Download or read book Evaluating Ramp Metering and Variable Speed Limits to Reduce Crash Potential on Congested Freeways Using Micro simulation written by Albinder Singh Dhindsa and published by . This book was released on 2005 with total page 220 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent research at UCF into defining surrogate measures for identifying crash prone conditions on freeways has led to the introduction of several statistical models which can flag such conditions with a good degree of accuracy. Outputs from these models have the potential to be used as real-time safety measures on freeways. They may also act as the basis for the evaluation of several intervention strategies that might help in the mitigation of risk of crashes.

Download or read book Efficient Transportation and Pavement Systems Characterization Mechanisms Simulation and Modeling written by Imad L. Al-Qadi and published by CRC Press. This book was released on 2008-11-01 with total page 924 pages. Available in PDF, EPUB and Kindle. Book excerpt: Internationally, significant attention is given to transport sustainability including planning, design, construction, evaluation, safety and durability of the road system. The 4th International Gulf Conference on Roads: Efficient Transportation and Pavement Systems - Characterization, Mechanisms, Simulation, and Modeling, hosted by the University o

Download or read book Exploring the Potential of Combining Ramp Metering and Variable Speed Limit Strategies for Alleviating Real time Crash Risk on Urban Freeways written by Kirolos Maged Haleem and published by . This book was released on 2007 with total page 389 pages. Available in PDF, EPUB and Kindle. Book excerpt: In summary, Ramp Metering was more beneficial at congested situations, while Variable Speed Limits were more beneficial at free-flow conditions. At conditions approaching congestion, the combination of Ramp Metering and Variable Speed Limits produced the best benefits. These results illustrate the significant potential of ITS strategies to improve the safety and efficiency of urban freeways.

Download or read book Proceedings of the Conference of the Hong Kong Society for Transportation Studies written by Hong Kong Society for Transportation Studies. Conference and published by . This book was released on 2006 with total page 824 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Optimization and Microsimulation of On ramp Metering for Congested Freeways written by Gabriel Clemente Gomes and published by . This book was released on 2004 with total page 546 pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation investigates various aspect of the design and testing of on-ramp metering control systems, including optimization-based control and microscopic freeway modeling. A new technique for generating optimal metering plans is developed. As with most predictive designs, the ramp metering rates are found as the solution to a nonlinear optimization problem. In contrast to previous designs, the new approach 1) produces a globally optimal solution to the nonlinear problem, 2) requires only to solve a single linear program, and 3) allows the enforcement of hard constraints on the on-ramp queue lengths. The price that is paid for these features is that the objective function being minimized is not Total Travel Time, but rather a member of a class of "TTT-like" objective functions. A TTT-like objective function is defined as a linear combination of mainline flows with weights that, similarly to the Total Travel Time cost weights, decrease linearly in time from some initial value to zero at the final time. An example application of the technique shows that the globally optimal metering plan with respect to a TTT-like objective function also performs well in terms of Total Travel Time. A macroscopic analysis of local traffic-responsive ramp metering on a short stretch of freeway, with a single on-ramp and no offramps, is also presented. The study compares the performance of two popular local traffic-responsive ramp metering algorithms: Alinea and Percent-Occupancy, and addresses issues pertaining to parameter tuning and loop-detector placement. The second half of the dissertation describes the construction of a detailed microsimulation model of a stretch of Interstate 210 in Pasadena, CA. The VISSIM microsimulation package was used to create this model. Descriptions of the data gathering and processing procedures, bottleneck identification, network coding, and model calibration are provided. The model is used to test the performance of candidate local traffic-responsive controllers. Questions concerning the relative merits of these controllers, parameter tuning, and loop-detector placement are addressed in the context of the large-scale microscopic model.

Download or read book Evaluation of Variable Speed Limits Using a Genetic Algorithm Approach to Calibrate a VISSIM Model written by Brian Joseph Schaefer and published by . This book was released on 2010 with total page 182 pages. Available in PDF, EPUB and Kindle. Book excerpt: "The variable speed limit (VSL) system has been adopted on more and more roadways across the globe as an engineering tool for controlling traffic flow, particularly during congestion situations. An important and fundamental question raised among traffic engineers is: Are the costs of installing and operating variable speed limits really justified? In order to answer this question, this thesis measures the effectiveness of the VSL system applying the VISSIM microscopic simulation model to a non-recurrent congestion situation. For the analysis, a section of interstate was modeled in VISSIM and calibrated so that the simulated results closely reproduce the observed data collected from traffic detectors. The calibration process is accomplished using a genetic algorithm (GA) programmed in MATLAB. Once the interstate system is calibrated to the static speed limit condition, the VSL system is portrayed on the model by temporarily blocking lanes to measure the effectiveness of VSL during an incident situation. Multiple incident locations and different VSL configurations are tested to investigate various possible forms of reality. The simulated results of with-VSL and without-VSL systems were compared and evaluated. The results show that no significant changes in travel times are observed, but queue lengths and fuel consumption decrease by 10-20% and 3-5% respectively. The speed variances upstream of the incidents also decreased 10-25% depending on location, which in the end may lead to fewer crashes. Before a VSL system is constructed a study should be conducted to determine if the cost of installing and maintaining the system is justified by the benefits. The benefits of a VSL system include a decrease in fuel consumption as well as a decrease in the deviation of speeds, potentially leading to a reduction in crashes. Further studies need to be done to determine exactly how much the number of crashes could potentially be reduced. If a governing authority has the means for a VSL system they could potentially be justified by a reduction in crashes on the roadway, but the breadth of this thesis does not have enough evidence to support the case that there will be a definite reduction in the number of crashes"--Abstract, leaf iii.

Download or read book A Guide for Reducing Speeding Related Crashes written by and published by Transportation Research Board. This book was released on 2009 with total page 149 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Preparations for Field Testing of Combined Variable Speed Advisory VSA and Coordinated Ramp Metering CRM for Freeway Traffic Control written by Xiao-Yun Lu and published by . This book was released on 2014 with total page 278 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Towards an Efficient and Equitable Motorway System Using Ramp Metering and Variable Speed Limits written by Duo Li and published by . This book was released on 2015 with total page 158 pages. Available in PDF, EPUB and Kindle. Book excerpt: Ramp metering (RM) and variable speed limits (VSL) are two important ITS tools aimed at improving the performance of motorway systems. The former improves the traffic flow conditions on motorway by limiting the inflow of vehicles from on-ramps; while the latter harmonizes the traffic flow on a motorway mainline by minimizing the variation in speed of vehicles obeying the VSL display. The main goal of this research is to improve the efficiency and equity performance of motorway systems using RM and VSL control measures. A number of RM and VSL control algorithms are proposed in this thesis to achieve this goal. They are assessed for a critical bottleneck section of Auckland Motorway using micro-simulation software AIMSUN. First of all, two existing RM algorithms are assessed namely: ALINEA and HERO. HERO outperformed ALINEA in terms of efficiency and equity benefits. Then, a logic tree based VSL control algorithm is also assessed. The results revealed that the existing logic tree based VSL algorithm cannot improve significantly mobility performance of motorway systems and is rather rough for the speed control. Two alternative VSL control algorithms are proposed namely: a modified logic tree based controller and a fuzzy logic based controller. Both utilize optimized control logics and detector-controller configurations. The proposed algorithms outperformed the existing one in terms of their mobility benefits. In the next step, an integrated RM and VSL control method is proposed to preserve the traffic flow at bottlenecks close to their capacity and avoid excessive delays at on-ramps. The integrated method shows prospect to improve further efficiency and equity performance of motorway systems than operating the RM and VSL controllers independently. Finally, the relationship between efficiency and equity is investigated using a modified HERO strategy; this is aimed at achieving a balance between efficiency and equity gains from RM control. A combined index is proposed combining Gini coefficient and total travel time into one index, which can serve as an objective function to solve the bi-objective control design problem.

Download or read book Ramp Metering Status in North America written by James Robinson and published by . This book was released on 1989 with total page 28 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Evaluating Outcomes of Raising Speed Limits on High Speed Non freeways written by Timothy J. Gates and published by . This book was released on 2015 with total page 123 pages. Available in PDF, EPUB and Kindle. Book excerpt: The purpose of this research was to assist in determining the potential impacts of implementing a proposed 65 mph speed limit on non-freeways in Michigan. Consideration was given to a broad range of performance measures, including operating speeds, traffic crashes and crash severity, infrastructure costs, fuel consumption, and travel times. Specifically, a prioritization strategy was developed to identify candidate MDOT non-freeway road segments possessing lower safety risks and potential infrastructure costs associated with raising the speed limit from 55 to 65 mph. Ultimately, approximately 747 miles of undivided and 26 miles of divided 55 mph non-freeways were identified as lower risk candidates, representing approximately one-eighth of the MDOT systemwide mileage posted at 55 mph. An economic analysis of the anticipated costs and benefits associated with the proposed speed limit increase was performed for these lower risk candidate segments, in addition to a systemwide estimate. As the travel time savings were expected to outweigh the fuel consumption costs, it was necessary to determine if these net operational benefits outweighed the expected infrastructure upgrade costs and increased crash costs. For roadways possessing horizontal and/or vertical alignments that are not compliant with a 65 mph speed limit, an unfavorable benefit/cost ratio would likely result due to the excessive infrastructure costs incurred during 3R (resurfacing, restoration, rehabilitation) or 4R (reconstruction) projects. Crashes were expected to increase for all implementation scenarios, with a particular increase in the risk of fatal and incapacitating injuries. Due to the substantially large infrastructure costs, application of the 65 mph speed limit is specifically not recommended for non-freeway segments requiring horizontal or vertical realignment to achieve design speed compliance. Even for segments where compliance with the increased design speed is maintained, careful consideration must be given to the potential safety impacts particularly to fatal and injury crashes - that may result after increasing the speed limit.

Download or read book A Framework for Simulating Variable Speed Limit Algorithms in Corsim written by Clark Letter and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: A major problem associated with freeway operations around major cities is congestion occurrence during peak volume periods. Typically, bottlenecks at merging and diverging junctions as well as incidents create a shockwave that propagates upstream. One of the tools currently examined as a way to dampen the shockwave produced by this bottleneck is variable speed limits (VSL). Current micro-simulators do not provide an interface to easily simulate VSLs and evaluate their impact on traffic, thus simulation must be carried out through additional coding. This study creates a test-bed for simulating and evaluating multiple VSL algorithms using the Corridor Simulation (CORSIM) micro-simulator. Three algorithms for VSL control are selected and simulated to evaluate the effectiveness of each algorithm. The roadway used for the simulation is a 13-mile section of I-95 in Miami, Florida. A run-time extension (RTE) interface is built to communicate with the CORSIM simulation and replicate the VSL operations. Different threshold values are tested to evaluate the effectiveness of each algorithm under various settings. It was concluded that all but one of the scenarios tested show an improvement in the average travel speed and total travel time after VSL is implemented. The throughput for most scenarios showed an improvement when observed over the time duration of the congestion. Overall, the volume-based algorithm showed the most improvement in the simulations.

Download or read book Speed Harmonization and Peak period Shoulder Use to Manage Urban Freeway Congestion written by and published by . This book was released on 2009 with total page 130 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Proactive Integrated Control for Relieving Freeway Congestion written by Xu Wang and published by . This book was released on 2015 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active bottlenecks limit traffic flow on freeway corridors. To relieve bottleneck severity, ramp metering (RM), variable speed limit (VSL) and their integration are often implemented to control the on-ramp and mainline input flow. Currently, freeway operation has become proactive based on short-term prediction. Macroscopic traffic flow models are often applied as prediction models in proactive traffic control strategies. Prior to field implementation, the models need to be calibrated and validated carefully to ensure that they represent real-life traffic situations. This study proposes modifications for METANET model to adapt it to the unpredictability of bottleneck activation during peak hours. The modified model is calibrated and verified its improvement of model prediction accuracy from segment-specific parameters. The modified model is validated that it can replicate traffic state evolutions during peak hours and be applicable in proactive traffic control practice. Weaving maneuvers (i.e., intensive lane changes) are a major cause of bottlenecks during high-demand periods. To consider weaving impacts in RM, this study introduces a proactive optimal RM algorithm that uses dynamic weaving capacity at weaving segments. Sensitivities of capacity and capacity drop are applied to dynamically estimate weaving capacity within a macroscopic traffic flow model. The proposed traffic flow model conducts estimation in a model predictive control (MPC) frame-work. The proposed RM algorithm is evaluated in macro-simulation and its effectiveness is enhanced by real-time estimated weaving capacity. The RM control research reveals a need of theoretical methods for weaving capacity estimation. This study then defines a linear optimization problem to solve weaving capacity and then establishes a lane-changing model to constrain the weaving flows. The proposed method is evaluated and analyzed for sensitivity with field data from two weaving segments. The capacity estimates from the proposed model are consistent with those from the HCM 2010 model and with field observations. Moreover, the weaving capacity is sensitive to weaving maneuvers. The proposed method is finally applied to estimate the real-time maximum discharge flow rate; the estimates match field measurements. Next, this study presents a proactive integrated control of RM and VSL, with goals to improve network-wide travel time and traffic flow. By decoupling the traffic prediction and simulation models, the possible control error sources are analyzed. The evaluation reveals the proactive integrated control achieves an amelioration in total time spent (TTS) up to 13.65% and an increase in total travel distance (TTD) up to 3.41%. The isolated and integrated controls benefit the traffic network in different extent under different demand scenarios. In addition, control rate profiles are analyzed in detail and found that RM is activated during slight congestion and the most congested situation to assist VSL. Through the integration, the infrastructure utility is maximized. Speed transition zones are complex when dynamically created and shifted by VSL. This study then attempts to represent speed limit effect and estimate real-time driver compliance at speed transition zones. The field data from two speed transition zones are investigated for temporal and spatial variations of speed and driver compliance using statistical tests. After selecting several key factors from statistical tests, a linear regression is established to rank the contributions of the selected factors and other general factors proposed by previous research. The regression results confirm speed limit value, surrounding traffic speed and existence of activated speed enforcement or education devices contribute more to driver compliance. Finally, this study reports the preliminary VSL test and details its implementation procedure on Whitemud Drive, Edmonton, Canada. DynaTAM-VSL software is designed to realize all necessary functions for VSL filed implementation. The preliminary test is conducted, and the VSL control performance and reliability are evaluated. The results for before-and-after VSL control are finally analyzed in depth. The analysis compares average traffic speed, standard deviation of speed, total travel time and total travel distance. The results from this study confirm that VSL can relieve recurrent traffic congestion.

Download or read book Evaluation and Improvement of the Stratified Ramp Metering Algorithm Through Microscopic Simulation written by Panos G. Michalopoulos and published by . This book was released on 2005 with total page 101 pages. Available in PDF, EPUB and Kindle. Book excerpt: A new ramp metering strategy implemented on the Twin Cities freeway system to reduce ramp waiting times was evaluated through microsimulation of freeway activity. The study compared Stratified Ramp Metering strategy with the previous Zone Metering Strategy and with no control strategy. Comparison with Zone, which was designed to favor freeway flow, showed the new strategy succeeded in greatly reducing ramp delays and lines. When compared to the results of no control strategy, it reduces freeway travel time, increases freeway speed, smoothes the flow of traffic, and reduces the number of stops. However, travel time, fuel consumption and pollutant emissions are unpredictable under the newer system. Compared to no control strategy, such measures of effectiveness may improve or worsen depending on the freeway patterns and demand. Based on these findings, the researchers will seek improvements to the design of the Stratified Ramp Metering algorithm so as to factor in disruptive traffic patterns.

Download or read book Examining Dynamic Variable Speed Limit Strategies for the Reduction of Real time Crash Risk on Freeways written by Ryan J. Cunningham and published by . This book was released on 2007 with total page 231 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the free-flow condition (60% loading), the best treatments involved the more liberal threshold for defining homogeneous speed zones (5 mph) and the more liberal implementation distance (entire speed zone), as well as a minimum time period of 10 minutes. This treatment was actually shown to significantly reduce the network travel time by 0.8%. It was also shown that this particular implementation strategy (lowering upstream, raising downstream) is wholly resistant to the effects of crash migration in the 60% loading scenario. In the condition approaching congestion (80% loading), the best treatment again involved the more liberal threshold for homogeneous speed zones (5 mph), yet the more conservative implementation distance (half the speed zone), along with a minimum time period of 5 minutes. This particular treatment arose as the best due to its unique capability to resist the increasing effects of crash migration in the 80% loading scenario. It was shown that the treatments implementing over half the speed zone were more robust against crash migration than other treatments. The best treatment exemplified the greatest benefit in reduced sections and the greatest resistance to crash migration in other sections. In the 80% loading scenario, the best treatment increased the network travel time by less than 0.4%, which is deemed acceptable. No treatment was found to successfully reduce the rear-end and lane-change crash risks in the congested traffic condition (90% loading). This is attributed to the fact that, in the congested state, the speed of vehicles is subject to the surrounding traffic conditions and not to the posted speed limit. Therefore, changing the posted speed limit does not affect the speed of vehicles in a desirable manner. These conclusions agree with Dilmore (2005).

Download or read book Evaluation of Mobility Impacts of Temporary Ramp Metering in Work Zones written by Naghma Hassan and published by . This book was released on 2012 with total page 170 pages. Available in PDF, EPUB and Kindle. Book excerpt: Road maintenance has been growing in the United States and brings a variety of challenges to the transportation profession. Work zone congestion is one of the most important factors contributing to the delay and safety of freeways. Many control methodologies have been applied to work zones in order to reduce freeway congestion and delay. One means of control is ramp metering, which has been deployed since 1963 in the United States and has proven to be successful. This thesis' objective is to evaluate and simulate the effect of ramp metering on freeway work zones; traffic performance measures such as delay, speed, and number of stops are used for the evaluation. A literature review showed that a main factor contributing to the freeway work zone delay is a high percentage of commercial trucks. Due to the role of truck percentage in work zone performance, effectiveness of ramp metering in work zone control is evaluated with different truck percentages. The lane configuration for all the studied sites work zones was 2 lanes to 1 lane, because it's frequency in real-world applications. In the evaluation of ramp metering in work zones, the traffic volumes investigated were less than, equal to, and more than capacity (650vph, 1240vph, and 1854vph). Mainline (a link used for trough traffic) truck percentage and ramp truck percentage varied from 10% to 40%, and 10% to 20%, respectively. As a result, a total of 8 cases were created and simulated using VISSIM traffic simulation software.