Michael A P Taylor

Integration of the global positioning system and geographical information systems for traffic congestion studies

Abstract The Transport Systems Centre (TSC) has developed an integrated Global Positioning System (GPS) – Geographical Information System (GIS) for collecting on-road traffic data from a probe vehicle. This system has been further integrated with the engine management system of a vehicle to provide time-tagged data on GPS position and speed, distance travelled, acceleration, fuel consumption, engine performance, and air pollutant emissions on a second-by-second basis. These data are handled within a GIS and can be processed and queried during the data collection (from a notebook PC in the vehicle) or saved to a file for later analysis. The database so generated provides a rich source of information for studies of travel times and delays, congestion levels, and energy and emissions. A case study application of the system is described focusing on studies of congestion levels on two parallel routes in a major arterial corridor in metropolitan Adelaide, South Australia. As part of these investigations, a discussion of the nature of traffic congestion is given. This provides both a general definition of traffic congestion and the discussion of a number of parametric measures of congestion. The computation of these parameters for the study corridor on the basis of data collected from the integrated GPS–GIS system is described. The GIS provides a database management platform for the integration, display, and analysis of the data collected from GPS and the in-vehicle instrumentation.

GLOBAL POSITIONING SYSTEMS IN THE TIME DOMAIN: HOW USEFUL A TOOL FOR INTELLIGENT VEHICLE-HIGHWAY SYSTEMS?

Abstract Much of the research and development work in intelligent vehicle-highway systems (IVHS) relies on the availability of methods for locating and monitoring vehicles (e.g. “probe vehicles”) in real time across a road network. This paper considers the use of the global positioning system (GPS) as one method for obtaining information on the position, speed and direction of travel of vehicles. It reports the results of a series of field studies, in which real-time GPS data were compared to data collected by an instrumented vehicle, under a range of physical and traffic conditions. The field studies and consequent data analysis provide a picture of the reliability and usefulness of GPS data for traffic monitoring purposes, and hence the possibilities for the use of GPS in IVHS projects. The use of GPS receivers tailored for mobile applications, and able to provide direct observations of vehicle speed and travel direction, coupled with database management using geographic information systems (GIS) software, was found to provide a reliable and efficient system for vehicle monitoring. Field data collection under “ideal” GPS conditions indicated that accurate speed and position data were readily obtained from the GPS. Under less favourable conditions (e.g. in downtown networks), data accuracy decreased but useful information could still be obtained. In addition, the conditions and situations under which GPS data errors could be expected were noted. The finding that it is possible to relate standard GPS signal quality indicators to increased errors in speed and position provides an enhanced degree of confidence in the use of the GPS system for real-time traffic observations.

TRAVELLING SMARTER DOWN UNDER: POLICIES FOR VOLUNTARY TRAVEL BEHAVIOUR CHANGE IN AUSTRALIA

This paper reviews the voluntary travel behaviour change programs adopted across Australia in recent times. These programs facilitate individuals and households in changing their travel behaviour through personal choice and individual action. The paper examines the issues relating to the various programs and discusses the techniques used and the results and evaluations. The behaviour change programs reported to date show consistent evidence that participating households make substantial reductions in their usage of private motor vehicles. Further, a range of non-transport benefits have been found, albeit at the local level. These benefits include changes in land use, social interaction, economic development, and health indicators. One consequence is that other government agencies, responsible for areas such as community development, health, environment, energy, public safety, planning and even education, have begun to form interests in the programs. Two key challenges have emerged: (1) the actual measurement tools are hard to implement or the changes are on a scale smaller than that at which measurement is usually made, and (2) the clients for travel behaviour change programs have to date been transport organisations for whom the only relevant outcome is travel change. Given that these projects may be of value to other interested organisations, it may be that ultimately travel behaviour change may be intimately linked with all aspects of community life, which could lead to greater change, and certainly to greater sustainability.

Using GPS to Measure Traffic System Performance

Traffic system performance can be measured in various ways, but from the user perspective, congestion is the major criterion. This article examines some novel uses of GPS in the measurement of vehicle speeds and travel times and their synthesis into measures of congestion and ultimately of the performance of the urban road system. The article also will discuss the integration of GPS-based congestion measures into an ITS framework, techniques for implementing a congestion-monitoring system, and implications for urban road system planners, managers, and users.

Transport Network Vulnerability: a Method for Diagnosis of Critical Locations in Transport Infrastructure Systems

Considerations of critical infrastructure are now a major concern in Australia as in many other countries. The concern stems from a variety of causes, including the state of development, condition and level of use of existing infrastructure systems, especially transport networks; difficulties associated with public sector provision of new infrastructure; publicprivate partnership arrangements for infrastructure provision; and perceptions of risks and threats to infrastructure from both natural disasters (e.g. floods, fire or earthquake) and from human malevolence such as acts of sabotage, war or terrorism. The Australian Federal Government has defined critical infrastructure as ‘that infrastructure which if destroyed, degraded or rendered unavailable for an extended period, will significantly impact on social or economic well-being or affect national security or defence’ (Attorney-General’s Department, 2003). A pertinent question is then how to identify critical locations in an infrastructure network. For example, the road transport network is large, wide and diverse in nature. Are there particular locations or facilities in that network where loss or degradation of certain road sections (links) will have significant impacts? How should such impacts be assessed?

Understanding traffic systems : data, analysis and presentation

Contents: Introduction: Introduction and context The traffic analysis process. Basic Traffic Theory: Basic traffic flow theory Theories of interrupted traffic flow Theories of area-wide traffic flow. Data Capture: Principles of survey planning and management Experimental design and sample theory Vehicle counting and classification surveys Traffic condition data Environmental impacts. Traffic Studies: Intersection studies Origin-destination and route choice studies Traffic generation and parking studies Road safety studies. Data Analysis and Modelling: From data to information Statistical analysis Statistical modelling. Appendix A: Statistical tables Appendix B: Database of vehicle speeds on residential streets References Index.

Travel through time: the story of research on travel time reliability

This paper provides a review of research on the concepts and application of travel time reliability and on the underpinning research on travel time variability. It charts the development of the topic from beginnings concerned with exploring the possible extent of variability in travel times through to the current interests in the specification of meaningful metrics for reliability, the inclusion of travel time reliability factors in traffic assignment and on ascribing economic valuations to travel time reliability for use in the economic appraisal of transport policies and projects. Travel time reliability is now recognised as a major determinant of travel behaviour and as an important performance measure for transport systems operation. Much has been achieved in understanding the symptoms and causes of variability in travel times. Yet the definitions are still not completely clear, and as a consequence the measurement and assessment of travel time reliability is still open to interpretation. Relationships between traffic congestion and reliability are inferred, and in more recent times the influence of ‘extreme events’, including weather events, on reliability has become an important research topic. The paper reviews the current situation, and provides ideas for future research.

A parking model hierarchy

The last decade has seen considerable developments in computer assisted design procedures which enable planners to investigate the impacts of changes in the transport system. These developments have become more available to analysts through the introduction of microcomputers and computer graphics. Unfortunately, the impacts of parking on the transport have not been incorporated explicitly in many of these models since their prime concern is the movement of traffic. Parking system design and policy analysis can, however, benefit greatly from these developments in computer technology and availability. The design of parking systems can be improved and the investigation of policy impacts can be trialed or refined prior to their introduction using microcomputer packages. This paper outlines some developments in these areas. More specifically, it outlines a hierarchy or microcomputer models and information systems that can investigate parking policy and study the “level of service” provided by parking systems.

An Accessibility Framework for Evaluating Transport Policies

This paper describes how most measures of accessibility lack the capability to evaluate the impacts of transport policies that can directly influence travel decisions. The major reason for this is that many measures of accessibility do not take into consideration enough of the factors that can be influenced by policies. Among such factors are those related to the attributes of individuals who have undertaken travel for the purpose of accessing activities. The paper argues that the focus of such measures should be on accessibility for individuals to activities rather than purely being a property of locations since the accessibility of a location does not necessarily reflect the true accessibility of an individual to that destination. Although accessibility to destinations is important, it is only part of a person’s accessibility. The focus should be on accessibility to activities that can be satisfied by a number of destination alternatives. The paper describes an accessibility framework that combines a number of classical measures of accessibility using discrete choice modeling. The framework considers travel patters of individuals and households that are simulated through a system of behavioral models that resemble commonly used travel demand models. In considering travel behavior of people, the framework is able to assess the impact of transport and urban planning policies according to how such policies address the needs and preferences of individuals. The innovation of this framework is in allowing accessibility-based assessment and policy evaluation by considering the urban transport system and the spatial arrangement and characteristics of land-uses together, and importantly, yet often neglected the socio-economic characteristics of the population. Based on the development and application of the accessibility framework, further research recommendations are discussed in the paper in order to improve the capability of accessibility for use as a tool by planners for identifying levels of accessibility and to develop and evaluate policies targeted towards improving accessibility for people arriving at their activities.

An Integrated Planning Tool for Evaluating Road Environmental Impacts

This article describes the theoretical foundation, fundamental structure, and application of an integrated planning tool for evaluating the multicriteria environmental sensitivity (ES) of urban road networks. The tool is an integration of the environmental sensitivity methodology (ESM) concept, analytic hierarchy process (AHP), fuzzy set theory (FST), knowledge-based expert systems (KBES), and geographic information system (GIS). A case study application of the tool, using the road network for the city of Geelong in Victoria, Australia, is described. The results of the case study indicate the potential utility of the tool for assessing the ES of an urban road network at a local level, identifying problem locations, and specifying the possible causes of those problems. In addition, it is found that the typical AHP expressed more powerful capability in differentiating links according to their composite ES characteristics than the fuzzy compositional AHP.