Automated conversion of milepoint data to intersection/link structure:an application of GIS in transportation

Network data restructuring is an essential function in Geographic Information Systems (GIS) when adapted to transportation. Implementing effective data restructuring models in GIS allows users to collect and maintain data in the format with which they are most familiar while allowing others to utilize it in a format they require. Aggregation and disaggregation of network data facilitates storage, display and plotting times. There could however be important adverse effects. The effects of generalizing attribute data for aggregation/disaggregation is being researched here.

Milepoint referenced data in road inventory files provides valuable network information for transportation research. Individual records in these files represent variable length sections of roads. A new record is created each time a highway attribute changes. Consequently, a segment of road between two intersections may be represented by several records in a road inventory file. Further, all attributes in these records are associated with both directions of travel along a road.

Many transportation analysis models require networks to be represented by a node-link structure where nodes symbolize an intersection of two or more roads. Further, if a road is two directional, it is represented by two links each of which has its own set of attributes. To utilize road inventory data in these analysis models, network information has to be converted into an intersection/link format. This process involves aggregating· and disaggregating attribute data to represent longer and shorter road segments and also disaggregating data into bi-directional information.

This thesis describes data conversion efforts needed to produce intersectional-link network representations. The development of a microcomputer model for data conversion is detailed and application issues and model sensitivities are addressed.