Transportation Network Optimization Research Articles

Optimal public transport networks for a general urban structure

Using a quite general parametric description of an urban setting in terms of its network, centers structure and demand pattern, we find the optimal spatial arrangement of transit lines out of four basic strategic competing options: direct, exclusive, hub-and-spoke and feeder-trunk. We identify clearly the relation between the characteristics of both the urban setting (mostly monocentric, polycentric or dispersed) and the users (transfer penalty, patronage) with the line structure that shows the best response.

Optimization of transport network in the Basin of Yangtze River with minimization of environmental emission and transport/investment costs

The capacity of the ship-lock at the Three Gorges Dam has become bottleneck of waterway transport and caused serious congestion. In this article, a continual network design model is established to solve the problem with minimizing the transport cost and environmental emission as well as infrastructure construction cost. In this bi-level model, the upper model gives the schemes of ship-lock expansion or construction of pass-dam highway. The lower model assigns the containers in the multi-mode network and calculates the transport cost, environmental emission, and construction investment. The solution algorithm to the model is proposed. In the numerical study, scenario analyses are done to evaluate the schemes and determine the optimal one in the context of different traffic demands. The result shows that expanding the ship-lock is better than constructing pass-dam highway.

Relating the 3D electrode morphology to Li-ion battery performance; a case for LiFePO4

One of the main goals in lithium ion battery electrode design is to increase the power density. This requires insight in the relation between the complex heterogeneous microstructure existing of active material, conductive additive and electrolyte providing the required electronic and Li-ion transport. FIB-SEM is used to determine the three phase 3D morphology, and Li-ion concentration profiles obtained with Neutron Depth Profiling (NDP) are compared for two cases, conventional LiFePO4 electrodes and better performing carbonate templated LiFePO4 electrodes. This provides detailed understanding of the impact of key parameters such as the tortuosity for electron and Li-ion transport though the electrodes. The created hierarchical pore network of the templated electrodes, containing micron sized pores, appears to be effective only at high rate charge where electrolyte depletion is hindering fast discharge. Surprisingly the carbonate templating method results in a better electronic conductive CB network, enhancing the activity of LiFePO4 near the electrolyte-electrode interface as directly observed with NDP, which in a large part is responsible for the improved rate performance both during charge and discharge. The results demonstrate that standard electrodes have a far from optimal charge transport network and that significantly improved electrode performance should be possible by engineering the microstructure.

A Study on International Multimodal Transport Networks from Korea to Central Asia: Focus on Secondhand Vehicles

ABSTRACT Currently, high-income countries use multimodal transportation to export large quantities of secondhand vehicles to low-income countries. Secondhand vehicle export has shown its highest growth in recent years, especially in Korea. The problem of transporting secondhand vehicles from Korea to Central Asia is becoming an important issue, but few researchers are interested in it. The objective of this research is to determine the optimal transport network for exporting secondhand vehicles from Korea to Central Asian countries by combining experts’ opinions and real data from existing transport networks. The fuzzy Delphi method was applied to obtain factors to evaluate alternative multimodal transport networks for moving secondhand vehicles from Korea to Central Asian countries by judgment from experts. The analysis shows that among the five factors (total cost, total time, reliability, security, and transportation capability), total cost is the most considerable factor, followed by reliability, transportation capability, total time, and security. Additionally, in the mainly three multimodal transport networks, the sea+Trans-China Railway route is ranked first, followed by the sea+Trans-Siberian Railway and sea+truck routes.

Biological transportation networks: Modeling and simulation

We present a model for biological network formation originally introduced by Cai and Hu [Adaptation and optimization of biological transport networks, Phys. Rev. Lett. 111 (2013) 138701]. The modeling of fluid transportation (e.g., leaf venation and angiogenesis) and ion transportation networks (e.g., neural networks) is explained in detail and basic analytical features like the gradient flow structure of the fluid transportation network model and the impact of the model parameters on the geometry and topology of network formation are analyzed. We also present a numerical finite-element based discretization scheme and discuss sample cases of network formation simulations.

A Flexible Transportation Service for the Optimization of a Fixed-route Public Transport Network

In this paper, a flexible transportation service is proposed for a medium-sized city. By reviewing the literature of demand services, an algorithm solving the static multi-vehicle dial-a-ride problem with time windows and a fixed fleet of vehicles is developed and evaluated. Our contribution focuses on customers who specify their origin time from strategically chosen bus stations of the fixed infrastructure. A flexible objective function is used to reflect the customer's quality of service and also the operator's cost. Finally, simulated datasets of up to 500 user's requests are tested and compared against the public transport service of the city giving insight of how well a demand service performs.

Integrated Management of Underground Space Center of Moscow Based on the Development of Metropolitan Objects

Examines distortions of spatial development of the city of Moscow and the resulting urban planning, transport, social problems of the Centre of the metropolis. It is concluded that the efforts made by the Government of Moscow measures may be insufficient without strategic direction orientation of integrated urban underground space utilizing the potential of the city and especially its central zone. Reviewed the background and direction through the development of urbanization of underground objects. Provides suggestions for the justification and the preparation of a new master plan for the city, improve other instruments of urban management. Also provides specific recommendations for the optimization of the underground transport network in the central part of the city by embedding new stations on existing radial lines and justify slopes of underground, taking into account the geological conditions (with the creation of 3D models for this purpose). The basis of urban planning should become a principle of consideration of underground space as an integrated resource land. Proceeding from it, on an example of underground objects (like infrastructural skeleton of the city) are creating a spatial direction underground-ground systems, as well as improving their energy efficiency and utilization of recoverable materials. It is concluded that, despite the complexity of the tasks, their solution (with proper organization in the system of State Administration) is possible. It significantly will contribute to the achievement of the declared goal of sustainable development of the Russian capital.

The backbone transportation network optimization problem of air express based on scale economies

The backbone transportation network optimization problem of air express based on scale economies

OPTIMAL TEMPORAL PATH ON SPATIAL DECAYING NETWORKS

We introduce temporal effect to the classical Kleinberg model and study how it affects the spatial structure of optimal transport network. The initial network is built from a regular d-dimensional lattice added by shortcuts with probability p(rij) ∼ rij-α, where rij is the geometric distance between node i and j. By assigning each shortcut an energy E=r·τ, a link with length r survives within period τ, which leads the network to a decaying dynamics of constantly losing long-range links. We find new optimal transport in the dynamical system for α=3/4 d, in contrast to any other result in static systems. The conclusion does not depend on the information used for navigation, being based on local or global knowledge of the network, which indicates the possibility of the optimal design for general transport dynamics in the time-varying network.

Lévy Walk Navigation in Complex Networks: A Distinct Relation between Optimal Transport Exponent and Network Dimension.

We investigate, for the first time, navigation on networks with a Lévy walk strategy such that the step probability scales as pij ~ dij–α, where dij is the Manhattan distance between nodes i and j, and α is the transport exponent. We find that the optimal transport exponent αopt of such a diffusion process is determined by the fractal dimension df of the underlying network. Specially, we theoretically derive the relation αopt = df + 2 for synthetic networks and we demonstrate that this holds for a number of real-world networks. Interestingly, the relationship we derive is different from previous results for Kleinberg navigation without or with a cost constraint, where the optimal conditions are α = df and α = df + 1, respectively. Our results uncover another general mechanism for how network dimension can precisely govern the efficient diffusion behavior on diverse networks.

Оцінка параметрів лісотранспортної мережі у гірських лісах (на прикладі ДП «Осмолодське лісове господарство»)

Здійснено аналіз вітчизняних нормативних документів з інвентаризації лісових автодоріг. Представлено результати досліджень мережі лісових автомобільних доріг у ДП “Осмолодське лісове господарство”. Польові роботи полягали у встановленні місця розташування лісових автодоріг, параметрів і технічного стану їх дорожнього полотна та штучних споруд. Загальна довжина лісових автодоріг становить 182,97 км, з них 93,2% проходить по землях державного лісового фонду. Найбільша кількість доріг і відповідно їх протяжність наявна у передгірних лісництвах тоді як у гірських лісництвах є одна або кілька лісових доріг. Середня густота доріг, що проходять по території лісового фонду, становить 0,28 км на 100 га. Задовільний стан мають 85,6% лісових доріг, а дороги, які непридатні для проїзду лісовозного транспорту та потребують капітального ремонту, становлять 3,2%.

An optimization model to solve skidding problem in steep slope terrain

Abstract Designing an optimal off-road transportation network to allow access of logging systems to harvest sites is an important task in operational harvest planning. To address this issue, we have designed two variants of the capacitated network flow problem based on an integer programming (IP) approach with two sets of inter-dependent decisions. One set of decisions involves finding a feasible k -tree path network through segment linkages (routing flow) at a minimum variable cost, while another attends to the schedule of an even wood flow to the landing location(s) (transporting flow), within the scope of operational planning horizon. The mathematical models are then linked to a heuristic algorithm to identify the landing locations at the parcel level. The models were applied to a 680 ha area in the highlands of the Hyrcanian forests, in the north of Iran. The new formulation solved the problems using binary decision variables to represent transport of saw-logs from timber entry nodes to destination(s) by use of a ground-based machine skidder system. Then, the model uses continuous decision variables to represent transport of wood fuel to the same destination(s) by use of an animal skidding system. The results showed that the skidding costs and the length of the designed skid-trails were different based on the skidding systems and the types of products desired. Even though the models could generate an optimal solution, both of them could not address the real isolated timber node problem, where there is no accessible pathway for a skidding operation. As a promising point, the second model (splittable, animal systems) could partially solve the temporarily isolated timber nodes problem, where the timber nodes were not accessible by ground-based machine skidder systems.

Failure of classical traffic flow theories: a critical review

We explain that the fundamental empirical basis for automatic driving, reliable control and optimization of traffic and transportation networks is the set of empirical features of traffic breakdown at a road bottleneck. We show why generally accepted traffic and transportation theories and models are not consistent with this empirical fundament of traffic science. In particular, these classical traffic theories are as follows: In turn, this can explain why dynamics network optimization and control approaches based on these classical traffic flow theories failed by their applications in the real world. We discuss why rather that the assumption about the existence of stochastic highway capacity, at any time instant there should be the infinite number of highway capacities within a range of the flow rate between a minimum capacity and a maximum capacity as assumed in three-phase theory introduced by the author. Because the assumption about the infinite number of highway capacities is consistent with the set of the fundamental empirical features of traffic breakdown at highway bottlenecks, this can be considered a theoretical fundament for the development of reliable automatic driving, control and optimization of vehicular traffic and transportation networks. We discuss briefly some features of the three-phase theory explaining the empirical fundament of transportation science.

The Variant Approach To The Optimization Of The Postal Transportation Network In The Conditions Of The Slovak Republic

Abstract The optimizing process of the postal transportation network can be based on several variables and on different infrastructures. The most commonly used variables for optimization are time and distance. This article is focused on the comparison of the results of the optimization process based on the time and distance variables in the conditions of the Slovak national postal operator. The different types of the underlying infrastructures (roads or railways) could be used for optimization based on the territory conditions. For the optimization, there has been used the p-median method, that describes the problem of locating P “facilities” relative to a set of “customers” in such a way that the sum of the shortest demand weighted distance between “customers” and “facilities” is minimized. In the conclusion, the article authors will formulate the rule for selection of the best optimization variables for the postal transportation network optimization.

A biologically inspired network design model.

A network design problem is to select a subset of links in a transport network that satisfy passengers or cargo transportation demands while minimizing the overall costs of the transportation. We propose a mathematical model of the foraging behaviour of slime mould P. polycephalum to solve the network design problem and construct optimal transport networks. In our algorithm, a traffic flow between any two cities is estimated using a gravity model. The flow is imitated by the model of the slime mould. The algorithm model converges to a steady state, which represents a solution of the problem. We validate our approach on examples of major transport networks in Mexico and China. By comparing networks developed in our approach with the man-made highways, networks developed by the slime mould, and a cellular automata model inspired by slime mould, we demonstrate the flexibility and efficiency of our approach.

Coal Transportation Network Optimization Model Based on Power Source Distribution

Coal is the important fuel and industrial raw materials in my country, and it accounts for 70% of total energy production and consumption in our country, and power plants’ coal consumption accounts for more than half of national total coal consumption. The research of electric-coal supply chain related to coal production place, coal transit place and consumption place (power plant). Due to there are many nodes like these three kinds coal transportation in the market, so the project that integrates every nodes into unified transportation optimization network has the function of reducing coal consumption and saving transportation costs. The paper constructs coal transportation analysis model, electric-coal supply and transportation path dynamic optimization model based on electric-coal transportation network analysis, and make effective analysis for choosing electric-coal transportation path. The paper also puts forward electric-coal supply chain optimization measures from electric-coal supply chain integration and ports building.

Simulation and Optimization Models of Steady-state Gas Transmission Networks

Managing a gas transport network is a complex problem because of the number of possibilities of routing the gas through the pipes. The most important aim in this kind of systems is to fulfill the demand within the pressure bounds, independently of its associated costs. However, in the present work some cost drivers are also taken into account by means of different objective functions in order to manage the network in an efficient way. This work deals with mathematical modeling and optimization of gas transport networks, where a two-stage procedure is proposed. In the first stage, optimization algorithms based on mathematical programming are applied to make some decisions (whether to activate compressor stations, control valves and other control elements) and gives an initial solution to the second stage. This last stage, which is based on control theory techniques, refines the solution to obtain more accurate results. Due to the reduced complexity in each stage, both can be solved within reasonable runtimes for relatively large gas networks. Based on the mathematical methods involved, a software called GANESOTM has been developed.

Parametrization of Random Vectors in Polynomial Chaos Expansions via Optimal Transportation

Polynomial chaos (PC) expansions are used for the propagation of uncertainty through dynamical systems as an alternative to Monte Carlo methods. Model parameters in a given dynamical system are assumed to have known expansions, which correspond to simple standard distributions, and one is usually interested in the polynomial expansion of the system solution. We are concerned with the problem of estimating the PC expansion of a parameter vector when only realizations from its distribution are given. To this end we apply ideas from optimal transportation theory and network optimization.

Composite goal methods for transportation network optimization

Lately the topic of multi-objective transportation network optimization has received increased attention in the research literature. The use of multi-objective transportation network optimization has led to a more accurate and realistic solution in comparison to scenarios where only a single objective is considered. The aim of this work is to identify the most promising multi-objective optimization technique for use in solving real-world transportation network optimization problems. We start by reviewing the state of the art in multi-objective optimization and identify four generic strategies, which are referred to as goal synthesis, superposition, incremental solving and exploration. We then implement and test seven instances of these four strategies. From the literature, the preferred approach lies in the combination of goals into a single optimization model (a.k.a. goal synthesis). Despite its popularity as a multi-objective optimization method and in the context of our problem domain, the experimental results achieved by this method resulted in poor quality solutions when compared to the other strategies. This was particularly noticeable in the case of the superposition method which significantly outperformed goal synthesis.

Evolving Transport Networks With Cellular Automata Models Inspired by Slime Mould.

Man-made transport networks and their design are closely related to the shortest path problem and considered amongst the most debated problems of computational intelligence. Apart from using conventional or bio-inspired computer algorithms, many researchers tried to solve this kind of problem using biological computing substrates, gas-discharge solvers, prototypes of a mobile droplet, and hot ice computers. In this aspect, another example of biological computer is the plasmodium of acellular slime mould Physarum polycephalum (P. polycephalum), which is a large single cell visible by an unaided eye and has been proven as a reliable living substrate for implementing biological computing devices for computational geometry, graph-theoretical problems, and optimization and imitation of transport networks. Although P. polycephalum is easy to experiment with, computing devices built with the living slime mould are extremely slow; it takes slime mould days to execute a computation. Consequently, mapping key computing mechanisms of the slime mould onto silicon would allow us to produce efficient bio-inspired computing devices to tackle with hard to solve computational intelligence problems like the aforementioned. Toward this direction, a cellular automaton (CA)-based, Physarum-inspired, network designing model is proposed. This novel CA-based model is inspired by the propagating strategy, the formation of tubular networks, and the computing abilities of the plasmodium of P. polycephalum. The results delivered by the CA model demonstrate a good match with several previously published results of experimental laboratory studies on imitation of man-made transport networks with P. polycephalum. Consequently, the proposed CA model can be used as a virtual, easy-to-access, and biomimicking laboratory emulator that will economize large time periods needed for biological experiments while producing networks almost identical to the tubular networks of the real-slime mould.