to adjust dynamically based on prevailing and forecasted traffic conditions to give priority in each step to the sections of the freeways or/and on‐ramps experiencing critical traffic conditions. The comparative analysis of the three ramp metering approaches was conducted on an 8‐km freeway section on Highway 2 in Calgary, Alberta, Canada. The results of the analysis indicate that the probe‐based algorithm consistently outperformed the two other approaches in terms of all performance measures. The probe‐based approach is shown to exceed the performance of the detector‐based approach with a market share of vehicle probes as low as 3%. The results of the analysis are promising and show the effectiveness of developing ramp metering control algorithms taking the main input parameters from vehicle probes on the freeway. Copyright © 2012 John Wiley & Sons, Ltd.

Microsimulation Model for Motorway Merges With Ramp-Metering Controls

This paper presents a newly developed microsimulation model for motorway merge traffic, focusing on issues that relate to ramp-metering (RM) control and its effectiveness. The model deals with general and more specific drivers' behavioral tasks, such as the drivers' cooperative nature in allowing other drivers to merge in front of them either by decelerating or shifting to adjacent lanes. The main criteria of this model are governed by the application of car-following, lane-changing, and gap-acceptance rules. The model has been calibrated and validated mainly using real traffic data taken from loop detectors for two-, three-, and four-lane motorways. Compared with the S-PARAMICS software, using the same data, the model showed better results. The effectiveness of some of the widely used RM control algorithms, such as Demand-Capacity, ALINEA, and ANCONA, were also assessed after finding the optimum parameters (such as critical occupancy and position of loop detectors).

Multicriteria ramp metering control considering environmental and traffic aspects

In this paper a multicriteria ramp metering control is designed considering three criteria: traffic performance and the local– and global effects of traffic emission. For real-time emission modeling a macroscopic modeling framework is proposed using an average-speed emission model. Based on the proposed model function cost functions regarding the global and local effects of traffic emission are stated. Traffic control is realized via ramp metering and the control input is optimized by using the NMPC technique. The closed-loop simulation of the designed control is carried out in VISSIM microscopic simulator.

A simulation-based methodology to compare the performance of highway space inventory control and ramp metering control

The Highway Space Inventory Control System (HSICS) is a novel travel demand management concept in which all road users have to make reservations in advance to enter a highway. A modeling framework for such a system is proposed and illustrated for a hypothetical highway section. The proposed system allocates highway space temporally and spatially over time so as to optimize highway utilization by maximizing passenger miles traveled. In this paper, a methodology is developed to perform a quantitative comparison of the operational performance of HSICS and two isolated ramp metering techniques: the ALINEA algorithm and fixed pre-timed metering. The methodology involves a combination of microscopic traffic simulation and heuristic optimization. The proposed framework is generic and can be applied to compare other traffic control and demand management techniques. The proposed methodology is tested on a simulated highway section with traffic and geometric characteristics similar to a real congested site. Simulation results show that HSICS produces approximately 35 and 45% more passenger miles than ALINEA and fixed pre-timed metering, respectively. Vehicle miles traveled values for HSICS are comparable to those of ALINEA − 4% lower.

Ramp Metering Research of Junction Based on Fuzzy Neural Network Model

On relieving the growing serious urban traffic congestions, the problem of designing fuzzy control strategies for periphery networks that include freeway and related urban expressway(abbreviations: junction) is considered starting with the analysis on impact factors about ramp metering control. The presented novel methodology based on the fuzzy control and neural networks modeling paradigm whose input variables are the differentials between mainline real condition and expected condition and the ramp condition and output variables is the ramp control metering law. Based on the strategy, combining with space structure analysis of interchange in real world, the control metering method for single ramp and coordinated double ramps control metering is presented respectively and the corresponding 5 layer Fuzzy Neural Network (FNN) model is also built. A preliminary simulation-based investigation of the ramp metering control problem for periphery networks consists of G2 freeway, the 3th and 4th ring road using the methodology demonstrates the comparative efficiency.

Sequential Modeling Framework for Optimal Sensor Placement for Multiple Intelligent Transportation System Applications

Traffic sensors have been deployed for decades to freeways to meet the requirements of various traffic/transportation applications, most noticeably traffic control and traveler information applications. A unique feature of traffic sensor deployment is that it is a continuous and evolving process. That is, with new applications that emerge, additional sensors are usually required to be deployed to meet new requirements. This process is also sequential in nature and the new deployment has to consider existing sensors. In this paper, we propose a modeling framework to capture this sequential decision-making process for traffic sensor deployment. The framework is based on our recent findings that (1) optimal sensor deployment for a single application can be determined by a staged process or, more formally, a dynamic programming (DP) method and (2) new sensor locations for new applications can be optimally solved by the DP method via considering existing sensors. We illustrate the framework using two applications: ramp metering control and travel time estimation. It is found that the proposed scheme can appropriately capture the decision-making process of traffic sensor deployment and can generate optimal sensor placement at any stage by considering sensors that have already been deployed. The model is tested using global positioning system enabled cell phone data and traffic simulation on a real-world freeway route in the San Francisco Bay Area.

System Dynamics And Feedback Control Design Problem Formulations For Real Time Ramp Metering

This paper formulates the ramp metering control problem as a real-time feedback control problem. The development is shown by modeling freeway sections, and hence the results are immediately applica...

Coordination Concepts for Ramp Metering Control in a Freeway Network

The steadily increasing numbers and lengths of traffic jams on freeways have led to the application of Dynamic Traffic Management (DTM) measures all over the world. Ramp metering control has proven to be one of the most efficient means to reduce freeway congestion. Currently, it is expected that integrated and coordinated application of DTM measures will further improve its impact. This paper studies a coordinated ramp metering control algorithm called HERO/RWS. This algorithm has been developed for the current Dutch ramp metering systems and it will be applied on the Amsterdam A10 freeway network in the near future. The aim of this algorithm is to postpone congestion on freeways by effectively using ramp storage space from upstream on-ramps. VISSIM-based microscopic simulation results show that the HERO/RWS coordinated control outperforms non-coordinated ramp metering control. Parameter settings have been optimized for the specific A10-west network through a robustness study. In addition, the concept of coordination between ramp meter and upstream intersection traffic controllers is developed. The feasibility of this idea has been proven by a simulation study.

State dependent ramp metering control of motorway bottlenecks using non-linear pole assignment

Ramp Metering (RM) utilises traffic lights at the on-ramp entrances to limit access to the main carriageway of the motorway, in order to maintain flow close to capacity. In comparison to linear design, adaptive or predictive control systems can offer improved performance, albeit with the disadvantage of increased complexity, which can be prohibitive in the context of RM. By contrast, the present article develops a state dependent parameter (SDP) approach to traffic modelling and an associated non-linear pole assignment RM algorithm that is relatively straightforward to implement. Although the SDP model describes occupancy, its parameters are functionally dependent on other variables in the system, such as average velocity. In this manner, SDP models capture the time varying and non-linear dynamics of motorway flows but can, nonetheless, be estimated off-line. The paper illustrates the approach using telemetered measurements from near Southampton in the UK. Algebraic solutions to the control problem are similarly derived off-line and evaluated on-line using a macroscopic simulation model.

Coordination of Ramp Metering and Variable Speed Limits

Abstract In Kamel et al. (2009), we have proposed a local ramp metering control algorithm to reduce the congestion and consequently the total time spent by the vehicles in the network. In this paper, we extend this control algorithm and propose a control approach for the coordination of ramp metering and variable speed limits. In order to evaluate the controller's efficiency and applicability, a comparison is made with the ramp metering only case and the results related to the Genetic-Fuzzy Control Application to Ramp Metering and Variable Speed Limit Control considered in Ghods et al. (2007). The macroscopic traffic model METANET and its extension for dynamic speed limits are used to present the simulation results. We conclude that the proposed coordination of ramp metering and speed limits approach improve the performance of the freeway traffic network.

OPTIMIZATION OF DYNAMIC RAMP METERING CONTROL WITH SIMULTANEOUS PERTURBATION STOCHASTIC APPROXIMATION

Congestion is always a serious problem in many transportation commuting corridors. The need to implement effective control in the corridors has long been recognized by transportation professionals. Ramp metering has been discussed as a viable control strategy on freeways in many places of the US, which may alleviate or at least reduce the delay. In this study, a dynamic ramp metering control model is developed to maximize the total throughput with simultaneous perturbation stochastic approximation (SPSA), subject to the constraints of link densities, capacities, and feasible range of metering rates. A case study for a segment of US I-80 in New Jersey is conducted, while the impact of the proposed ramp metering control on traffic behavior is simulated with CORSIM.

Overview of Traffic Signal Operation Policies for Ramp Metering

A ramp metering control algorithm includes typically two distinct components: the (most important) control strategy, which makes real-time decisions on the ramp exit flow to be implemented, and the translation of this decision into specific traffic light settings according to the applied metering policy. This study focuses on the second component, providing an overview of practiced metering policies (one car per green, n cars per green, full cycle, and discrete release rates) along with a discussion of their advantages and shortcomings. Further related issues, such as traffic signals, multiple metering lanes, bypass lanes, check-in and check-out detectors, integration of both control components, and on–off switching logic, are also addressed.

Urban Expressway-Arterial Corridor On-Line Control System Based on Advanced Traveler Information System

A novel on-line dynamic traffic control strategy for an urban expressway-arterial corridor system is proposed. The corridor system comprises an expressway mainline, on and off-ramps, and surface streets (arterial roads). The ramps are not subjected to any ramp metering control. Assuming that the real-time vehicle arrival and departure can be obtained from the loop detectors on the expressway, the proposed traffic control strategy aims to maintain a predetermined level of service on a congested expressway section by disseminating the congestion information to drivers through various advanced traveler information system means. This strategy consists of three components: expressway mainline control (EMC), on-ramp control (OnC), and off-ramp control (OffC) mechanisms. The EMC mechanism is the major component that diverts vehicles from the expressway to the surface streets, and the OnC and OffC procedures protect the ramps and surface streets from excessive flow. This is because diverting the vehicles without taking into consideration the surface street capacity may cause the overall performance of the corridor system to deteriorate. A simulation-based modeling methodology is developed to evaluate the on-line dynamic traffic control strategy. The evaluation is carried out by performing sensitivity analysis tests of the control parameters used in the strategy. A case study based on a corridor system in Singapore has shown that the traffic control strategy is effective.

Evaluation of Effects of Ramp Metering on Merging Operations

Merging on motorways represents one of the most difficult and dynamic maneuvers of all driving subtasks. Merging operations at uncontrolled ramp junctions have been extensively investigated. With the rapid implementation of ramp metering techniques, many junctions are now operated under ramp metering control. Little research has been done to investigate the possible effects of ramp metering on the merging operation. The research described in this paper focuses on the comparisons of merging operations under both metered and unmetered scenarios. Time series data of the merging process were collected with the Transportation Research Group instrumented vehicle and video cameras at a tapered motorway merge site. The data included accurate vehicle speed measured by laser speedometer, leading and following headway measured by radar, and driver's eye movement derived from an in-car camera. Following a comprehensive analysis of the data, it was found that merging operations under ramp control could be significantly different from free merging. Merging maneuvers may become more difficult as a result of ramp control. The equity implications of such effects are discussed. It is believed that the understanding gained from this research will be useful for the design and operation of ramp metering.

Lyapunov stability analysis of networks of scalar conservation laws

It is shown how an entropy-based Lyapunov function can be used for the stability analysis of equilibria in networks of scalar conservation laws. The analysis gives a sufficient stability condition which is weaker than the condition which was previously known in the literature. Various extensions and generalisations are briefly discussed. The approach is illustrated with an application to ramp-metering control of road traffic networks.

A detailed evaluation of ramp metering impacts on driver behaviour

Ramp metering was first installed in Chicago in 1963 and is now widely employed in North America and European countries to alleviate motorway traffic congestion. A detailed investigation was carried out to study the potential impacts of ramp metering on driving behaviour. An instrumented vehicle and 11 video cameras were used to measure detailed driving performance of drivers merging at on ramps and those on motorway carriageways in a ramp metering controlled intersection with and without ramp metering control. The main behavioural parameters used for the study include: speed, headway, acceleration and deceleration, sizes of accepted gap, merge distance, speed at merge, etc. Based on the study, it is believed that ramp metering does result in driving behaviour changes of traffic on the motorway carriageway and on ramp. It improves the merge condition of traffic at the on ramp, but may cause minor reduction of speeds of traffic on motorway carriageway during the metering time.