An effective bridge management system that is equipped with reliable deterioration models enables agency engineers to carry out monitoring and long-term programming of bridge repair actions. At the project level, deterioration models help the agency to track the physical condition of bridge elements and to specify when bridge maintenance, rehabilitation and replacement can be expected. Also, with reliable deterioration models, the agency can customize bridge repair or replacement schedules that incorporate element condition, functional obsolescence, and pre-specified performance thresholds. At the network level, component-specific deterioration models are useful for system-wide needs assessment over a specified future time horizon, and to quantifying the system-wide consequences of funding shortfalls or funding increases in terms of specified performance measures including average values of bridge condition and remaining service life.

The bridge deterioration models that are currently in use in the Indiana Bridge Management System were developed over two decades ago. Since then, significant changes have taken place in inspection methods, technologies used, advanced statistical tools for data analysis. Also, because of the lack of reliable data, such items as the truck traffic and climate conditions were not included in past modeling efforts. In recent years, these obstacles have been minimized and therefore, there is an opportunity to update the deterioration models for the various bridge components.

In addressing this research need, the present study developed families of curves representing deterioration models for bridge deck, superstructure, and the substructure. The National Bridge Inventory database was used, and the models use the NBI condition ratings as the response variable. The model families were categorized by administrative region, functional class, and superstructure material type. The explanatory variables include traffic volume and truck traffic, design type, and climatic condition, and design features. Deterministic and probabilistic models were developed.

Report Number



bridge deterioration, National Bridge Inventory, bridge condition, bridge performance

SPR Number


Performing Organization

Joint Transportation Research Program

Publisher Place

West Lafayette, Indiana

Date of this Version