نشریه فناوری حمل و نقل
پیاپی 28 (بهار و تابستان 1396)

Increasing population and vehicles, causes traffic congestion and impaired in vehicles movement. Traffic signals coordination in a road network has an important influence on total delay reduction, avoiding congestion and queued rejection in urban networks. In this paper in order to improve the performance of an under saturated network and minimization of the total delay, a model is presented. In this model the total delay in the network is minimized by adjusting the traffic signal timings in the network including cycle lengths, green times and the offsets. This model is formulated as a mixed integer linear programming (MILP), so it can be solved by linear methods.
In order to validate the presented model, the signal timings results are compared with the signal timings results of synchro software by simulating in Aimsun and Simtraffic softwares. The results of this study, reflect the positive performance of the presented model for under saturated conditions.

Horizontal curves are one of the critical regions in suburban highways in which many of the skidding and running off road accidents happen. A well designed shoulder can reduce the peril of crashes. Main purpose of this study is to find influences of shoulder type and vehicle dynamic parameters on skidding in horizontal curves with considering factors like: side friction factor (friction between the tires and road surface), driver’s behavior and road geometry by the means of vehicle dynamic simulation. Different conditions for an unwanted vehicle running off are supposed in this study. Current research includes: 1- three dimensional vehicle dynamic simulation by Carsim and Trucksim, 2- Analysis of the speed vs side friction factor curves for three types of vehicle (Sedan, SUV and Truck), 3- Introduction of a nonlinear multiple regression model for the relationship between variables via SPSS statistical software. Results show that widening the shoulder leads to an increase in the side friction factor which prevents the vehicle from skidding and moving towards the foreslope.

Injury severity is an important index to analyse cost of crashes. Several approaches have been used to model and predict the crash severity. In this study, using road traffic accidents in seven provinces of Iran (Isfahan, Khuzestan, southern Khorasan, Qom, Qazvin, Kerman and Mazandaran), and Binaary Logit model has been used to predict the fatal or injury crashes. The effect of important variables on the crash severity of each of the three types of accidents involving motorcycles, sedans and trucks was investigated. Also, factors such as increasing the difference in weight of vehicles, deviations to the left, increasing the age of drivers, pedestrian presence and exceeding speed limits lead to increased crash severity and fatal accidents.

In this research, through carrying out experimental tests and finite element simulation, the crushing method of empty and foam-filled thin-walled structures under the influence of axial, Quasi-static loading has been compared. In experimental study, the conical samples are made through spinning method. These samples are compressed between two rigid plates under quasi-static loading conditions, and then the collapse mechanism, the crushing force fluctuations and absorbed energy are calculated. Simulation of tested specimens has been executed by ABAQUS software in 3- dimensional models and through explicit method. The comparison of numerical and experimental results showed that the present model provides an appropriate procedure to determine the collapse mechanism and load-compression curve. The validated finite element model was then used for the parametric studies, in order to determine the effect of the empty and filler tube geometry parameters (i.e. semi-apical angle, foam density, wall thickness) and loading parameters (i.e. impact mass and impact velocity) on the energy absorption and factor crushing load ) .(

One of the main problems in densely populated cities is road traffic accidents and traffic jams at the high-speed signalized intersection. In this case, due to the amber light zone, drivers are confused and skeptical for crossing or stopping at stop line of the intersection. Failure to make the right decision in the Dilemma Zone causes fatal accidents at the intersection. In this paper some basic subject about signalized intersection, including the identification of dilemma zone areas, determining boundaries of dilemma zone and affecting factors on this situation, safely protection of dilemma zone and identify the drivers behavior in that area are discussed and some solutions presented. The result of the research show that in order to reduce the rate and severity of crashes and the number of vehicles involved in the dilemma zone areas, increased amber time, all red time and the green light extended system should be used, also if we could use the advanced warning system, it is better to that AWF and CFSSA models should be used before the PTSWF model. Visual stimuli and off-road advertisement are also a very important aberrant behavior of drivers in the dilemma zone areas.

Factors affecting the skid resistance are devided into three categories: weather conditions, traffic fluctuations and parameters related to vehicle. One of the factors related to the pavement is the average depth of coarse texture. The main objective of this study is to obtain an average depth of pavement texture. In order to achieve this goal, an appropriate aggregation was selected from the Iran’s road pavement Regulations (open and continuous gradation 5). Some samples were made by Marshall Test using the selected gradation and six different types of pure bitumen 60-70 with the percentage of 4, 4.5, 5, 5.5, 6, 6.5% and calcareous mountain broken materials. After analyzing the results for each sample, the optimum bitumen percentage was obtained for each sample. Regarding the optimum bitumen, gyratory samples were made. The coarse texture effect on these samples was investigated through sand spread method (based on ASTM E965-96) and the most appropriate gradation was selected regarding the skid rtesistance. The results showed that an average depth of open coarse is better than continuous course. Also porous asphalt could be an appropriate option to eliminate the phenomenon of skid resistance due to possess suitable vacuum drainage and continuous transverse surface water.

The objective of this paper is to review freight train derailment risk models in order to determine effective parametersassociated with train derailment. Accordingly, this research is basis-pure study andliterature review of the relevant studies for the period of 1991 to 2016. The studies are dividedinto two groups.(1) Analysisof railway derailment causes (2) risk analysis of derailment that is function of frequency and severity.So, identify relations, contradictions,gaps and inconsistencies in the literature thenrelevant improvement approaches are presented.Results of this research represent the causes of major freight train derailment and different train derailment risk models.Finally, five major causes and four risk modelsdetermine for freight train derailments and find out there area limited group ofparametersliketrain speed, derailment causes and trainlengthconsideredin train derailment risk modelswhile it can be expand to consider more parametersas number of loaded wagons, weather condition and etc.