Dazhi Sun

Multiobjective traffic signal timing optimization using non-dominated sorting genetic algorithm

The purpose of this paper is to investigate the application of non-dominated sorting genetic algorithm in solving the multiobjective signal timing optimization problem (MOSTOP). Three n-objective signal timing optimization problems with m-constraint, which cover both deterministic and stochastic traffic patterns, are defined and solved in this study. Mathematical approximations of the resulting Pareto Frontiers are presented to evaluate the trade-off among various objectives and thus provide the most appropriate alternatives for all potential situations of the intersection traffic signal design.

Multi-objective traffic signal timing optimization using non-dominated sorting genetic algorithm II

This paper presents the application of Non- dominated Sorting Genetic Algorithm II (NSGA II) in solving multiple-objective signal timing optimization problem (MOSTOP). Some recent researches on intersection signal timing design optimization and multi-objective evolutionary algorithms are summarized. NSGA II, which can find more of the Pareto Frontiers and maintain the diversity of the population, is applied to solve three signal timing optimization problems with 2-objective and 3-constraint, which account for both deterministic and stochastic traffic patterns. Mathematical approximation of the resulting Pareto Frontiers are developed to provide more insight into the trade-off between different objectives. GAs experimental design and result analysis are presented with some recommendations for prospective applications.

A simulation study of using active traffic management strategies on congested freeways

The main objective of this study is to evaluate the effectiveness of using active traffic management (ATM) strategies on freeways in terms of the driver’s behavior and operational impacts. A few test beds were selected to evaluate the impacts of ATM such as speed harmonization, shoulder utilization, and ramp metering. Test beds used in this study were at places where an ATM is either proposed or previously implemented, i.e., where data exists for conditions prior to and after the implementation of ATM. Data collected from the test beds were used in a simulation model to evaluate the impacts of each ATM strategy on speed, travel time, and crash rates. Simulation results indicated that the implementation of speed harmonization on US 90 showed a 14% reduction in crashes and a 2%–3% increase in freeway speed; the implementation of hard shoulders on US 90 showed a 39% increase in travel time, 22% increase in freeway capacity and 60% decrease in delays; and the implementation of ramp metering on US 59 between Bissonnet St. and Fondern road showed a decrease of 23 % in freeway travel time, a 14% increase in freeway speed and 11% decrease in accident rates.

In-depth analysis of traffic congestion using computational fluid dynamics (CFD) modeling method

This paper introduces computational fluid dynamics (CFD), a numerical approach widely and successfully used in aerospace engineering, to deal with surface traffic flow related problems. After a brief introduction of the physical and mathematical foundations of CFD, this paper develops CFD implementation methodology for modeling traffic problems such as queue/platoon distribution, shockwave propagation, and prediction of system performance. Some theoretical and practical applications are discussed in this paper to illustrate the implementation methodology. It is found that CFD approach can facilitate a superior insight into the formation and propagation of congestion, thereby supporting more effective methods to alleviate congestion. In addition, CFD approach is found capable of assessing freeway system performance using less ITS detectors, and enhancing the coverage and reliability of a traffic detection system.

A microscopic simulation-based decision support system to develop changeable message sign alternatives

This paper introduces the development of a web-based decision support system, to facilitate human factor studies regarding the use of changeable message signs (CMS). A microscopic traffic simulator VISSIM was used to generate realistic simulation scenarios with various CMS alternatives implemented. A case study for truck mounted changeable message sign on an urban multilane highway for “right lane closure” condition was discussed in detail to illustrate the use of the proposed system.

Is Heavy Vehicle Percentage (HVP) a Necessary Factor for Predicting Highway Work Zone Capacity

The intent of this paper is to demonstrate the heavy vehicle percentage is not a necessary factor for predicting highway work zone capacity. First, based on the analysis of a multiple regression model in previous study, an improved model introduced the concept of passenger car equivalent (PCE) and defined the effect index (EI) for evaluating the importance of different factor affecting the work zone capacity. The smaller EI of heavy vehicle percentage indicated that the heavy vehicle percentage was not the key factor when estimating the work zone capacity. Second, this paper also ran simulations to compare the travel time when the passenger car equivalent volume remained in the same. The results showed only 5% of the difference in the travel time varied with the heavy vehicle percentages. At last, a new model without the input of heavy vehicle percentage was further developed. Its performance had been proven to be better than that recommended in highway capacity manual (HCM).