فصلنامه مهندسی حمل و نقل
سال هفتم شماره 2 (پیاپی 26، زمستان 1394)

Understanding the underlying structure of vehicle crashes is essential for improving safety on the roads. Past research has found that accident tend to cluster both spatially and temporally. This paper applied spatial, temporal and spatio-temporal techniques to investigate patterns of Road Accident in Karaj-Qazvin highway-Iran between 2009 and 2012, at different characters. Spider graphs were adapted to identify temporal patterns of vehicle crashes at different situation. The spatial structures of vehicle crashes were analyzed using Fuzzy Kernel Density and then result was compared with Kernel Density Estimation. Comap was then used to demonstrate the spatio-temporal interaction effect on vehicle crashes and spatial pattern of accident at different characters. Characters that influence at spatial and temporal pattern of accident are: Time, Week day, Type of accident (Fatal, Injury and Non-Injury), Type of Collision (Vehicle with Vehicle, Vehicle with Pedestrian, Vehicle with Objects and Overturn), weather situation (Clean, Rain and Snow), Human Behavior (Hurry, Fatigue and Sleepy and Low Inattention). The results show significant differences in spatiotemporal patterns of Road Accident for various crash causes. The techniques used here have the potential to help decision makers in developing effective road safety strategies.

Vertical stiffness of ballast railway is an effective parameter on track quality level and maintenance cost. As track dynamic surcharges could have great impact on the majority of stiffness, this parameter need to categorize as static or dynamic. Plate load test (PLT) and light weight deflectometer test (LWD) are two widespread used tests in railway construction processes to measure static and dynamic stiffness’s respectively. PLT is a time consuming test and its implementation is usually accompanied with temporary block of track but LWD have the opportunity to perform faster. On the other hand, static stiffness measured from PLT is the parameter which railway standards and guidelines used to define their criteria about the quality of different track pavement layers. So this paper is concerned to extract a mathematical relation between the results of these two tests. Linear regression method used for this purpose. Static and dynamic stiffness ratios are derived for both situations, before and after tamping process. Finally a finite element numerical model used to calculate vertical stiffness of ballast layer.

When bridges are subjected to large inelastic deformations during near field ground motions, they do not often return to their initial vertical positions and may have considerable residual displacement. Even if collapse is not occurred, large residual displacements may make them unusable or irreparable. This large residual displacement causes no collapse in bridges while it may make them unusable or irreparable after earthquake. Therefore, the measurement and estimation of residual displacement are of a great deal of importance in assessment and serviceability of bridges after earthquake.The Initial hysteresis models have been developed for dynamic analysis of conventional concrete columns and are often unable to estimate high residual displacements occurred in biased and one-sided motions. The aim of this research is development a new hysteresis model based on peak displacement oriented which is able to provide adequate residual displacement compared to conventional models. This multi linear peak oriented model considers strength deterioration in half cycles in addition to stiffness degradations in unloading cycles. Yielding points differ in both positive and negative sides of hysteresis model enabling us to define a different elastic stiffness of both sides in asymmetric concrete sections.
Another remarkable property of this model is breaking points and strength deterioration in unloading and reloading stages, respectively.The performance of conventional hysteresis model was investigated in estimation of seismic residual displacement in cyclic and dynamic analysis in addition to a new combinational hysteresis model. The obtained results indicate that the new studied hysteretic model has higher accuracy in comparison with other current models.

Considering the high rate of road accidents, this study sought to assess the impact of road surface markings as an approach to traffic calming. For this purpose, the experiment was planned and conducted in a driving simulator. 40 participants took part in this experiment; however, the data obtained from one of them was removed due to a malfunction of the simulator. The remaining 39 participants, (32 males 7 female) with a mean age of 28 years and a minimum of 3 years of driving experience travelled over 5,000 km were investigated. Participants were subjected to one base scenario without any signs, and four scenarios including continuous transverse bars, peripheral transverse bars, dragon’s teeth marking, and marginal hatched marking. In each scenario, data regarding speed and vehicle lateral position were collected and analyzed. The speed and lateral position profiles were drawn for each scenario. Results showed that the average driving speed reduced in a range from 12 to 15 km/h in three of the scenarios with interventions. However, in the scenario with marginal hatched marking, reduction amount was equal to 21/9 km/hr. The lateral displacement of the drivers increased in the first scenario and not much reduced in the second and third. On the other hand, a reduction equal to 17/3 cm was spotted in lateral displacement of vehicles in the fourth scenario in which marginal hatched marking was implemented.

The aim of this paper is ride quality analysis of rail vehicles in the straight line rely on EN and UIC methods. To achieving this goal, a 9 degree-of-freedom (DOF) ride dynamic model of wagon has been described. The ride dynamic model of ERRI benchmark vehicle simulated in SIMULINK toolbox that its inputs were class 3 and 6 of USA railway. Wagon’s dynamic response versus different longitudinal acceleration has been obtained. The ride comfort index calculated in MATLAB software. The results show that the ride comfort index increases as a function of starting longitudinal acceleration, especially in standing passenger. The point B ride comfort index (corner of wagon) is greater than point A (midpoint of wagon). This difference is very sensible in low quality track, because roll and pitch acceleration of car-body in point B are much greater than point A. At same acceleration, ride comfort index value in standard method was lower than full method for standing passenger. Full method should be using for evaluation of ride comfort in metro wagon standing passengers.

In this study, planning of activity-based personal trips in the public transportation networks that is of importance for tourist is developed. Public transportation networks are organized by time-dependent models. In this model the edge-weight is not constant and time-dependency of departure. Since trip planning has combinational nature and is optimization, therefor it is modeled with genetic algorithm. This algorithm is among the ways which use meta-heuristic search in order to find optimum solution. In this study structure is proposed that receives the raw data of day and time of the trip, the favorite cities of the traveler with their priority rating, the duration of activity in a particular city and its timing along with selected transportation networks from the traveler and designs trip planning in a way that in the allocated time the traveler gets the highest benefit rate of their visit and activity in the chosen cities. Among the purposes of this study are: modeling of personal activities, tip planning with the aims of optimize the time of trip and evaluating the proposed structure. In order to evaluate the proposed framework a series of data from timetables of transportation network of 15 Iran province centers for three transport networks: airplane, bus and train for travelling in the selected cities were collected and frameworks along with modeling were evaluated. So for its evaluation 50 trips with different starting time and tour duration were performed that in average have relative error 5.2%.

Waste collection is a highly visible municipal service that involves large expenditures and difficult operational problems, plus it is expensive to operate in terms of investment costs (i.e. vehicles fleet), operational costs (i.e. fuel, maintenances) and making small improvements in this area can lead to huge savings in municipal expenditures. Among the issues raised in this context, changes in the pattern of waste collection in order to explore different, and consequently considering the uncertainty of the data. Study of urban waste collection problem in terms of uncertainty can help managers and decision-makers to make appropriate decisions.
In this paper, The Capacitated Arc Routing Problem under fuzzy demands is described. Due to uncertain nature of demands (waste amount) and the difficulty of determining the real amount, a fuzzy chance constrained programming is designed to model the problem, based on the fuzzy credibility theory. A hybrid genetic algorithm incorporated with a heuristic algorithm, a simulated annealing, a genetic algorithm and a stochastic simulation is developed and proposed to solve the model. The experimental results have shown that the proposed algorithm has appropriate performance in comparison with CPLEX. At the end of paper, a case study in urban waste collection of Isfahan is implemented to determine the optimal policy in uncertain circumstances.

Highway construction industry produces millions of tons of recycled asphalt annually, large amounts of which usually remain unusable and occupy the stockpile areas. Therefore, the suitable use of these materials is inevitable. Although, using of recycled asphalt pavements (RAP) in asphalt mixtures is common, there are few consideration about using of these materials in Portland cement concrete especially roller compacted concrete. In this study, RAP materials were used as coarse aggregates, fine aggregates, and both fine and coarse aggregates in the Roller compact concrete mixes. The energy absorbency of specimens were analyzed with the force-deformation curves that obtained from the three-point flexural test. Results revealed the beneficial effects of the RAP material on the energy absorbency or material flexibility. Based on the laboratory results, replacing the coarse part with RAP will achieve an intermediate mixture which exhibited higher flexibility than the reference specimen and higher strength than two other mixes which containing fine RAP and both parts of RAP.

Due to the important role in providing safe conditions for train movements, railway interlocking systems are considered as safety critical systems, hence it requires advanced formal modeling techniques and step-by-step development to ensure safety, quality and reliability of the system. State flow toolbox of MATLAB software is a convenient tool for formal design. In this paper, a new simulator of railway signaling and interlocking systems based on discrete-event dynamic is presented. with receiving the basic information about physical features and policies of railway network, this simulator models and simulates the interlocking system. The primary features of this simulator are facility in design and developing the interlocking system and its ability to test the new interlocking functions in it. The main innovation in this simulator is that the elements of the railway network are designed based on discrete-event dynamic and its ability to develop and communicate interlocking system with other railway traffic control systems. To evaluate the performance of the proposed simulator, we simulate the interlocking system of a railway station and line 2 of Tehran metro in this simulator.

In most developed countries, reduction of walking to school among children has become a considerable problem causing traffic congestion, air pollution especially near schools, lack of independent decision making abilities and lack of skills in social networking in children and also it increases rate of obesity. So far, engineering efforts such as development of walking facilities on streets leading to schools has not necessarily led to promoting school children walking. Hence, this paper has focused on parental attitudes towards traffic, safety besides socio-economic factors, in choosing school trip modes. Particular attention is paid to elementary students walking mode in the frame of questionnaire survey with their parents. The research questionnaire was particularly designed for this purpose and distributed among 290 families with students of elementary grades one to three in four elementary schools (including both public and private and both boys and girls schools) in district one of education in May 2013 in Rasht. Based on the data from this field questioning, Multinomial LOGIT Model and MANOVA were used to survey effectiveness and relationships of attitudes components towards traffic safety and socio-economic factors in choosing school trip modes especially walking. Results show that parental believing in safety problems and parental trust towards traffic safety experts, its rules, regulations and priorities besides some socio-economic factors in choosing walking, school service and household vehicle mode are significant. Results also show that children dropped to school by motorized modes have parents believing more towards safety problems and greater confidence towards experts than others who allow their children walk to school. Results indicate a lack of perceived safety of walking mode in school trips and parents trust towards traffic experts claim of lack of walking safety. Also, parents who perceive more traffic safety rules and priorities, use household vehicles for taking children to school less. It seems necessary for authorities to persuade parents into choosing walking for their children using some strategy such as SR2S (Safe Route to School) and gaining the trust of parents to choose walking.

In recent years, congestion pricing is applied as one of the main demand management methods in urban areas. Although, numerous studies had been performed in urban road networks, but only few of them is about link pricing in urban areas. Sadr elevated highway, recently built in Tehran, is the case study of this paper. This route which has many alternative routes (for example Sadr highway in level 0 elevation) has the potential for link pricing in Tehran. Due to this fact that currently there is no any pricing mechanism in this route, a stated preference method had been applied for defining the reaction of users to route pricing. Over 1100 samples were gathered and coded in a database. A binary logit model was applied for modeling the route choice behavior of users due to pricing. Results showed that using the route in peak hour cause to increase the willingness to pay. Users with mandatory trip goals, have more will to use faster routes. Also, results showed that users with more expensive cars and higher education level pay more for priced routes. Sensitivity analysis showed that if the pricing toll is going to be set on 2000 tomans, about 42 % of demand have the willingness to pay. With raising the cost, the willingness to pay tends to reduce significantly. For example, if the toll is set to 5000 tomans, 67 percents of total demand would tend to other alternatives.

Evaluation of railway transportation efficiency is one of the most important issues of railway transportation industry. National Iranian Railway includes 15 operational regions which operate under supervision of Iranian Railway headquarters. In this paper, we have applied Data Envelopment Analysis (DEA) to measure the efficiency of these 15 railway regions (DMUs) both in Variable and Constant Returns to Scale. To achieve this goal we have applied two models with different outputs. The second model contains railway accidents and fatal data. We have also ranked the efficient railway regions by applying a heuristic ranking technique to find out the most efficient one. Consideration of desired and undesired outputs is a new approach in efficiency evaluation of railway regions that has more reliable results. The results reflect the necessity of considering the undesired outputs for a more realistic overall efficiency evaluation and accordingly, appropriate corrective recommendations are presented for improving the performance of inefficient railway regions.