Journal of Transportation Engineering
Year:2012 | Volume:3 | Issue:3 (11)|Papers Count:8

Traffic congestion is said to be a major trouble in most of the world’s cities. Delays, degradation of environmental quality, and nonrenewable energy consumption are some outcomes of traffic congestion. Discontent about traffic congestion usually inclines policymakers to propose solutions to reduce it. Studies have shown that there is a difference between the responses to congestion that are assumed by policymakers and those that individuals adopt. Although such solutions serve social causes, individuals are often looking for a solution to solve their own problems. Many studies have shown that there is a difference between the responses to congestion that are assumed by policymakers and those that are actually adopted by individuals. This paper adopts a behavioral approach to examine the mentioned difference using design of experiments principles and Logit models. In this approach, five policies namely cordon pricing, parking pricing, increasing fuel cost, transit time reduction, and transit access time reduction were investigated. Based on levels of coerciveness, effective policies for attracting car commuters to each of the existing non-car modes and their contributions to individuals’ mode change were taken into account. Furthermore the role of transportation related and socio-economic variables are also investigated in such mode change. This study uses the stated preferences of 288 individuals who regularly use their private cars to access their job locations in the Tehran odd-even zone to calibrate six models of non-car mode consideration. Analysis of the average contributions of transportation demand management (TDM) policies to the consideration of non-car modes shows that although their contributions are about 14% for transit accessed by walking and 7% for taxi, they have never contributed more than two percent to other modes.

One of the most important factors in seismic design of structures is ductility and energy dissipation that appear with taking the structure to inelastic region. By applying the response modification factor, the seismic forces are reduced in elastic design procedure. This reduction is due to the formation of plastic hinges and energy dissipation of the structure in inelastic range. A problems in bridge design is the uncertainty in codes for defining the role of isolators in terms of R value; for example, the code No.463 has not specified the effect of isolators in R value. Besides, AASHTO guide specification for seismic isolation design, expresses that R-factor for all substructureal elements should be half of those expressed in codes for usual cases but not less than 1.50. Small value for R is due to remaining the structure in elastic range.In this study, for investigation of the R-factor, five models with an isolator connection between substructure and superstructure are developed. LRB isolators are designed according to “AASHTO guide specification for seismic isolation design”.Research results indicate that R-factors are estimated about half of the corresponding values for ordinary cases, while justifying AASHTO guide specification, it shows that the substructure of isolated bridges usually remains in elastic region.

Meta-analysis is a statistical systematic literature review which is common approach to summarize and obtain overall estimation of different studies. It has been increasingly used for evaluating the effects of various afety measures. Publication bias is an important error in meta-analysis, being cause of not publishing studies that have generally small size and non-significant impact. Funnel plot is a visual qualitative tool for detecting publication bias in meta-analysis. This paper introduces and explains two statistical tests, rank correlation method and linear regression method, based on funnel plot for detecting statistically significant publication bias in meta-analysis. These two statistical tests can be used as a quantitative tool for detecting publication bias. This is the first time that a quantitative method has been used for publication bias detections in safety metaanalysis. As a case study, the safety effects of urban traffic calming measures have been analyzed using meta-analysis. Safety effects of urban traffic calming have been gathered from 46 related studies and an overall effect for this safety treatment has been obtained. Two aforementioned tests are used to test publication bias. Meta-analysis shows that urban traffic calming measures approximately reduce the number of injury accidents, property damage accidents and total accidents by about 15, 17 and 14 percent, respectively. Statistical tests show that there is no evidence of publication bias in urban traffic calming studies

The experimental results show that using Carbon Fiber Reinforcement Polymer (CFRP) is an effective mean for strengthening RC beams. This study focuses mainly on the flexural performance of reinforced concrete bridge beams strengthened with two different (CFRP) systems: Externally Bonded Strips (EB) and Near Surface Method Strips (NSM), and evaluate the efficiency of this tow techniques in increasing the load carrying capacity of concrete beams subjected to bending due to monotonic loads. At first, the results from the FE models are compared with the ACI440 provisions and the experimental data for three beams with different conditions from researches that are in good agreement. Furthermore, the FE models were extended to simulate the behavior of full-scale bridge girders recovered from a 42-year old Interstate bridge and examined by Aidoo et al. The specimens had been retrofitted with EB and NSM techniques and subjected to monotonic loading to failure. The load deflection plots obtained from numerical study show good agreement with the experimental plots reported by Aidoo, et al. After that, the models were used to examine the influence of arrangement, number, amount of CFRP in EB technique and number of grooves, dimension of grooves, in NSM technique, on the strength and ductility of FRP strengthened beam. The effect of retrofitting on unloaded and preloaded beams was studied too. The results indicate that, increasing the percentage of CFRP increases the ultimate strength by 30%. But by changing the number of layers from 4 to 1 at the center toward the supports, the ultimate load increases 33.3% in comparison with reference beam, and the beams strengthened with NSM achieved higher ultimate load (10 per cent) than beams strengthened with EB. The level of preload, prior to the installation of CFRP, does not affect the overall behavior of the strengthened specimens.

NonPAS program has been developed for linear and nonlinear analysis of flexible pavements. Developed program allows nonlinear analysis of flexible pavements using the five nonlinear models, including K-q, Uzan, Uzan-Witczak, NCHRP 1-37A and Bilinear model. Nonlinear Analysis of flexible pavements using these constitutive models provides a more accurate modeling of both fine and coarse granular material behavior. Developed program can analyze a pavement system, including a maximum of 10 layers, which is subjected to a maximum of six circular loads. Developed program allows for calculating the responses at 300 different points in different pavement layers. In order to validate the results of linear and nonlinear analysis, computed responses by NonPAS have been compared with responses obtained from KENLAYER program. Results showed very good agreement between responses, computed with both linear and nonlinear analysis and approved that developed program can be used with high reliability for pavement analysis and design. The study also indicated the NonPAS program is able to calculate near surface responses with higher accuracy than KENLAYER program.

The transportation planning process for urban areas is typically based on partition of the area into traffic zones. In transportation planning and network analysis, it is customary to use centroid nodes to represent traffic analysis zones (TAZ). In order to load trips of each zone on the oadway network, each centroid is connected to the roadway network by at least one connector. Globally there are few studies examining the impact of connectors on traffic assignment, but all of them emphasize the importance of this subject. In this paper, we investigate the effect of selecting connector nodes on traffic assignment results and a new method is proposed to select connector nodes. To implement the concepts presented in a real sample, Mashhad has been selected for the case study. The proposed method in this study emphasizes the proximity of connector node to centroid and other criteria. This proposed method is compared with two methods from the literature. In the first method the only criterion is that the connector node must be close to the centroid. The second method introduces a measure of weight for all nodes and then selects connector nodes. To evaluate the three methods, results of traffic assignment are compared with observations of traffic volume on 87 selected links. Evaluation of results shows an improvement in the goodness of fit index of the proposed method of 3.78 and 22.2 percent compared to the first and second methods, indicating more precision in replicating real world observations.

Switches in railway tracks have discrete and complicated structures. Therefore these points are one of the most dangerous parts of a railway track. As an operational and maintenance approach it is important to evaluate and predict derailment probability in these points. As a train-track interaction problem, this phenomenon is influenced by switch geometry, switch structure and dynamic characteristic of railroad vehicle like velocity and axle load. Therefore it is important to run analyses that contain these factors and be able to evaluate the vehicle derailment phenomena. In this research, evaluation of the effective parameters on derailment of a wagon is presented considering the results of vast sensitivity analyses. For this goal, dynamical modeling of the chosen both freight and passenger wagons in a switch track using ADAMS/RAIL is developed and the effects of the switch geometry, switch structure and operational parameters of the vehicles are studied in derailment. The results showed that track gauge as well as speed had the most impacts on derailment while the even track stiffness changed the results less than 4 percent.

An attempt to increase the efficiency of transport system is a big step towards its activities to become more economical. In fact the effect of reducing the distance travelled by different modes of transportation on different economic aspects (financial costs, energy consumption, time …) is quite clear. The endeavor of man to find better, faster and more efficient ways in solving problems of personal life is endless. For a long time duplicating from the nature and discovering the nature based methods has been one of the essential branches of various human sciences.The aim of this paper is to find optimum route for freight transport of goods between the centers of 10 provinces in Iran. Here “optimization” is defined as: search for a single point or a few points in order to enhance the efficiency”. One of the most known techniques in solving optimum points is called genetic algorithm which is based on Darwin’s evolving theory. Of course this theory alone cannot fully explain and provide reasonable conclusions. Therefore, in this paper we use the John Holland’s Schema theory in order to better understanding realizing the outcomes derived from the generic algorithm.Results of this research show that it is possible to increase the efficiency of the country’s economic system including its transportation network and fleet by using TSP.