不确定型层次分析法在桥梁综合评估中的应用研究

采用确定型层次分析法评估桥梁状态,存在指标的不确定性和模糊性。而利用不确定型层次分析法进行桥梁结构的多级模糊综合评估,建立桥梁的安全性评估模型及指标体系,运用不确定型权重判断矩阵和区间相离度概念,建立桥梁状态综合评估的单目标模型,求解区间权重的最优值,利用等级隶属度函数得出桥梁的评估等级。并通过实例证明不确定型层次分析法在桥梁状态综合评估中的可行性。     

Network structure and travel patterns: explaining the geographical disparities of road network vulnerability

Inevitably, links in the road network are sometimes disrupted because of adverse weather, technical failures or major accidents. Link closures may have different economic and societal consequences depending on in which regions they occur (regional importance), and users may be affected differently depending on where they travel (regional exposure). In this paper we investigate in what way these geographical disparities depend on the road network structure and travel patterns. We propose aggregate supply-side (link redundancy, network scale, road density, population density) and demand-side (user travel time, traffic load) indicators and combine them in statistical regression models. Using the Swedish road network as a case study, we find that regional importance is largely determined by the network structure and the average traffic load in the region, whereas regional exposure is largely determined by the network structure and the average user travel time. Our findings show that the long-term vulnerability disparities stem from fundamental properties of the transport system and the population densities. Quantitatively, they show how vulnerability depends on different variables, which is of interest for robust network design.     

Overall safety performance of the air traffic management system: Indicators and analysis

Defining means to assess safety performance and delve into their causes is one of the current and future challenges of the ATM sector. Following the experiences of the Aerospace Performance Factor by FAA and EUROCONTROL, this research aims to apply the Analytic Hierarchy Process (AHP) in order to build synthetic and user-friendly safety-related indicators. Through the analysis and combination of the safety events over time (accidents, incidents and issues), this model will pinpoint critical situations and will address the interventions of the decision makers.     

Towards an objective decision-making framework for regional airport site selection

Airport site selection requires consideration of several criteria constrained by complicated trade-offs. Airport literature and practice provide valuable insights in terms of influencing factors and multicriteria assessment methods, at the pace that reported siting processes follow non uniform decision-making structures. Current developments in geoinformation unveil a valuable opportunity of development of a structured methodology in the field of airport siting. Brazilian public sector decision-makers recognize that such methodology has the potential to improve the allocation of federal budget for new regional airports, in terms of implementation time and political friction. This research proposes a methodology termed MESA - Metodologia de Escolha de Sítios Aeroportuários (in Portuguese, Airport Site Selection Methodology). The purpose of MESA is to be sound under technical grounds and at the same time provide a more objective decision-making process. The proposed methodology consists of 4 phases: i) literature review of airport site selection criteria; ii) criteria systematization; iii) setting up of eliminatory criteria and their thresholds; and iv) setting up of scoring criteria and of an approach for their quantification. Eliminatory criteria reduce the original screening area, while scoring criteria are used for ranking purposes. MESA combines GIS (Geographic Information System) and classic AHP (Analytic Hierarchy Process) with direct assessment of alternatives through specific techniques. So far, the methodology has been applied to two real cases in the Brazilian context. In addition to effectively reducing subjectivity in airport site location decision, MESA has been demonstrating to be a powerful tool for mitigating environmental and social impacts associated to airport site selection. MESA is designed in such a way that simplifies improvements and adaptations, making it widely applicable.     

改进灰色关联分析法在物流园区选址中的应用

通过对物流园区选址的影响因素和物流园区选址常用的方法进行了具体的分析,将层次分析法和灰色关联分析法结合成改进灰色关联分析法,对物流园区的选址问题进行评价,从而得到最佳的物流园区建设方案。并通过实例说明该方法的有效性,能很好地解决物流园区的选址问题。     

Safety classification using GIS in decision-making process to define priority road interventions

Given the current economic situation of the Portuguese municipalities, it is necessary to identify the priority investments in order to achieve a more efficient financial management. The classification of the road network of the municipality according to the occurrence of traffic accidents is fundamental to set priorities for road interventions. This paper presents a model for road network classification based on traffic accidents integrated in a geographic information system. Its practical application was developed through a case study in the municipality of Barcelos. An equation was defined to obtain a road safety index through the combination of the following indicators: severity, property damage only and accident costs. In addition to the road network classification, the application of the model allows to analyze the spatial coverage of accidents in order to determine the centrality and dispersion of the locations with the highest incidence of road accidents. This analysis can be further refined according to the nature of the accidents namely in collision, runoff and pedestrian crashes.     

Towards a theory of decoupling: degrees of decoupling in the EU and the case of road traffic in Finland between 1970 and 2001

Traditionally, the transport literature reflects the view that traffic volumes, road traffic volumes in particular, are coupled with Gross Domestic Product (GDP). Recently published literature also argues that the carbon dioxide (CO₂) emissions from transport, passenger cars in particular, have not shown any decoupling from transport volumes for some years. This article presents a theoretical framework for decoupling, defining the difference between decoupling, coupling and negative decoupling. These are further broken down to weak, strong and expansive/recessive degrees of decoupling, laying emphasis on the absolute increase or decrease of the variables. The result section presents data of the development of the relationships between GDP, traffic volumes and CO₂ emissions from transport in the EU15 countries between 1970 and 2001, including the special case of Finnish road traffic. The aggregate EU15 data show a change from expansive negative decoupling to expansive coupling regarding passenger transport, and from weak decoupling to expansive negative decoupling regarding freight transport. Weak decoupling of transport CO₂ emissions from GDP could also be observed. Weak decoupling of all the three aspects (freight, passenger and CO₂) could be seen in the UK, Sweden and Finland in the 1990s. In Finland, the statistics show weak decoupling of GDP from road traffic volume and strong decoupling of road traffic volume and CO₂ emissions from road traffic between 1990 and 2001. Four hypothetical explanations of the Finnish phenomenon are put forward in this article: policy towards sustainable mobility, green urban lifestyle, increasing income differences, and statistical misinterpretation. Each explanation is backed up with some quantitative evidence in observable trends in Finland during the 1990s.     

The effects of area-wide road speed and curvature on traffic casualties in England

Transport provides a range of benefits to society in terms of mobility, access and economic growth. There are however negative impacts of transport, not least in terms of environmental degradation, damage to property, traffic accidents and loss of life. This paper focuses on road traffic accidents, the reduction of which is an important aim of transport policy world wide. The primary objective of this paper is to develop a series of relationships using spatially disaggregated area-level cross-sectional data between different traffic casualties, road traffic speed and road curvature by controlling for other contributing factors associated with area characteristics. The spatial units of the analysis are the 8019 census wards in England. Ward-level casualty data are disaggregated by severity of the casualty (such as fatalities, serious injuries and slight injuries) and by the severity of the casualty related to various road users.The results suggest that increased average speed within a ward is positively associated with total fatalities and serious injuries; and road curvature is found to be negatively associated with road accidents.     

Estimation of travel distances with the weighted ℓp norm: Some empirical results

The weighted ℓ_p or ℓ_k,p norm is used to model travel distances in road networks. The parameters k and p are computed from a sample of actual road distances taken from the geographical area of interest. During the computation, a goodness-of-fit criterion is computed and minimized when the best-fit values of k and p have been determined. Greatly improved results are obtained when the coordinate axes are rotated to account for any rectangular bias in the road network. In this paper, an examination of 17 diverse geographical areas shows that in every case, within a rotation arc of 90°, there are two points where the goodness-of-fit function is minimized. These two rotation points are approximately 45° apart; one results in a best-fit p value in the interval (1, 2) and the other results in a best-fit p value in the interval (2, ∞). This paper thus empirically confirms the double-bottom phenomenon which was hypothesized in a previous work. The superiority of the weighted ℓ_p norm as a distance predictor is also demonstrated.     

Analytic Hierarchy Process assessment for potential multi-airport systems – The case of Cape Town

This paper discusses the application of an Analytic Hierarchy Process (AHP) analysis for the assessment of a potential multi-airport development. The case study presented evaluates the potential introduction of a second airport in the City of Cape Town, which is currently served solely by Cape Town International Airport. With socioeconomic development, spatial planning, transportation improvement, environmental preservation and financial viability proposed as the main objectives of airport development, a survey of key stakeholders addressed the relative weighting of these criteria in the AHP. The multi-criteria decision-making assessment, as well as analyst judgement, concluded that the City of Cape Town should continue to utilise a single-airport system until passenger volumes per annum increase beyond the 27 Million Air Passengers per annum level.     

Exploring the relationship between truck load capacity and traffic accidents in the European Union

Applying econometric techniques to EU28 panel data and controlling for explanatory variables such as road types, we find that increased truck load capacity does not necessarily aggravate road traffic safety. Specifically, heavy trucks do not seem to be linked with greater numbers of traffic fatalities/accidents, medium trucks appear to be the worst performers in terms of fatalities, and light trucks seem to be the worst for accidents. In summary, our results clarify the complex relationship between truck load capacity and road safety, pointing to the existence of a negative correlation for accidents per capita and an inverse U-shaped curve for fatalities per capita.     

Spatial clustering of events on a network

In this paper a methodology is proposed to compute spatial concentrations of point-based events on a network. The distance along the network is used as a measure of the spatial closeness of events. The network is divided into statistical units, based on a random distribution of points of measurement and corresponding network segments, which are the statistical units of reference. For each segment a dangerousness index is computed which indicates the distance-weighted number of traffic accidents in the neighbourhood. The statistical significance of clusters of accidents is tested using a Monte Carlo simulation. The methodology is applied to traffic accidents to detect dangerous locations on the road network of the city of Brussels in Belgium.     

Estimating marginal external costs of transport in Delhi

This paper develops the model and methodology to estimate the marginal external cost of urban road transport, which is necessary for analysing optimal urban transport prices. Four major marginal external costs analysed in this paper include the marginal external costs for congestion, air pollution, road accidents and noise. The paper estimates the marginal external costs for cars and buses in peak and off-peak periods for Delhi urban agglomeration for the year 2005.     

Using accessibility indicators and GIS to assess spatial spillovers of transport infrastructure investment

This paper proposes a methodology to measure spatial spillovers of transport infrastructure investment and to monetize them by distributing the costs of the infrastructures envisaged according to the regional distribution of the potential accessibility benefits. We use a transport master plan (the Spanish “Plan Estratégico de Infraestructuras y Transporte” 2005–2020, PEIT) as a case study for applying our methodology. In order to calculate and map regional spillovers, economic potential values are computed using network routines in a Geographic Information System (GIS) by comparing two scenarios: firstly, the scenario PEIT 2020; and secondly the scenario which includes the improvements envisaged for the year 2020 in all the regions except the region whose spillover effects are being analyzed. The differences between these two scenarios represent the potential spatial spillover effects of this region on the rest of the regions. This procedure is repeated for each of the Spanish regions in order to calculate a matrix of inter-regional spillovers in economic potential units. In a second step, this matrix is monetized by distributing the costs of the investment in infrastructures envisaged in the region according to the regional distribution of the economic potential benefits. This inter-regional matrix of investments flows characterizes the “inner”, “export”, and “import” values of each of the regional road investments. Subtracting from the direct investment the exports to other regions and adding the imports from other regions, an estimation of the real investment of the plan in each region taking into account all the spillover effects is obtained. This value can be compared with the direct investment in the region, analyzing whether one region has more or less direct investment than real. The proposed methodology makes it transparent which regions benefit more from national transport investment irrespective of where the investment occurs. The spillover matrix can be a valid instrument, especially in federal states or in the case of transnational projects, in the field of regional economics because it offers very useful information for both planners and policy makers.     

How large is the gap between present and efficient transport prices in Europe?

In this paper, we analyse the gap between present transport prices and efficient transport prices. Efficient transport prices are those prices that maximise economic welfare, including external costs (congestion, air pollution, accidents). The methodology is applied to six urban and interregional case studies using one common optimal pricing model. The case studies cover passenger as well as freight transport and cover all modes. We find that prices need to be raised most for peak urban passenger car transport and to a lesser extent for interregional road transport. Optimal pricing results for public transport are more mixed. We show that current external costs on congested roads are a bad guide for optimal taxes and tolls: the optimal toll that takes into account the reaction of demand is often less than one third of the present marginal external cost.     

Policy integration: What will it take to achieve more sustainable transport solutions in cities?

There has been a rhetorical shift in paradigm from predict and provide for road transport to one which addresses sustainable mobilities. This paper explores the organizational and institutional issues of policy integration and the implementation mechanisms which could bring about a sustainable transport system predicated on the reduction of CO₂ emissions and non-renewable resource use and which produces more socially equitable outcomes. The paper first outlines the English policy context in terms of responsibilities, powers and resources available to local transport planners, and identifies the tools of government that can be more efficiently applied to effect a more sustainable transport system which specifically reduces CO₂ emissions. A snapshot of transport decision-making in five local transport authorities in England is presented, using a case study methodology, which explores the joint working practices of practitioners in five public policy sectors that influence accessibility patterns. The case study highlights the norms and values of the local public administrators who affect local transport mobility and how they in turn are hindered both by the rigidity of central government direction and an insufficiency of implementation tools.     

Profiling road transport activity: Emissions from 2000 to 2005 in Ireland using national car test data

This work describes a methodology for determining the average vehicle kilometres travelled by the private national car fleet in Ireland and estimating the disaggregated CO₂ and NO_x emissions from private vehicles in the Irish road transport sector for the period 2000–2005 using national car test records. The developed methodology facilitates the calculation of greatly improved estimates for vehicle kilometres under a range of constraint variables and thereby enables the disaggregated analysis of specific vehicle fleet groups and their associated activity patterns to support evidence-based policy development. The results indicate that while older vehicles are contributing significantly to car NO_x emissions; newer cars produce a higher share of CO₂ emissions than older cars in the vehicle fleet.     

Spatial interpolation of traffic counts based on origin–destination centrality

This paper presents a new method to estimate Annual Average Daily Traffic. Often traffic volumes are estimated based on roadway characteristics, such as number of lanes, speed limit, and adjacent land use. However, for many communities, especially small communities, these attributes are uniform across roadway types and therefore unable to adequately explain observed variation in traffic volumes. The new method uses novel explanatory variables that are intrinsically derived through a modified form of centrality, a network analysis metric that quantifies the topological importance of a link in a network. The new approach requires minimal data collection and is easily executed using a geographic information system. The case study showed high quality results (out-of-sample validation R² = 0.95). The new approach can be used for various activities related to transportation planning and investment decision making.     

A study on travelers' transport mode choice behavior using the mixed logit model: A case study of the Seoul-Jeju route

This study is to analyze passengers' choice of the mode of transportation when air transportation is in competition with high speed rail (HSR). The Seoul-Jeju route analyzed as an empirical case study, in which the construction of an undersea tunnel to connect Seoul and Jeju city by HSR has been considered. The study also included two new variables, ‘safety of transportation’ and ‘availability of duty free shopping’ in addition to traditional transport choice variables such as travel time, travel costs and frequency of service to reflect special characteristics of the market. As data gathering tools, SP techniques and mixed logit model, for analytical methodology, were utilized. The authors found that the goodness of fit of the models was improved with new variables. The models also showed that the characteristics of business passengers and leisure passengers in choosing the mode of transportation were different. Business passengers were apt to choose a safety secured mode of transportation regardless of fare while leisure passengers preferred to use duty free shops more than business passengers.     

Lessons from travel planning and road user charging for policy-making: through imperfection to implementation

In 1978 Gunn published a seminal paper which explained why implementation of policy is so difficult. The paper set out 10 conditions, which should be satisfied if perfect implementation is to be achieved. Whilst it is clear that perfect implementation is not possible in the real world, and Gunn has subsequently been criticised for his ‘top-down’ approach to decision-making, these conditions do, nonetheless act as an effective framework through which to evaluate good practice in the implementation of urban transport policy instruments. Two urban transport policy instruments, which form an increasingly important element of the Government's strategy in the UK for reducing the demand for private transport as set out in a New Deal for Transport (DETR, 1998), are travel plans and road user charging. Travel plans are a relatively recent policy instrument in the UK and seek to reduce trips to work by car by providing, through individual employers, a targeted, integrated package of incentives and disincentives to influence commuters' choice of mode of travel to and from the workplace. Road user charging, whereby motorists are charged for the road space they use in urban areas, seeks to reduce the congestion problem via the price mechanism, and has a longer history in the UK. To date the implementation of travel plans in the UK has been more widespread than that of road user charging. It is fair to say, however, that the widespread implementation of both urban transport policy instruments is a complex and sensitive area for decision-makers.The aim of this paper is firstly, to analyse travel plans and road user charging in the UK with respect to the conditions for perfect implementation put forward by Gunn and secondly, to highlight the elements of good practice, pertinent to the implementation of road user charging, in the process of the implementation of travel plans. Overall, the paper uses Gunn's theoretical framework as a basis for recommendations for better decision-making that will aid the wider implementation of both travel plans and road user charging internationally.