جستجوی مقالات مرتبط با کلیدواژه « تخصیص ترافیک » در نشریات گروه « فنی و مهندسی »

The Traffic assignment problem in the transport networks is formulated as a convex optimization problem using simplifier assumptions. Link based, path based and bush based algorithms have been presented to solve this problem, among which the link based algorithm have found more applications thanks to their low memory requirements. The link based algorithm of Frank-Wolf (FW) is yet amongst the most popular assignment algorithms, because of its simplicity as well as high convergence speed during the initial iterations. However, the low convergence rate of this algorithm near the optimal solution has driven many studies that focus on modifying the FW search direction, resulted in newer link based algorithms. Among them are conjugate direction algorithms which are more effective and simply implementable. These algorithms include PARTAN, conjugate FW (CFW) and bi-conjugate FW (BFW). This paper uses the Chicago Regional and Sioux-Falls test networks to make direct comparisons among these algorithms with respect to the CPU time and iteration number needed to reach various accurate solutions. The results for Chicago show that, compared with the FW algorithm, the three algorithms CFW, PARTAN increase the convergence speed to the relative error of 10-5 (i.e. a stable solution) by about 89, 72 and 63%, respectively, while only the BFW can reach to a 10-6 relative error. Comparing the results from Sioux-Fall with those of Chicago demonstrate that the performance of the conjugate directions Algorithms improves as network size decreases.

The interaction between urban land uses and urban transportation system is one of the most important issues in traffic policy and urban management. In order to investigate how these land uses interact with the transportation system, the construction effects of “Tehran Mall” trans-regional complex on the general measures of Tehran transportation system and its District 22 are studied based on the 4-step modelling approach. In order to modeling the travel attraction of this complex, models of mixed trans-regional land uses are calibrated using volume counting and query information. Then, two scenarios are defined for Tehran in the year 1400. The first scenario is the status of the Tehran transportation system in absence of Tehran Mall and the second one its status in presence of Tehran Mall. After modeling both scenarios in EMME software, a comparison between the two scenarios is performed based on the general measure of the transportation system, which include transportation network measures, auto and public travel demand, air pollution emissions and fuel consumption. Comparing the results of these two scenarios shows that in the case that Tehran Mall is constructed, important measures of Tehran transportation system improve. It can be concluded, therefore, that the construction of a trans-regional attractive land use in an area with unsaturated traffic capacity can attract part of the travel demand from other areas, and so can improve the transportation system while reducing emissions.

Correction old OD matrix is one of the Cheapest methods for provide the Origin-destination matrix for the base year, which are based on the observed values in selected links. In each of these methods, in order to obtain the share of each links from the demand between the ODs, the primary matrix (and in subsequent replicates, the modified matrix) is assigned to the network. By introduction of fuzzy concept, new methods for correcting the OD matrix have been refined, which called the fuzzy flow method (TFF). This method uses the matrix assignment as well as other methods in the matrix correction process. Considering the importance of the assignment method used in matrix correction, this paper deals with the effect of traffic assignment method in traffic fuzzy flow correction method. The results show that the use of the user equilibrium method is superior to the stochastic and incremental assignment, and the good fit coefficient in the user equilibrium method is equal to 0.82, while in the stochastic method, this R2 is 0.72 and in the incremental assignment has a value of 0. 67.

Planning and construction of charging station are important aspect of promoting the development of electric vehicle. Considering the interactions between power and transportation industries, charging station planning require a systematic consideration of relevant issues including: traffic network characterizes, charging demand and electric network constraint. The scope of this study is optimal sitting and sizing of fast charging stations in distribution network considering uncertainties. Firstly, a stochastic model based on queueing theory and user equilibrium based traffic assignment model is developed for electric vehicle charging demand. Then, annual cost of investment and energy losses is minimized under chance constrained framework. The probabilistic aspect of problem are solved using point estimation method and Gram-Charlier expansion. In Addition, to consider uncertainties in final decision making, probabilistic dominance models are introduced. Finally, planning result of coupled distribution and traffic systems are presented to illustrate the performance of the proposed approach.

Transportation planning studies are generally based on dividing the study area into a set of traffic analysis zones (TAZ) based on a set of rules. Each zone is then represented by a node named centroid, which is assumed to be the origin and also the destination of all trips of that zone. Considering the sensitive and focal role of the location of centroids on traffic assignment results due to this rather big assumption which may cause large errors in results, very little research is found in the literature. Due to this research gap in this field, the current paper tries to analyze and examine the impact of centroid location on traffic assignment results. The traffic assignment applied is that of Wardrope’s user equilibrium (UE) principle implemented in VISUM transportation planning software package and the quantitative measures are those of hourly flows on different links of thetransportation network. Predicted link flows for different scenarios are compared to the observedflows on the same selected links. To discuss and analyze the implementation challenges, the real sized network of the second largest city of Iran, namely the city of Mashhad is selected as the case study. Three different methods for selecting centroids are presented to analyze their impacts on link flows. For each method, two different scenarios of choosing connector nodes are presented: in the first scenario, number of connector nodes is variable for different zones but their locations are fixed for each of the three methods. In the second scenario, having chosen the centroid according to each of the three methods, the closest node to the centroid is selected as the connector node. Results of this research, based on the comparison of predicted and observed flows on 87 links of Mashhad transportation network, show that for the assumptions of this case study, changing centroid location can cause a change in the coefficient of determination of the linear regression line of predicted-observed flow links of 1.7 percent in the first and 20 percent in the second scenario of selecting connector nodes. This noticeable impact in a real case with realistic assumptions can be considered an important confirmation of such research and also the need for further research in this rather unattended field.

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 roadway 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, the effect of selecting connector nodes on traffic assignment results is studied and a new method is proposed to select connector nodes. To implement the concepts presented in a real sample, City of Mashad, Iran, was selected as 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 were compared to 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.

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

One way to reduce traffic congestion is to increase network capacity. The solution is applicable by either adding new links to the network or improving the existing links. The purpose of this study is to provide a model able to determine the optimum capacity of network links considering an elastic demand. The problem is known as Continuous Network Design Problem (CNDP) in transportation. The model has been developed as a bi-level program. The objective function at the upper level is to maximize the consumer surplus for which Simulated Annealing (SA) algorithm has been used to determine the optimal solution. The lower level problem is formulated as assigning traffic considering elastic demand for which Frank–Wolf method has been used. Two networks have been used to compare the results. Also, sensitivity analysis on the parameters of SA was done to find optimum values for the parameters. Finally, after accomplishing another sensitivity analysis on the budget, consumer surplus changes have been reported against budget variations.

Numerous worldwide studies have examined the effect of zone aggregation on the results of traffic assignment worldwide, but there are very few studies in the country have investigateding this effect on the various stages of transportation planning. Existing literature reveals the important role of zoning methods on different stages of transportation planning. In this paper, a quantitative research has beenis conducted on the effect of zone aggregation, particularly, on the results of traffic assignment for the a case study of in Mashhad. In the aggregation process, emphasize has beenis placed on homogeneity of zones and respect appreciating to the boundaries and physical barriers, where possible. For comparison purposes, predicted values for the four different research scenarios are have been plotted and analyzed statistically, based on statistical parameters, such as the coefficient of determination and t- test. Results show that aggregation (reducing the number) of zones for the case under study, does not improve traffic assignment model results expressed in link volumes, as expected.

Traffic allocation issue, the issue of possible arcs in a stream distribution network Transport. To solve this problem, and the nodes in parentheses Haltykh Network has infinite capacity) for flow (be repetitive procedures Performance such as Frank Wolf exist. In these methods Khtyshdh Zyrmsylhy In each iteration, equivalent to the shortest path between pairs of origin issue Destination. But Haltkly, Kaman and capacity limited network nodes And considering explicitly these constraints causes the Zyrmsylhy Khtyshdh multi commodity flow problem with minimum cost and in turn The resulting solution is very difficult. One way to solve this problem considering Implied capacity constraints using a penalty function sensitive to capacity Is that adding this function Bhnhvy fine time to visit parentheses Compliance due to capacity constraints. Traffic assignment literature, application of results Fined functions for considering capacity constraints arc in real networks There is clear and well their performance, while such results for Considering the node capacity constraints have been reported. In this paper methods Penalty function in solving dynamic traffic assignment with capacity constraints The node capacity constraints arc of Bhmratb harder is is used for And network performance test for several different dimensions and a network Real dot.

Different driver's perception in routing is one of motivations to different driver's routing models. Drivers routing are usually based on undeterminstic general costs of available routs which the fact of uncenteainity is the background of logit models. Independence of Irrelevant alternatives is the core of logit models which is not satisfied in multinominal logit models, therefore extended logit models have been extended to overhelming this problem. Great mathematical literature review of different logit and extended logit models have been investigated in this paper with its methodlogy and usage on unic Allsop and Charlsworth proposed network. Results of these various logit models have been obtained based on proposed procedure and there are evidences that various logit models tend to have same result in low and also high(about twice of low) demands. Between these levels of demand there are different results by each of these models. Beside proposed algorithm for different logit model's applications, the chance to recognize their effect on link volumes and use of volume-based link-cost models are the distictive effort of this paper. The main innovation of the paper came out by taking into account the intersections effects on rout costs and their delays as a cost to network's performance index.