1. Introduction
A well-designed geographic information system (GIS) provides a platform on which all aspects of the PMS process can be built. The resulting system, GIS/PMS, represents a significant enhancement of all aspects of the PMS process. A variety of spatially integrated data are important to pavement management decision making. GIS technology is shown to be the most logical way of relating these diverse, but relevant, data. The components include data collection, preliminary data analysis and interpretation, system assessment, determination of strategies, project identification and development, and project implementation. Each of these stages in the PMS process is enhanced by GIS technology. Looking at the PMS process in its entirety leads to the enumeration of a set of functions to be embedded in the GIS platform that is required for effective GIS/PMS. These functions include thematic mapping, a flexible data base editor, formula editing, statistics, charting, matrix manipulation, network generation, models and algorithms, and hooks to external procedures.
2. Role of Spatially Integrated Data in PMS
Comprehensive pavement management models require a diverse collection of highway-related data including pavement condition surveys, skid resistance measurements, traffic counts, bridge inspections, sign inventories, photologging, accident investigation, construction and maintenance records and inventories of signs and roadside obstacles. Although these data may be available in digital format, they are typically unrelated to each other, duplicative and inconsistent. The various files may have been created independently of one another, using different referencing systems or computer formats. Popular referencing systems include milepost, reference post, paper document methods, state plane and latitude longitude. In the worst case, some of the data required for analysis may not be spatially referenced at all. As a result, they are difficult to use in a consistent and efficient manner as inputs to a PMS. GIS technology is proposed as a framework for data integration because it provides a means of relating data collected under various referencing systems.
3. GIS – PMS Integration Framework
As with any management process, pavement management needs a decision support system to be effective. The decision support system functions range from information retrieval and display, filtering and pattern recognition, extrapolation, inference and logical comparison, to complex modeling. A GIS can be a very important decision support system element by facilitating the preparation, analysis, display, and management of geographical data. In a PMS, a GIS can greatly enhance the analysis and presentation of information. Figure 1 shows the typical PMS structure for a local situation. The database is the first building block of any asset management system, and it must include, at a minimum, the following informations:
- Inventory – basic physical attributes of the road network being managed
- Pavement Condition – periodic functional and structural evaluations to assess the level of service being provided to the user, and
- Maintenance and Rehabilitation strategies – strategies the agency uses to correct the problems. These are determined using the periodic condition surveys.
The database information is then analyzed to produce a multiyear maintenance and rehabilitation work program and budget, as follows:
- Network needs – the system will first assign all the maintenance and rehabilitation strategies for each road section in the inventory and narrowed down to the best strategy
- Prioritization – since the resources available are usually less than what the system needs, the resulting projects are ranked based on criteria consistent with agency objectives;
- Work program – using the list of prioritized projects, a multiyear maintenance and rehabilitation program is prepared; and
- Budget – the annual financial needs for executing the projects included in the work program are defined.