Network models in traffic management and control

Abstract

The context for network modelling in traffic management and control is described in terms of the current area‐wide nature of traffic management and the range of objectives to which it can contribute. Representation of a road system and traffic management measures in terms of nodes and links and parameters associated with them is described. It is shown that the pattern of traffic has to be represented not only in terms of flows on links of the network but also in terms of numbers of movements per unit time between points of entry to and points of exit from the area being modelled. In modelling so far, these numbers of movements are regarded as given, but the routes taken are estimated by traffic assignment. Models can so far be used for comparison of a range of given schemes and for optimization of traffic control within a scheme. Variation over time is a central feature of the modelling, and this requires the use of time‐dependent queueing theory, and the specification of numbers of movements for a succession of periods of between 10 and 30 minutes. Theoretical approaches to the resulting problems of modelling and optimization are discussed, and the ways in which these are supplemented by heuristic methods in currently available models is described. Some requirements‐for further research are outlined.     

Individual versus mass transportation: feasibility of substitution

This paper is addressed to the question of social costs and social benefits (primarily environmental) which might derive from a large‐scale substitution of so‐called mass‐transit for the present, largely private, system of automotive transportation. Energy consumption and emissions are compared for the two basic alternatives and several variants. Varying degrees of physiological tolerance to pollutants are taken into account, in an attempt to develop comparable weight‐factors for different types of emissions. It is suggested that if automobiles succeed in meeting the 1975/76 emission standards set by the Clean Air Act of 1970, rail rapid transit will probably offer no advantage (in environmental terms) unless electric power is available from virtually non‐polluting sources (e.g., natural gas or nuclear plants). Economic implications of large‐scale substitution are examined, and it is noted that such substitution would involve major restructuring of our society as a whole. However, more intensive use of mass transit in central cities, possibly in conjunction with various measures to discourage the use of private automobiles in very congested areas is feasible and likely.     

Evacuation Modelling in the United States: Does the Demand Model Choice Matter?

Abstract

This paper reviews the literature on the evacuation demand problem, with an emphasis on the impact of various modelling approaches on network‐wide evacuation performance measures. First, a number of important factors that affect evacuee behaviour are summarized. Evacuation software packages and tools are also investigated in terms of the demand generation model they use. The most widely used models are then selected for performing sensitivity analysis. Next, a cell‐transmission‐based system optimal dynamic traffic assignment (SO‐DTA) model is employed to assess the effects of the demand model choice on the clearance time and average travel time. It is concluded that evacuation demand models should be selected with care, and policy makers should make sure the selected demand curve can replicate real‐life conditions with relatively high fidelity for the study region to be able to develop reliable and realistic evacuation plans.     

Estimating the long-term effects of different passenger car technologies on energy/fuel consumption and emissions of greenhouse gases in Europe

Abstract

A stated preference (SP) experiment of car ownership was conducted in Mumbai Metropolitan Region (MMR) of Maharashtra in India. A full factorial experiment was designed to considering various attributes such as travel time, travel cost, projected household income, car loan payment and servicing cost. Data on 357 individuals were collected which resulted in 3213 observations for the calibration of the work trip and recreational trip car ownership models. The car ownership alternatives considered 0, 1 and 2 cars. A multinomial logit framework was used to develop the car ownership model taking the household as a decision unit. The specification and results of the SP car ownership model are discussed. The observed and predicted values matched reasonably when the validity of the SP car ownership model was tested against revealed preference (RP) data. The car ownership models developed in this study exhibit a satisfactory goodness of fit. It is concluded that the SP modelling approach can be successfully used for modelling car ownership decisions of households in developing countries.     

Restructuring the Greek Railways: Current Progress and Evaluation of Alternative Schemes

Abstract

This paper presents the rationale, the method, and the alternative choices in the process of restructuring the Hellenic Railways Organisation (OSE). The most likely alternative structures regarding ownership and management issues of the new entities that will inherit the old OSE organization, and discusses the strategic implications of these alternatives are discussed. A critical view of the process of Greek railway reform and the evaluation results of the alternative organizational structures for the new situation are presented. It first presents the current experience in European Union and other countries of Europe, and the relative position of the Greek railways vis‐à‐vis the most common practices. The most likely options for the new organizational structure are presented which will result from the application of the European Union Directives and the Greek Law 2671/98 for the reorganization of the Greek railways. Based on a more detailed presentation of expected income and expenditures (i.e. economic viability) of the alternatives, a structure and a roadmap to these reforms is recommended for a successful and, above all ‘implementable’, reform of the Greek railways under the current conditions. Finally, the process for change and restructuring is described in terms of the basic principles and procedures that should be followed, and in terms of the necessary steps and procedures for the transition from the current to the new situation.     

Traffic models for goods,service and business movements to manufacturing establishments

This paper is concerned with a problem area of increasing interest, namely the traffic characteristics of specific generators located on non‐residential land use. It concentrates on the problem of modelling traffic generation for goods, service and business movements at the manufacturing establishment. Firstly the contributions of earlier researchers are reviewed in the context of factors which have been considered important. Then a further study conducted by the author in Sheffield and in Manchester, England, is described. This study considers more rigorously than hitherto the questions of similarities in trip rates over different manufacturing activities and geographical areas, and of the choice of explanatory variables. Comparison of regressions is used to formalize indications of similarities in trip rates, and analysis of variance for choosing the most satisfactory explanatory variables. The study provides evidence of similarity in trip rates over seven different manufacturing activities and two geographical areas. It also shows distinctions between different non‐work traffic types in the extent of similarities in trip rates over different manufacturing activities and in explanatory variables for traffic generation relationships. Regarding the latter it is concluded that it is not possible to model accurately such traffic movements on the basis of explanatory variables which are normally available. Instead trip rates should be expressed in simple mathematical terms and should be based on large data populations. The study also makes contributions on peak flow factors for the actual design of facilities of manufacturing establishments. These findings and others are discussed in the context of the work of earlier researchers. Finally conclusions are drawn and guidance offered for future work into this problem.     

A planning model for multiple‐mode transportation system operations

The problem of generating a set of “good” transportation alternatives during the early and intermediate stages of transportation planning is addressed in this paper. A linear programming model of a multi‐modal transportation system is developed. The model is run interactively to determine optimal operating levels for all modes for various transport policy decisions. The model described is a component of a composite network generation model incorporating dynamic changes. The linear programming component determines optimal operating policies for given points in time. The composite model incorporates these in a dynamic programming framework to determine optimal staged investment policies over several time periods.     

Inverse discrete choice modelling: theoretical and practical considerations for imputing respondent attributes from the patterns of observed choices

ABSTRACT

The growing availability of geotagged big data has stimulated substantial discussion regarding their usability in detailed travel behaviour analysis. Whilst providing a large amount of spatio-temporal information about travel behaviour, these data typically lack semantic content characterising travellers and choice alternatives. The inverse discrete choice modelling (IDCM) approach presented in this paper proposes that discrete choice models (DCMs) can be statistically inverted and used to attach additional variables from observations of travel choices. Suitability of the approach for inferring socioeconomic attributes of travellers is explored using mode choice decisions observed in London Travel Demand Survey. Performance of the IDCM is investigated with respect to the type of variable, the explanatory power of the imputed variable, and the type of estimator used. This method is a significant contribution towards establishing the extent to which DCMs can be credibly applied for semantic enrichment of passively collected big data sets while preserving privacy.     

Mobility evaluation for urban public transportation

Summary

This paper has reported on a study of relative opportunity—not absolute opportunity. Minimum absolute standards for mobility or accessibility are difficult to justify. Some additional study into the development and application of absolute mobility standards may be warranted.

The application of the mobility evaluation model has primarily focused upon a corridor line‐haul system. Conclusions suggest that such a system will not markedly improve existing transit mobility levels in either the peak hour or the off‐peak. The experimental work has verified this conclusion, and more importantly, it has detailed quantitatively the exact levels and spatial distribution of mobility improvements. However, this study does not include a comprehensive analysis of all methods of mobility enhancement, nor does it undertake a comparison of alternative means of mobility improvement. Certainly other methods to improve access to opportunities should be explored before policy considerations are finalized. These methods include other transit solutions, land use alternatives, socio‐economic policies, and other‐mode transportation alternatives. The accessibility technique and mobility indices approach appears to have general applicability in the analysis of optimal strategies for system evaluation.

Of interest is an examination of alternative feeder transit systems to the corridor line. Additional research with the model might point out the maximum mobility effects expected through improved collector service in the suburbs, with corridor line‐haul to the CBD.

The indices are also readily available for a comparison of mobility patterns for different urban areas. Application of the program to transit and socio‐economic data for a set of cities would yield an indication of the relative mobility levels provided. Such data might be considered as an evaluation criterion for future transit funding by federal officials.

In addition, the model is currently being considered by UMTA as a tool to aid in the evaluation of the equitable distribution of transit system benefits as defined in Title VI of the Civil Rights Act of 1964.²⁵ The mobility output would serve as an indicator of the levels‐of‐service provided to certain disadvantaged urban groups. For this application the computer model is being altered to achieve compatability with the Transportation Planning System (UTPS) computer model package developed by UMTA.     

Traffic Performance Models for Dynamic Traffic Assignment: An Assessment of Existing Models

Abstract

This paper provides a review of the traffic performance models for dynamic traffic assignment (DTA) and it identifies the strength and weakness of existing models. Requirements for traffic performance models are identified and various forms of existing traffic performance models for DTA are reviewed and analysed according to the requirements. Non‐linear travel time models are shown to have some deficiencies that make them unsuitable for the analysis of time‐varying transportation networks. Even though linear‐type travel time models are identified as good candidates for the analysis of dynamic transportation networks, they have limitations from the practical point of view that travel time increases only linearly with the amount of traffic on the link. This poses a dilemma and it seems to be one whose resolution is an imminent precondition for DTA modelling to progress in a way that is both theoretically coherent and plausible in practical terms.     

Road Safety Trends at National Level in Europe: A Review of Time-series Analysis Performed during the Period 2000–12

Abstract

This paper presents a review of time-series analysis of road safety trends, aggregated at a national level, which has been performed in the period 2000–12 and applied to European national data sets covering long time periods. It provides a guideline and set of best practices in the area of time-series modelling and identifies the latest methods and applications of national road safety trend analysis in Europe. The paper begins with the methodological framework adopted for aggregate time-series modelling that will be considered, and then discusses a number of relevant applications to long-period data aggregated at the national level, whether for countries alone, or for groups of countries. Some analyses, which were performed at the disaggregated level, are also provided, as they are being used more and more. Finally, the paper summarizes and discusses the significant changes in aggregate road safety trend analysis which occurred during the period and provides recommendations for continuing these research efforts.     

Parking restraint policy and urban vitality

The aim of the paper is to examine whether parking restraint policies may have impacts on the economic vitality of urban centres. Literature from empirical, attitudinal and modelling studies is reviewed within a structure based around a conceptual framework of parking impacts. The search for relevant material was undertaken both for the UK and overseas, but the discussion and conclusions were related to the UK context. Original modelling was undertaken and is reported here. This review found that as parking restraint policies have not been previously implemented with consistency or longevity, there is a lack of direct evidence, given that land-use impacts typically involve a long-term response. Furthermore, different methods of examining impacts have come to very different conclusions. Attitudinal evidence suggests that there is a high level of sensitivity to parking provision, whereas aggregate statistical studies tend to find only a weak relationship. The reasons underlying these differences are discussed. Land-use/transport models show impacts if there is sufficient change in generalized cost, although the spatial distribution of impacts, and impacts by household or employment disaggregation, vary considerably. Given the inconclusive nature of the evidence to date, only tentative policy implications can be drawn. Recommendations for further research are outlined, both for empirical study and for model enhancements.     

Calculation of external costs for freight transport

Abstract

The negative impacts of transport are in general associated with costs. These costs are usually denoted as ‘external costs’ or ‘externalities’. This paper presents a tool for calculating external costs for freight transport together with its application to a number of case studies. The categories considered include: air pollution, greenhouse gases, noise, accidents and congestion. Results are presented for a number of different transport alternatives as total costs and divided into categories. The uncertainties in the results are discussed. The assessment of these costs is essential for predicting future transport costs.     

Gantry crane operations to transfer containers between trains: A simulation study of a Spanish terminal

Freight transfer operations are critical in combined transport networks. In this paper a simulation model and modelling approach to the transfer of cargo between trains at rail terminals is presented. The model is used to study the Port-Bou terminal, the main intermodal terminal at the Spanish-French frontier. Four different gantry crane operation modes to interchange containers between trains are evaluated. These operation rules are tested in several scenarios to examine the critical factors of the system and the best operation rule for each situation. Latest generation software is used to develop the model that incorporates modular programming and enhanced graphic systems for output representation. It allows a dynamic display of the simulated system and, likewise, the possibility of developing modules that can be reused in other studies. The research shows how simulation can be a useful planning tool in the rail transportation context.     

Examining the Impacts of Residential Self‐Selection on Travel Behaviour: A Focus on Empirical Findings

Abstract

Numerous studies have found that suburban residents drive more and walk less than residents in traditional neighbourhoods. What is less well understood is the extent to which the observed patterns of travel behaviour can be attributed to the residential built environment (BE) itself, as opposed to attitude‐induced residential self‐selection. To date, most studies addressing this self‐selection issue fall into nine methodological categories: direct questioning, statistical control, instrumental variables, sample selection, propensity score, joint discrete choice models, structural equations models, mutually dependent discrete choice models and longitudinal designs. This paper reviews 38 empirical studies using these approaches. Virtually all of the studies reviewed found a statistically significant influence of the BE remaining after self‐selection was accounted for. However, the practical importance of that influence was seldom assessed. Although time and resource limitations are recognized, we recommend usage of longitudinal structural equations modelling with control groups, a design which is strong with respect to all causality requisites.     

Electric vehicles and the urban environment

Abstract

Due to the increased traffic volume, especially in urban areas, cars have become the dominant source of atmospheric pollution. Actions taken to limit the pollution have not been able to counteract the polluting effect of this increase in cars. Limited petroleum resources have initiated the search for alternative fuels for vehicles. These alternatives, except for hydrogen and electricity, will however only give a limited decrease of pollution and for some components, such as aldehydes, the pollution will increase.

Electric vehicles are attractive from both energy and environmental points of view and substantial development programmes are devoted to high energy density batteries which are expected to increase the range and market for this alternative.

The scope of this paper is to compare the overall atmospheric pollution for electric vehicles with the corresponding figures for internal combustion engined (ICE) vehicles using either gasoline or such alternatives as methanol and liquid petroleum gas.

It is shown that the total atmospheric emission for electric vehicles, including what is produced from the power plant, would on a per mile basis be 20% of the comparative figure for an ICE vehicle meeting Californian legislation, which is among the most stringent in the world. For ground emission, which is the most important parameter regarding influence on man and environment the corresponding figure will be substantially lower. Also, the noise level for electric vehicles is radically lower than for cars with internal combustion engines.     

An assessment of the demand for new transport technology in Australia

This paper summarizes the constraints which a technological innovation in transport must satisfy if it is to achieve widespread application. The existing and likely future travel demands in Australia are reviewed, and for certain types of travel it is concluded that existing modes may become unsuitable or unacceptable. In these areas, it is possible that a new transport technology may find application. In all other areas, it is considered that existing modes, or their functional successors, will continue.

Five possible demand areas in which new transport technology may find application are identified. These are as follows:

1) High speed distribution systems may be introduced in Australian CBD's (Central Business Districts) within the next ten years. These may be progressively extended to provide radial public transport services to the CBD. It is also possible that these systems may eventually be extended to provide a dual‐mode capability in inner‐suburban areas as a partial alternative to freeway construction.

2) New town developments which may be introduced in Australia could include various forms of advanced transportation systems.

3) New aviation modes, possibly including short take off and landing aircraft operating from suburban airports may be introduced to cater for inter‐urban travel.

4) A demand‐responsive transport system to cater for the needs of the transport poor in urban areas may find limited application.

5) In the longer term, possibly by the turn of the century, an improved transport system capable of providing door‐to‐door service over the whole of an urban area and operating under a dual‐mode configuration appears to be possible. It probably would emerge from development of an incremental nature and eventually include the installation of a new technology in the then existing freeway and railway reservations in the city.     

Integrating GIS concepts into transportation network data structures

Transportation network data structures must be designed to meet the requirements of the analyses being conducted and must be compatible with the selected graphical user interface. Increasing interest in geographic information systems (GIS) and intelligent transportation systems (ITS) have further burdened the network data structure. It is possible to implement object oriented programming (OOP) technology to satisfy these needs, without making the data structure excessively complicated.

This paper shows how a well‐developed network data structure can incorporate major capabilities normally associated with stand‐alone GIS's. The design of a network data structure derives from both theoretical and practical considerations. A design of a network data structure, composed entirely of objects, is presented. Examples of its implementation, limitations, advantages, and possible extensions are drawn from experience with the General Network Editor (GNE).     

Dominance among alternatives in random utility models

In many discrete choice contexts the actual choice set, including the alternatives effectively perceived and considered by the decision maker, may substantially differ from the universal choice set, including all available alternatives: one of the most relevant examples within transport demand simulation is probably the choice of destination, wherein the universal choice set normally includes hundreds of traffic zones. In these cases, proper simulation of the choice set is crucial for correct simulation of the choice context.In this regard, our paper has two main objectives. The first is to give a general contribution to choice set modelling by extending and applying the concept of dominance among alternatives to the framework of random utility theory. The main result is the definition of a methodology for the generation of new dominance attributes, which can be used in choice set modelling. The second aim is to make a specific contribution to destination choice modelling: dominance attributes are defined from the above methodology and introduced into this choice context, and new spatial variables reproducing better knowledge of zones with a privileged spatial position are also proposed. Methodology and attributes are tested both on synthetic and on real data.     

Testing a Framework for the Efficiency Assessment of Road Safety Measures

Abstract

The objective of this research is to develop and test a framework for efficiency assessment of road safety measures and evaluate its use in decision‐making. An exhaustive review of standard methodologies and practices related to cost‐effectiveness and cost–benefit analyses is carried out for that purpose. Moreover, a number of case studies are performed, concerning the efficiency assessment of various road safety measures in different countries, covering different types of road safety measures (user‐, vehicle‐ or infrastructure‐oriented, policy or enforcement, etc.), ranging from national to local levels of implementation and including both ex ante and ex post evaluations. From the results conclusions are drawn on the efficiency of different road safety measures and the related determinants. Furthermore, the case studies reveal a number of methodology and data issues for which further research is required. The procedures and barriers involved in the use of efficiency assessment techniques at different levels of decision‐making are also highlighted by means of feedback received during and after the various case studies. On the basis of these results, a framework for the promotion, implementation and evaluation of efficiency assessment in road safety decision‐making is proposed. A particular set of recommendations is also presented regarding the treatment of barriers (fundamental, institutional or technical) within the efficiency assessment itself and the related decision‐making process.