فصلنامه مهندسی حمل و نقل
سال چهارم شماره 3 (پیاپی 15، بهار 1392)

Due to the growth of urbanization, public transportation has been seriously considered in many mega cities in recent years and therefore utilization of all modes of public transportation by prioritizing them is one of the most significant issues in such cities. The purpose of this paper is to provide a method for prioritizing the public transportation in City of Tehran by applying an Analytic Hierarchy Process (AHP). In this research, at the first step, the effective criteria in priority of public transportation were defined, then by applying an expert choice technique and completing. questioners by experts in Transportation and Traffic Department of Tehran Municipality, the criteria were `revised and finalized. To complete the research, a Group Hierarchal Analysis Method was used to prioritize the existing public transportation modes in City of Tehran. The results were then compared to budget allocated to each mode of public transportation in Tehran in the past ten years, and recommendations were suggested to correct the Budget Allocation System. Results show that the subway has the highest priority, followed by BRT, bus, van taxi and taxi. Also the sensitivity analysis showed that the ranking results have the highest sensitivity to the “aim of travel” and can highly be affected by this criterion. Based on results of this research, subway, as a mode of transportation has the highest priority in the City of Tehran and therefore the allocation of public budget should be revised according to this priority.

Hazmat (i.e., hazardous material) transportation makes concerns about harm to human and environmental safety, therefore risk is considered as a main issue in all stage of hazmat shipment. In this paper, a bi-criteria algorithm is developed to consider risk and cost for the hazmat shipment. The main objective is to find the best path for carrying hazardous material form origin nodes of suppliers to destination nodes of fuel stations. Risk is identified by three groups of road accidents, population and environment. Due to a lack of exact data on three components of defined risk, linguistic variables are identified to achieve road safety experts’ view of points by questionnaires. In this case, triangular fuzzy numbers are used to convert linguistic variables to crisp values. The road network of Mazandaran province is nominated as a case study consisting of 62 nodes and 81 edges. The validation process is carried out regarding to different amounts of risk and cost priorities and the associated results are discussed. It is concluded that the decision makers are able to consider their concerns on the fuel routing problem using different priorities of risk and cost simultaneously.

Alligator cracking or fatigue cracking is the most important failure of pavements, especially in porous pavements. In this regard, the proposed models that predict the fatigue life of porous pavement can help to enhance the quality of repair and maintenance of roads, especially through the proper schedule. In this research a statistical model based on the results of experimental specimens was generated. Sample beams were made of porous asphalt with about 18% air voids. After specimen preparation, the samples were tested by four-point fatigue test machine and bending stiffness versus the number of loading cycle curve was obtained. Due to the strain controlled test, reaching to 50% of initial stiffness as failure criterion is considered. By paying attention to the experiments and logarithmic regression of results, a model to predict fatigue life of porous asphalt made of SBS polymer modified bitumen based on empirical phenomenological approach was presented. Good correlation coefficient resulted from statistical analysis indicates the proper accuracy of model.

Short-term prediction of traffic parameters such as traffic flow, speed and occupancy, have an important role in research fields of modern intelligent transportation systems. In this paper, first of all, traffic flow predictability was studied, based on chaos theory, and chaotic properties of traffic volume time-series were evaluated on the basis of Lyapunov exponent. In the prediction module, since the major problem is corrupted and noisy data due to various reasons, effect of corrupted data was reduced by preprocessing techniques. In the next step, suitable classifications were considered, based on the effects of social factors on the traffic volume. In order to predict traffic flow, according to adaptability features, self learning algorithms of neural networks and also comprehensibility of fuzzy rules which are all combined in ANFIS structure were used. The model proposed in this paper is applied to predict the real traffic flow in Ferdowsi Boulevard, Mashhad city, Iran. Comparing the predicted traffic flow value with the flow measured in reality, the results show that the proposed model can predict traffic flow satisfactorily.

The purpose of this study is to practically implement an environmental auditing program for some selected roads in Iran. To fulfill this objective, reports of implementations were scanned. Thereafter, field observations and classification of the roads were carried out. Finally, after the verification of the obtained checklists, the functionality and applicability of the audit were evaluated. To achieve this, four roads were selected and various parameters were evaluated according to the corresponding traffic load in two separate time periods. Based on examinations, the values of most of the investigated parameters were below the standard limits. Although there are no rational and meaningful relations between traffic loads and obtained values, more attention should be paid to the sources of some basic pollutants such as vanadium in soil samples. In general, the concepts of the prepared auditing framework have been approved. However, revision is required at some aspects among which the most important one is the limiting criterion of detailed auditing. The opinions of the provincial stakeholders can also be considered for determination the type of auditing. For the biological section auditing, due to the lack of corresponding statistical and informational basis, as well as the lack of criteria for comparison, certain assessment is not feasible. While regarding the auditing of water and soil pollutants sources, it can be mentioned that the pre-determined band width was more than the required limit. Thus, according to the field activities and measurements results, a bandwidth of 300m for highways and freeways and 150m for main roads is suggested. Generally, auditing is necessary for all roads within the country. However, the localization of the audits for various roads must be considered.

Degradation of transportation networks accounts for a considerable amount of damages incurred as a result of disasters. Capacity, as one of the fundamental characteristics of roadways, may be diminished in the aftermath of disasters. Hence, this paper aims to evaluate and estimate road capacity reduction with regard to different intensities of damages to the freeways and highways after disasters. Approaching the issue by simulating post-disaster conditions, it is assumed that road disruption can be modeled as a bottleneck resulting in capacity reduction. Due to the probabilistic essence of disasters and uncertainty of their temporal and spatial dimensions, one rational way to simulate post-disaster conditions is scenario planning. In this research, considering the closure of part of road width as a bottleneck, the flow through bottleneck is calculated by taking average of flows resulted from five simulation tests. Post-disaster capacity is considered as a function of base capacity and roadway/shoulder characteristics. The coefficient of remained capacity is then calculated as the ratio of the bottleneck through flow to the base capacity. Results indicate that capacity reductions are as capacity drops and is concluded that the more the number of lanes, the less the capacity drops. Moreover, the less the number of lanes, the faster and more severe the drops occurs.

In transportation economy, for estimating the benefits of travel time reduction, calculation of value of time (VOT)is required. VOT can be defined as the substitution of the marginal rate of travel time for money in driver utility function. In traditional value of time models, the main focus was on user wage rate and other parameters related to time and people travel attitudes and their trip chain characteristics were neglected. In the present proposed model, an analytical approach was applied, which unlike traditional models, does not consider the constant marginal utility assumption of parameters. In this model, a maximization approach of user utility was applied and considering time and cost constraints, a programming model was solved. Using Lagrangian multipliers, the first order condition was defined and utility function was formulated. Simone and Blume theory was applied for expanding Taylor series around their mean point. Finally by derivation due to travel time and cost of trip plan, the value of time was defined. For data gathering, the stated preference method was applied. Multiple scenarios based on previous pilot surveys were chosen and 4 types of questionnaires were used for data collection. For calibrating value of time model, a binary logit model was estimated showing the reaction of users travel choice, versus different pricing scenarios. Finally, the value of time was estimated as 43760 rials (in the year 1390) and the sensitivity analysis showed that when this cost is assigned as the entrance toll for even-odd restricted area, about 40 percent of users would choose their private cars.

In the absence of historical accident records, road authorities are faced to a problem of safety investment. Specially, this issue is arisen in case of improving the safety level of a road or a road network. Although, some studies have pointed out the hazard index of some road elements aggregately, no research is disaggregately addressed the issue. This paper addresses a disaggregate approach to identify the risk level of 47 elements of two-way two-lane roads. By introducing analytical hierarchy process (AHP), this paper explores the contribution of each road element to the road safety state. Results gained by the studied road safety experts showed that the main accident risk in the roads is due to parking and other roadside land uses, bridges, accesses and intersections, tunnels, curves and segments respectively. The study also shows that in the range of investigated factors, the top twelve factors are responsible for about 50 percent of accidentprobability.