An Internet-based geographic information system that integrates data, models and users for transportation applications

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Abstract

This paper is concerned with the development of an Internet-based geographic information system (GIS) that brings together spatio-temporal data, models and users in a single efficient framework to be used for a wide range of transportation applications – planning, engineering and operational. The functional requirements of the system are outlined taking into consideration the various enabling technologies, such as Internet tools, large-scale databases and distributed computing systems. Implementation issues as well as the necessary models needed to support the system are briefly discussed.

Introduction

Transportation systems are complex entities that require substantial data to be monitored, controlled, maintained and improved, as well as various elaborate models to help a diverse group of agencies to operate the system. Data currently collected by transportation agencies can be loosely classified into the following types: planning, engineering and operational; a similar classification can be made for the models used. These data have certain similarities: (i) they are all concerned with the same network, traffic demand and control devices, albeit at different levels of aggregation and precision of representation, (ii) they are all spatio-temporal, i.e., they can be associated with spatial and temporal coordinates, (iii) they are often used by more than one models for different applications. Great benefits could be realized, if these data are integrated into a single database or linked distributed databases and become accessible by all necessary models. Data and models could, in turn, be available to all involved entities: planners, engineers, operators, as well as various stakeholders, such as researchers, consultants, trucking companies, special interest groups and even the traveling public.

Presently, transportation professionals have to cope with fragmented databases, multiple and incompatible models, redundant and often conflicting data acquisition efforts, lack of coordination between various agencies and private companies operating on the same transportation facilities. This results in serious inefficiencies and waste of resources. For example, a transportation planner uses the network of a metropolitan area for air quality analysis with a certain format that is usually incompatible with a signal optimization or simulation software that the traffic engineer of the same urban area uses to optimize the operations on the urban network. Typically, both professionals independently collect and code the data for the same network and demand (albeit at different aggregation levels) without taking advantage of the existing resources at each other's agency.

Enabling technologies developed over the past few years have created unprecedented opportunities to overcome some of the problems above. These technologies include the explosion of the Internet and Internet support tools, terabyte size databases, distributed computing architectures, client server technologies as well as a new generation of transportation tools resulted from the evolution of Intelligent Transportation Systems. Many of these technologies have already been adopted by corporations and have led into the development of new business models. In fact, from supply chain dynamics to customer relationship management to the enabling of an e-commerce infrastructure, the opportunity and need have never been greater to link business processes and people throughout an organization (Chambers, 1999). Internet-enabled geographic information system (GIS) has also attracted a lot of attention in the last few years: Jankowski and Stasik (1997) introduced an Internet-based GIS to make possible collaborative spatial decision making via public participation. Keisler and Sundell (1997) presented an integrated geographic multi-attribute utility system with application to park planning. An extensive survey of applications and research issues for geographic information technologies applications in business is provided in Mennecke (1997).

This paper introduces a prototype Internet-based GIS that aims to integrate spatio-temporal data and models for a wide range of transport applications: planning, engineering and operational. The GIS graphic user interface (GUI) is built in JAVA, so that it can be used over the Internet (or any other large network). The database efficiently stores and retrieves spatio-temporal data, by associating geographic coordinates and time stamps. The database is designed to efficiently manage a wide range of transport data: from off-line planning and engineering to streams of real-time, such as those coming in from street sensors and newer vehicle based devices. Furthermore, the control and encapsulation of the data that becomes possible with such a system, help deal with problems arising from agency specific requirements.

A number of models have been coded in the same framework and can by accessed via the GIS' GUI in a client server setting. The models can be remotely accessed via the GIS and run in a distributed environment based on the common object request broker architecture (CORBA). The implemented models include traditional signal control and analysis tools, planning models as well as newer dynamic traffic assignment (DTA) and routing algorithms. This paper discusses the interactions between the models, the potential efficiencies achieved by the integration of data and models, implementation difficulties as well as the implications to planning, engineering and operational practices. It should be noted that the primary focus is on the technical aspects of this integration and not on the institutional/policy issues even though the latter would obviously constrain the final system. Such issues, however, deserve attention, which is beyond the scope of this paper. Furthermore, due to the wide variety of policies and agencies, the introduced system is not currently presented in the context of any particular state agency or entity. Instead, the underlying characteristics of transportation data and models are examined in order to develop a system, which can later be placed within the institutional framework of a particular entity.

In the next section, we identify the needs and the functional requirements of the system. The overall model architecture is presented in Section 3. The models currently implemented or that need to be part of the framework are described in Section 4. Implementation details are provided in Section 5, including a justification for the Internet-based GUI and the distributed computing environment. Section 6 discusses the potential benefits that can be realized by the integration of the data, model and users. Section 7 concludes this paper and identifies directions for future research.

Section snippets

Needs and functional requirements

The transportation practice involves data, models and users. Data currently collected by transportation agencies can be loosely classified into the following types: planning, engineering and operational; a similar classification can be made for the models used. Planning data range from trip surveys, socioeconomic data by region and network infrastructure data, to aggregate daily link traffic flows. These data are used for long-range planning purposes, such as estimating the impact of

Overall approach and model architecture

The overall approach introduced in this paper was inspired of and is implemented according to practices adopted by the InfoTech (IT) Industry. The objective is to meet the functional requirements identified in the previous section and bring together data, models, users and applications into a seamless efficient, interwoven system. The introduced framework is called visual interactive system for transportation algorithms (VISTA). VISTA is a CORBA compliant distributed system accessible over a

Model structure

The primary modules currently implemented in the VISTA framework include a traffic simulator (RouteSim), traditional (static) planning models, DTA models, network routing algorithms, signal optimization models, ramp metering and incident management models. The interactions among models are coordinated by the central Management Module. Although each of these models may have different data type and structure requirements, the format for this data is kept uniform. The way in which the VISTA

Implementation of the distributed system

The client module has access to two primary framework resources: the Management and Database modules. Although a primary design principle for the framework is the centralization of all data within the database, certain temporary data can efficiently be communicated directly between modules via remote method processing. Since the Management Module must coordinate the execution of numerous algorithm modules and handle certain data elements, the robust CORBA protocol as specified by the OMG is

Challenges and expected benefits

No major technical challenges appear to exist for implementing and deploying the proposed framework, but quite a few institutional. The system requires close collaboration among many agencies and other entities that traditionally do not interact. It assumes also that certain organizations will relinquish control of data and will be asked to change certain practices. We recognize that this may be a formidable obstacle. However, the expected benefits are so obvious and substantial that as these

Conclusions

This paper introduced an integrated framework for transportation analysis, control and optimization algorithms that unifies several transportation tools so that they share a common data specification and user interface. The main focus is on interactions between data and models particular to transportation systems rather than specific issues of geographic representation. A mesoscopic traffic simulator (RouteSim), static traffic assignment, DTA, control, and routing algorithms have been

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