Journal of Transportation Engineering
Year:2012 | Volume:3 | Issue:2 (10)|Papers Count:6

Seismic stability of infrastructures against earthquakes is one of the most important engineering challenges in railway transportation systems. Present literature shows that there are many considerable technical shortages in this issue. Therefore a 3D FE model including the beam elements for modeling the rails and sleepers as track superstructures components, a series of lumped masses with spring and dashpot for modeling the ballast, sub ballast and subgrade as track substructure components and a number of stiffness and damping for considering of longitudinal and lateral resistance was developed. For validation of the model, comparing the results of a shaking table test with seismic analysis outputs of the model is compared. Accordingly this numerical model can be employed for seismic railway track analysis. The influence of earthquake on seismic behavior of railway track by imposing the artificial accelerograms with variation of peak ground accelerations (PGA) from 200gal to 1000gal was studied. For above mentioned assessments, the operational conditions including longitudinal and lateral deflections of track, as well as structural conditions consisting of axial forces, shear forces and bending moments of rail and sleeper were investigated.

The first travel demand forecasting models were created on an aggregate basis since 1950s. These models included four independent modeling steps: trip generation, trip distribution, modal split and traffic assignment. However, after observing the shortcomings of this process in analysis of strategies and incorrect results of demand forecast, development of disaggregate methods which have a behavioral basis was welcomed by planners and decision makers of transportation industry since 1970s. After testing many methods such as travel chain, activity based methods emerged in which the activity is considered as the factor causing the travel. Based on this, in most of the large cities of the world and especially in the United States of America, activity based models were created and the results were evaluated and implemented. Nowadays, many of the large cities of the country are facing problems related to management of traffic demand. In this paper, the required information was drawn from the questioning of inhabitants of Tehran performed by Tehran Comprehensive Transportation & Traffic Studies Company. By applying the activity based structure to the existing data bank, the activity based data base was prepared and by unavailable, two variable and multivariable analyses of this data bank, the factors affecting the utility functions of daily activity pattern, time and vehicle of the primary tours were identified. The three independent, nested and joint decision making structures were created and analyzed by logit models. Considering the analyses performed, the independent structure was evaluated as more suitable for the sample of the study and by using that, a general knowledge of the daily activity planning of individuals was provided.

There is discrepancy between offence and non-offence driving behaviors. This study aims to determine the effect of some of person and vehicle related factors on offenses status of road traffic injuries. A descriptive study was carried out by census method of 557182 subjects with offence and non-offence outcomes. Variables such as: age, sex, speed, license and vehicle type were studied. Findings is presented by descriptive statistic and analyzed by binary logistic regression test. Results showed: age factor had no impact on offence. Males were more offence than females (OR=1.205) in urban ways and lower offence than in sub urban ways (OR=0.499). The most effective factor was speed (OR=3.60) in sub urban ways. B1 type license in urban and suburban were (OR=2.998, OR=2.682) and motorcycle were (OR=1.762, =2.190 respectively on offence status). The chance of offence in injury occurrence by speed factor was five times more in suburban axes. Based on speed factor, gender and among motorcyclist especially in suburban axes appropriate planning and strategy by authorized organization is recommended.

Wagons experience different types of vibrations while moving on the rail, amongst which the lateral vibration is the most important one. In higher speeds, the lateral vibration causes Hunting, which is a specific inconstancy. In this article the lateral vibrations were investigated by deriving nonlinear equations of motion of a high speed passenger wagon while moving in a straight path. Sources of nonlinearities of the wagon model are wheel profile and creep forces in wheel and rail contact. The wheel profile has been imported into the equations by using a multi-nonlinear function and in order to extract the mathematical model of wagon, heuristic creep theory was used. In addition, both single and double point wheel-rail contact have been considered in the modeling of wagon.21 degrees of freedom are used for modeling of the wagon, which are lateral and vertical displacement of each wheel set, the lateral and vertical displacement, roll and yaw angle of each Bogie frame, and the lateral and vertical displacement, roll, pitch and yaw angle of the car body.The governing equations of motion were solved using MATLAB. Results show the critical speed of wagon is 83 m/s.

High occupancy vehicle (HOV) lanes increase the capacity of freeways by providing the incentive of a shorter travel time to those using buses, vanpools and carpools. These lanes are designed to move more passengers per vehicle-trip and to save travel time. HOV lanes may increase the efficiency of a road through a reduction in the number of single occupant vehicles. Considering the high expenses of constructing these lanes, it is necessary to justify their efficiency through research. In this paper, demand diversion models are proposed and calibrated based on the data gathered through a field survey designed exclusively for this purpose. The questionnaire included 13 questions regarding travelers’ characteristics and their stated preferences towards carpooling based on different time-saving scenarios. The field interview survey administered in 2012 on seven days at four gas stations with rather long queues resulted in the collection of 489 filled questionnaires. Based on the final 419 questionnaires validated, logit models were estimated using travel time reduction for educational and work trip purposes.Results show that time reduction is not the only effective factor in carpooling selection, but other factors like cost reduction and convenience can also be effective. Three scenarios providing a range of potential impacts of HOV lanes on diversion of single occupant vehicle trips is considered. In the specific hypothetical scenario considered in this paper, the range of diversion to HOVs was found to lie between 14 and 44 percent, which may show a significant impact on the performance of the urban transportation systems through system management strategies.

With the increase of railway transportation demand in the most railway networks, railway operators encountered lack of capacity. For improvement of capacity, the basic planning is required. The railway capacity is dependent on infrastructure, traffic, and operating parameters. The aim of this study is to present a methodology to investigate the appropriate solutions for increasing the capacity of railway bottlenecks. In this study, a new optimization model is presented based on multi commodity network flow model on a space-time network. The objective of the proposed model is to maximize the number of trains in the reference time. The inputs of the model are the characteristics of each train type, infrastructure attribute and network configuration. The most important constraints used in this model are related to the different kinds of the trains and number of the siding tracks at the nodes. By defining the proper criteria based on the capacity and the cost, operation of different proposed scenario for increasing the capacity is studied for that railway. We used the model to evaluate the solutions for increasing the capacity of Badrood-Ardakan railway as one of the Iranian rail bottlenecks. The results show that based on percentage of capacity index, the construction of two new nodes and two siding track between the two existing stations is the best option. Based on the cost of adding a train, the construction of two new nodes with a siding track between the two existing stations is the best choice. Finally, based on the cost–capacity index, building a new node (with a siding track) between the two existing stations is the best option.