Intelligent Vehicle Highway Systems (IVHS), which aim at the utilization of advanced information processing and communication technologies for improving travel efficiency and safety, have become an important policy measure in recent years. One of their major components, Advanced Traveler Information Systems (ATIS), has been developed specifically to assist drivers in trip planning and decision making on destination selection, departure time, route choices and congestion avoidance.

Transportation planning has been turning away from the solutions of building highways and transit routes to changing people's travel choices and making more efficient use of existing facilities. With the recent research focus on Advanced Traveler Information Systems (ATIS), it is imperative to understand the travel behavior of people and the information required to change their travel choices.

In this paper we review attempts to develop CPM of individual travel behavior. CPM represent a linked set of computer programs together with appropriate databases which are designed to capture the essence of human decision making in different spatial situations. Used primarily for wayfinding and to simulate and predict travel behavior, CPMs bypass the difficult problems of IIA typically attributed to discrete choice models. They also allow greater emphasis on the cognitive components of decision making including cognitive maps, preferences, and departure from utility maximizing and linearity in the considerations of alternative paths and alternative destinations. The CPM illustrated herein focuses on multiperson households and models travel behavior before and after telecommuting takes place in the household° Sets of feasible alternative destinations for travel purposes are derived using GIS procedures such as buffering and path selection. Shortcomings and possible future developments of such models are then discussed.

The objective of the paper is to discuss the development of an alternative representation of the transportation network using object-oriented GIS. This representation is important for the supply side of transportation planning and modeling. Object-orientation provides a way of solving the problem in a planar network for routing. It can facilitate the calculation of detailed network characteristics using properties such as inheritance and polymorphism. This representation is also closer to human perception of a transportation network. It is argued that by using an object-oriented GIS we can facilitate path selection using different criteria. We experiment with the design of the object-oriented system by developing an object-oriented representation of a transportation network and incorporating different path selection algorithms based on various behavioral assumptions. It is especially useful in the design for a versatile ATIS.

Travel behavior entails several interrelated decisions made by people, as well as the execution of routines not preceded by deliberate decisions. Furthermore, travel decisions are dependent on choices to participate in activities. A conceptual framework is proposed as the basis of a computational-process model (CPM). Because of the complexity of the decision-making process in which individuals are engaged, CPMs are promising alternatives to disaggregate discrete choice modelling with its limited ability to account for interrelated decisions and its reliance on an unrealistic utility-maximizing framework. Empirical support for the proposed conceptual framework is presented in the paper from case studies of telecommuting households in Sacramento, CA. The value of geographical information systems (GIS) in these empirical tests is demonstrated.

The successful development of Intelligent Transportation Systems (ITS) depends on the capability of incorporating a vast amount of information about the location of facilities which generate travel as well as a realistic representation of elements of the transportation network in which travel occurs. An integral part of this system is an Advanced Traveler Information System (ATIS). Such a system can be based on an innovative and comprehensive Geographic Information System (GIS). Whereas current ITS primarily use simplified transportation networks as their basis, using an object-oriented GIS allows us to provide a more realistic representation of elements of the network and the ways that people perceive them. We can represent the network by defining roads or street hierarchies and by storing environmental data as layers which can be overlain, aggregated, or decomposed at will. Storing the transportation network as a hierarchy facilitates the calculation of different paths through the network and allows the introduction of different path selection criteria. A long-run aim of ITS is to develop a real time multi-strategy travel decision support system over a multi-modal network. We examine the advantages of an object-oriented system over the link-node system in pursing such a goal. We also identify, the shortcomings of link-node technology that are overcome by using an object-oriented data model. And finally, we discuss some of the theoretical and applied implications of our suggestions.

Travel behavior entails several interrelated decisions made by people, as well as the execution of routines not preceded by deliberate decisions. Furthermore, travel decisions are dependent on choices to participate in activities. After a brief review of research aiming at describing activity/travel patterns and approaches in which activity/travel decisions are modelled by means of discrete-choice modelling techniques, a conceptual framework is proposed as a background to an evaluation of several computational-process models. Further needed developments of these models are discussed, as well as the use of geographical information systems in their operationalization and application to traffic planning.

The objective of this paper is to review object-oriented (OO) approaches to data modeling and data handling and their usefulness in transportation planning and modeling in general and Intelligent Transportation Systems in particular. The paper begins with a discussion of the current GIS data model for representing a transportation network and the most common database management systems used in the context of transportation planning. We then discuss object-orientation, its different properties and its usefulness in representing a multi-modal, multi-scale network with hierarchical road types. We also discuss alternative database management schemes. Finally we review some existing systems and discuss the implications of adopting an object-oriented perspective.

Advanced Traveler Information Systems (ATIS) under the intelligent Vehicle Highway Systems (IVHS) context require efficient information retrieval and updating in a dynamic environment and at different geographical scales. Some problems in ATIS can be solved based on the functionalities provided by GIS systems. However, extra requirements such as real-time response are not readily met in existing GIS systems. We investigate the use of GIS-based systems for applications in ATIS and we propose a new system architecture based on existing GIS technology and distributed computing technology. Issues on data modeling, data representation, storage and retrieval, data aggregation, and parallel processing of on-line queries in the proposed GIS-based systems are discussed.

Models of households' travel choices are an important focus of research. For some time it has been realized that such models need to incorporate how travel depends on activity choices. It is argued that production system models constitute an alternative or necessary complementary approach if the goal is to develop models of interdependent activity and travel choices, or activity scheduling, which are based on behavioral-science theories of higher cognitive processes. Several computational-process models (CPMs) which implement production systems as computer programs are reviewed. Currently, no encompassing CPM exists but some may be possible to integrate in a descriptive model of activity scheduling.